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43.5: Human Pregnancy and Birth - Biology

43.5: Human Pregnancy and Birth - Biology



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Skills to Develop

  • Explain fetal development during the three trimesters of gestation
  • Describe labor and delivery
  • Compare the efficacy and duration of various types of contraception
  • Discuss causes of infertility and the therapeutic options available

Pregnancy begins with the fertilization of an egg and continues through to the birth of the individual. The length of time of gestation varies among animals, but is very similar among the great apes: human gestation is 266 days, while chimpanzee gestation is 237 days, a gorilla’s is 257 days, and orangutan gestation is 260 days long. The fox has a 57-day gestation. Dogs and cats have similar gestations averaging 60 days. The longest gestation for a land mammal is an African elephant at 640 days. The longest gestations among marine mammals are the beluga and sperm whales at 460 days.

Human Gestation

Twenty-four hours before fertilization, the egg has finished meiosis and becomes a mature oocyte. When fertilized (at conception) the egg becomes known as a zygote. The zygote travels through the oviduct to the uterus (Figure (PageIndex{1})). The developing embryo must implant into the wall of the uterus within seven days, or it will deteriorate and die. The outer layers of the zygote (blastocyst) grow into the endometrium by digesting the endometrial cells, and wound healing of the endometrium closes up the blastocyst into the tissue. Another layer of the blastocyst, the chorion, begins releasing a hormone called human beta chorionic gonadotropin (β-HCG) which makes its way to the corpus luteum and keeps that structure active. This ensures adequate levels of progesterone that will maintain the endometrium of the uterus for the support of the developing embryo. Pregnancy tests determine the level of β-HCG in urine or serum. If the hormone is present, the test is positive.

The gestation period is divided into three equal periods or trimesters. During the first two to four weeks of the first trimester, nutrition and waste are handled by the endometrial lining through diffusion. As the trimester progresses, the outer layer of the embryo begins to merge with the endometrium, and the placenta forms. This organ takes over the nutrient and waste requirements of the embryo and fetus, with the mother’s blood passing nutrients to the placenta and removing waste from it. Chemicals from the fetus, such as bilirubin, are processed by the mother’s liver for elimination. Some of the mother’s immunoglobulins will pass through the placenta, providing passive immunity against some potential infections.

Internal organs and body structures begin to develop during the first trimester. By five weeks, limb buds, eyes, the heart, and liver have been basically formed. By eight weeks, the term fetus applies, and the body is essentially formed, as shown in Figure (PageIndex{2}). The individual is about five centimeters (two inches) in length and many of the organs, such as the lungs and liver, are not yet functioning. Exposure to any toxins is especially dangerous during the first trimester, as all of the body’s organs and structures are going through initial development. Anything that affects that development can have a severe effect on the fetus’ survival.

During the second trimester, the fetus grows to about 30 cm (12 inches), as shown in Figure (PageIndex{3}). It becomes active and the mother usually feels the first movements. All organs and structures continue to develop. The placenta has taken over the functions of nutrition and waste and the production of estrogen and progesterone from the corpus luteum, which has degenerated. The placenta will continue functioning up through the delivery of the baby.

During the third trimester, the fetus grows to 3 to 4 kg (6 ½ -8 ½ lbs.) and about 50 cm (19-20 inches) long, as illustrated in Figure (PageIndex{4}). This is the period of the most rapid growth during the pregnancy. Organ development continues to birth (and some systems, such as the nervous system and liver, continue to develop after birth). The mother will be at her most uncomfortable during this trimester. She may urinate frequently due to pressure on the bladder from the fetus. There may also be intestinal blockage and circulatory problems, especially in her legs. Clots may form in her legs due to pressure from the fetus on returning veins as they enter the abdominal cavity.

Link to Learning

Visit this site to see the stages of human fetal development.

Labor and Birth

Labor is the physical efforts of expulsion of the fetus and the placenta from the uterus during birth (parturition). Toward the end of the third trimester, estrogen causes receptors on the uterine wall to develop and bind the hormone oxytocin. At this time, the baby reorients, facing forward and down with the back or crown of the head engaging the cervix (uterine opening). This causes the cervix to stretch and nerve impulses are sent to the hypothalamus, which signals for the release of oxytocin from the posterior pituitary. The oxytocin causes the smooth muscle in the uterine wall to contract. At the same time, the placenta releases prostaglandins into the uterus, increasing the contractions. A positive feedback relay occurs between the uterus, hypothalamus, and the posterior pituitary to assure an adequate supply of oxytocin. As more smooth muscle cells are recruited, the contractions increase in intensity and force.

There are three stages to labor. During stage one, the cervix thins and dilates. This is necessary for the baby and placenta to be expelled during birth. The cervix will eventually dilate to about 10 cm. During stage two, the baby is expelled from the uterus. The uterus contracts and the mother pushes as she compresses her abdominal muscles to aid the delivery. The last stage is the passage of the placenta after the baby has been born and the organ has completely disengaged from the uterine wall. If labor should stop before stage two is reached, synthetic oxytocin, known as Pitocin, can be administered to restart and maintain labor.

An alternative to labor and delivery is the surgical delivery of the baby through a procedure called a Caesarian section. This is major abdominal surgery and can lead to post-surgical complications for the mother, but in some cases it may be the only way to safely deliver the baby.

The mother’s mammary glands go through changes during the third trimester to prepare for lactation and breastfeeding. When the baby begins suckling at the breast, signals are sent to the hypothalamus causing the release of prolactin from the anterior pituitary. Prolactin causes the mammary glands to produce milk. Oxytocin is also released, promoting the release of the milk. The milk contains nutrients for the baby’s development and growth as well as immunoglobulins to protect the child from bacterial and viral infections.

Contraception and Birth Control

The prevention of a pregnancy comes under the terms contraception or birth control. Strictly speaking, contraception refers to preventing the sperm and egg from joining. Both terms are, however, frequently used interchangeably.

Table (PageIndex{1}): Contraceptive Methods

MethodExamplesFailure Rate in Typical Use Over 12 Months
Barriermale condom, female condom, sponge, cervical cap, diaphragm, spermicides15 to 24%
Hormonaloral, patch, vaginal ring8%
injection3%
implantless than 1%
Othernatural family planning12 to 25%
withdrawal27%
sterilizationless than 1%

Table (PageIndex{1}) lists common methods of contraception. The failure rates listed are not the ideal rates that could be realized, but the typical rates that occur. A failure rate is the number of pregnancies resulting from the method’s use over a twelve-month period. Barrier methods, such as condoms, cervical caps, and diaphragms, block sperm from entering the uterus, preventing fertilization. Spermicides are chemicals that are placed in the vagina that kill sperm. Sponges, which are saturated with spermicides, are placed in the vagina at the cervical opening. Combinations of spermicidal chemicals and barrier methods achieve lower failure rates than do the methods when used separately.

Nearly a quarter of the couples using barrier methods, natural family planning, or withdrawal can expect a failure of the method. Natural family planning is based on the monitoring of the menstrual cycle and having intercourse only during times when the egg is not available. A woman’s body temperature may rise a degree Celsius at ovulation and the cervical mucus may increase in volume and become more pliable. These changes give a general indication of when intercourse is more or less likely to result in fertilization. Withdrawal involves the removal of the penis from the vagina during intercourse, before ejaculation occurs. This is a risky method with a high failure rate due to the possible presence of sperm in the bulbourethral gland’s secretion, which may enter the vagina prior to removing the penis.

Hormonal methods use synthetic progesterone (sometimes in combination with estrogen), to inhibit the hypothalamus from releasing FSH or LH, and thus prevent an egg from being available for fertilization. The method of administering the hormone affects failure rate. The most reliable method, with a failure rate of less than 1 percent, is the implantation of the hormone under the skin. The same rate can be achieved through the sterilization procedures of vasectomy in the man or of tubal ligation in the woman, or by using an intrauterine device (IUD). IUDs are inserted into the uterus and establish an inflammatory condition that prevents fertilized eggs from implanting into the uterine wall.

Compliance with the contraceptive method is a strong contributor to the success or failure rate of any particular method. The only method that is completely effective at preventing conception is abstinence. The choice of contraceptive method depends on the goals of the woman or couple. Tubal ligation and vasectomy are considered permanent prevention, while other methods are reversible and provide short-term contraception.

Termination of an existing pregnancy can be spontaneous or voluntary. Spontaneous termination is a miscarriage and usually occurs very early in the pregnancy, usually within the first few weeks. This occurs when the fetus cannot develop properly and the gestation is naturally terminated. Voluntary termination of a pregnancy is an abortion. Laws regulating abortion vary between states and tend to view fetal viability as the criteria for allowing or preventing the procedure.

Infertility

Infertility is the inability to conceive a child or carry a child to birth. About 75 percent of causes of infertility can be identified; these include diseases, such as sexually transmitted diseases that can cause scarring of the reproductive tubes in either men or women, or developmental problems frequently related to abnormal hormone levels in one of the individuals. Inadequate nutrition, especially starvation, can delay menstruation. Stress can also lead to infertility. Short-term stress can affect hormone levels, while long-term stress can delay puberty and cause less frequent menstrual cycles. Other factors that affect fertility include toxins (such as cadmium), tobacco smoking, marijuana use, gonadal injuries, and aging.

If infertility is identified, several assisted reproductive technologies (ART) are available to aid conception. A common type of ART is in vitro fertilization (IVF) where an egg and sperm are combined outside the body and then placed in the uterus. Eggs are obtained from the woman after extensive hormonal treatments that prepare mature eggs for fertilization and prepare the uterus for implantation of the fertilized egg. Sperm are obtained from the man and they are combined with the eggs and supported through several cell divisions to ensure viability of the zygotes. When the embryos have reached the eight-cell stage, one or more is implanted into the woman’s uterus. If fertilization is not accomplished by simple IVF, a procedure that injects the sperm into an egg can be used. This is called intracytoplasmic sperm injection (ICSI) and is shown in Figure (PageIndex{5}). IVF procedures produce a surplus of fertilized eggs and embryos that can be frozen and stored for future use. The procedures can also result in multiple births.

Summary

Human pregnancy begins with fertilization of an egg and proceeds through the three trimesters of gestation. The labor process has three stages (contractions, delivery of the fetus, expulsion of the placenta), each propelled by hormones. The first trimester lays down the basic structures of the body, including the limb buds, heart, eyes, and the liver. The second trimester continues the development of all of the organs and systems. The third trimester exhibits the greatest growth of the fetus and culminates in labor and delivery. Prevention of a pregnancy can be accomplished through a variety of methods including barriers, hormones, or other means. Assisted reproductive technologies may help individuals who have infertility problems.

Review Questions

Nutrient and waste requirements for the developing fetus are handled during the first few weeks by:

  1. the placenta
  2. diffusion through the endometrium
  3. the chorion
  4. the blastocyst

B

Progesterone is made during the third trimester by the:

  1. placenta
  2. endometrial lining
  3. chorion
  4. corpus luteum

A

Which contraceptive method is 100 percent effective at preventing pregnancy?

  1. condom
  2. oral hormonal methods
  3. sterilization
  4. abstinence

D

Which type of short term contraceptive method is generally more effective than others?

  1. barrier
  2. hormonal
  3. natural family planning
  4. withdrawal

B

Which hormone is primarily responsible for the contractions during labor?

  1. oxytocin
  2. estrogen
  3. β-HCG
  4. progesterone

A

Major organs begin to develop during which part of human gestation?

  1. fertilization
  2. first trimester
  3. second trimester
  4. third trimester

B

Free Response

Describe the major developments during each trimester of human gestation.

The first trimester lays down the basic structures of the body, including the limb buds, heart, eyes, and the liver. The second trimester continues the development of all of the organs and systems established during the first trimester. The placenta takes over the production of estrogen and high levels of progesterone and handles the nutrient and waste requirements of the fetus. The third trimester exhibits the greatest growth of the fetus, culminating in labor and delivery.

Describe the stages of labor.

Stage one of labor results in the thinning of the cervix and the dilation of the cervical opening. Stage two delivers the baby, and stage three delivers the placenta.

Glossary

contraception
(also, birth control) various means used to prevent pregnancy
gestation
length of time for fetal development to birth
human beta chorionic gonadotropin (β-HCG)
hormone produced by the chorion of the zygote that helps to maintain the corpus luteum and elevated levels of progesterone
infertility
inability to conceive, carry, and deliver children
morning sickness
condition in the mother during the first trimester; includes feelings of nausea
placenta
organ that supports the diffusion of nutrients and waste between the mother’s and fetus’ blood

Multilingual Illustrated DVD [Tutorial]

Introducing the Multilingual Illustrated DVD
Explore the fascinating imagery and facts presented in The Biology of Prenatal Development at your own pace. Each clip from the program is accompanied by its corresponding written script. Select Play Movie to watch any clip. Select See Snapshots to view high resolution images. See the program script and subtitles in 88 languages by using the Choose Language drop-down menu and clicking Refresh. Subtitles are displayed in your chosen language and may be turned on and off by clicking the button found in the lower right corner of the movie player. A "full screen" option is also available by clicking the button.

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Table of Contents

Chapter 1 Introduction

The dynamic process by which the single-cell human zygote becomes a 100-trillion-cell adult is perhaps the most remarkable phenomenon in all of nature.

Researchers now know that many of the routine functions performed by the adult body become established during pregnancy - often long before birth.

Chapter 2 Terminology

Pregnancy in humans normally lasts approximately 38 weeks as measured from the time of fertilization, or conception, until birth.

During the first 8 weeks following fertilization, the developing human is called an embryo, which means "growing within." This time, called the embryonic period, is characterized by the formation of most major body systems.

From the completion of 8 weeks until the end of pregnancy, "the developing human is called a fetus," which means "unborn offspring." During this time, called the fetal period, the body grows larger and its systems begin to function.


Babies After 40: The Hidden Health Risks of Mid-Life Pregnancy

After years of struggling with repeated miscarriages and fertility treatments, including in vitro fertilization (IVF), Joanna Brody was thrilled when she finally conceived on her own at the age of 43𠅎ven considering the increased risk of health problems associated with pregnancy after age 40. Still, the former marathon runner was in good health and exercised throughout her pregnancy, which was uneventful.

But two days after returning home from the hospital after her daughters birth (she also had a 6-month-old adopted son), she woke up feeling like she couldnt breathe. “I thought I was having a panic attack due to the stress of taking care of two infants while building a new home,” Brody, now 45, recalls.

The next day, when she couldnt catch her breath walking up a flight of stairs, she rushed to the emergency room. There, doctors discovered that her lungs were filled with fluid, a sign of peripartum cardiomyopathy, a potentially fatal condition that occurs when theres damage to the heart, resulting in a weakened heart muscle that can&apost pump blood efficiently. While it occurs in only about 1 in every 1,300 deliveries, its most common in older women, especially those, like Brody, who are over the age of 40.

The number of women giving birth into their 40s and 50s and beyond is at record highs, according to the Centers for Disease Control and Prevention. In 2007, 105,071 women aged 40-44 gave birth, the highest rate since 1968 the birth rate for women 45 to 54 was 7,349, an increase of 5% in just one year.

“The numbers have really skyrocketed over the last two decades, as research has increasingly shown that older women are able to carry pregnancies and deliver babies safely,” says Mark Sauer, MD, chief of reproductive endocrinology at Columbia University Medical Center and a leading researcher in this field.

Success stories
Theres no official data on how many American women over the age of 54 successfully give birth each year, although there have been plenty of news reports of women in their late 50s and early 60s who have conceived via donor eggs. While older moms have long been the source of biblical legend (think of Sarah, who is said to have given birth to her husband Abrahams son Isaac at the jaw-dropping age of 90), right now the oldest documented birth mother in the world is Omkari Panwar, a 70-year-old Indian woman who gave birth to 2-pound twins in 2008 via emergency cesarean section.

But the United States has had its share of 60-plus new moms, too, including Frieda Birnbaum of Saddle River, New Jersey, who in 2007 at age 60 set the record for the oldest woman in the country to give birth to twins. (A 62-year-old, Janise Wulf, gave birth to a singleton in 2006.)

While it may seem nothing short of miraculous that cutting-edge IVF technology is enabling older women to get pregnant, experts are concerned about the increased risk of maternal health problems, ranging from cardiac complications to potentially even a higher risk of developing breast cancer.

𠇊 healthy 42-year-old with no medical problems who is in good physical shape and conceives naturally is likely to have just as nice a pregnancy as a woman who is a decade younger,” says Laura Riley, MD, a maternal-fetal-medicine specialist at Massachusetts General Hospital and chairwoman of the communications committee of the Society of Maternal-Fetal Medicine. 𠇋ut there are a fair number of women in their mid-40s getting pregnant through IVF who have a ‘touch of hypertension, are a little overweight, or are prediabetic, and that&aposs where we start running into problems.”

Older women are increasingly at risk for potentially deadly complications. A 2002 University of Southern California study, for example, found that 26% of women ages 50 to 54 suffered from preeclampsia (a life-threatening condition characterized by high blood pressure and protein in the urine), and 13% developed gestational diabetes (a temporary form of diabetes that occurs during pregnancy)𠅊nd that number soared to 60% and 40%, respectively, for those over the age of 55.

While there are no official guidelines from organizations like the American Society for Reproductive Medicine on how old is too old, leading fertility experts and high-risk obstetricians are voicing concerns about this brave new world of peri- and postmenopausal pregnancy.

“The age cutoff at our clinic is 54, based on the research that shows a marked increase in complications in women older than 55,” says Richard Paulson, MD, director of the Fertility Program at the University of Southern California Keck School of Medicine and one of the countrys leading researchers on pregnancy in the peri- and postmenopausal years.

Others are more conservative. “We have an age cutoff in our practice of 44 years of age for someone using her own eggs and 51 years of age in someone using donor eggs,” says Robert Stillman, MD, medical director of Shady Grove Fertility Center, one of the countrys largest fertility clinics, with 15 offices in the Washington, D.C., area. “Weve never had a successful birth in a woman over the age of 44 using her own eggs, and we think its unethical to promote treatments in a vulnerable population where theres not a chance of success. We won&apost treat women over the age of 51, period, because we believe there are too many risks involved with carrying the pregnancy, both for the mother and for the fetus.”

But many clinics across the United States—including some of the nations leading fertility centers—take women who are well into their 50s. So what are these risks, and what exactly do they mean for older wom૞n who are contemplating pregnancy? Here, a look at the biggest dangers.

The risk of cancer
One can&apost help thinking of Elizabeth Edwards, who gave birth to two children at ages 48 and 50 after undergoing fertility treatments𠅊nd who was diagnosed four years later, in 2004 at the age of 55, with stage II breast cancer. (In 2007, she revealed that her cancer had recurred and was now at stage IV.)

While she has never publicly discussed whether there could be a link between fertility treatments in older moms and subsequent breast cancer, breast cancer experts speculate that the two could be related.

“Its a very unsettled question,” says Julia Smith, MD, PhD, director of the Lynne Cohen Breast Cancer Preventive Care Program at the New York University Cancer Institute. 𠇎very time weve tampered with the natural cycle of reproductive hormones, weve had a problem, as evidenced by research showing a link between hormone replacement therapy and breast cancer. As women get older, theyre at increased risk for breast cancer, and Im concerned about giving peri- or postmenopausal women additional sex hormones that could disrupt the natural course of aging of the breast cell.”

Research also shows that older women who have recently given birth are more likely to develop breast cancer in the 15 years following the birth than their peers of the same age who have never had children. One Swedish study followed women after theyd given birth and found that the childbearing women were slightly more likely to be diagnosed with cancer𠅊nd women who had their first child after the age of 35 had the highest risk, about 26% higher than women who had never given birth. (This is a transient risk: After 15 years, their odds dropped below that of women who had never given birth.)

“My worry is if an older woman is cooking a really early breast cancer and then is exposed to massive levels of estrogen during her pregnancy, could that accelerate tumor growth?” adds Mary Jane Minkin, MD, professor of obstetrics and gynecology at the Yale School of Medicine. “No ones ever studied it, and its a real possibility.”

The other point of concern: “The minute a woman gets pregnant, we can&apost screen her for breast cancer. And we can&apost do a mammogram until she&aposs finished breast-feeding, which could be almost two years later,” Dr. Smith points out. “If she&aposs younger than 40, its not a big issue because her overall risk of breast cancer is so low. But if she&aposs 45 or 50, then Im worried.”

Cancer experts are less concerned about the risks of other types of reproductive cancers among past-40 women undergoing fertility treatments. In fact, a Danish study published in February in the British Medical Journal followed more than 50,000 women who underwent fertility treatments for 15 years and found no increased risk of ovarian cancer among women who took most types of fertility drugs.

The one exception—women who took clomiphene citrate (Clomid) had an increased risk of a type of ovarian tumor called serous ovarian tumors, which may be more influenced by hormones than other tumors, says Louise Brinton, PhD, chief of the Hormonal and Reproductive Epidemiology Branch at the National Cancer Institute. Brintons own preliminary research has found a possible link between Clomid and endometrial cancer, a treatable cancer of the womb. “Many women in their 40s and 50s are using donor eggs, so they won&apost be taking Clomid, which is an ovulation-inducing drug,” she points out. 𠇋ut for those women who are, they need to be aware that there may be a link.”

The problem is, many women aren&apost briefed by their doctors on potential long-term risks. “I talk to fertility specialists all the time and bring up my concerns, and they tell me the same thing they tell their patients—they dont have any evidence that it is harmful,” Dr. Smith adds. 𠇋ut its not a question of not having evidence proving harm—we dont have any evidence proving safety.”

The risk to your heart
The strain of pregnancy, experts say, can be likened to the stress of running a marathon𠅊nd the older a woman is, the more likely she is to have complications from it.

Doctors of women in the 40-plus set are most concerned about pregnancy-induced pre귬lampsia, which generally surfaces in the third trimester. While the incidence of preeclampsia among all moms-to-be is 3 to 4%, that risk increases to 5 to 10% if you&aposre older than 40 and jumps up to 35% if you&aposre past 50. Most reputable fertility clinics require patients over the age of 45, especially those with borderline cholesterol or high blood pressure, to undergo more extensive cardiology screening, like an electrocardiogram (EKG) or a stress test, but “these tests can miss women who have borderline heart disease,” Dr. Stillman says. “Sure, they may be fine playing tennis. But the stress of nine months of pregnancy? That&aposs the equivalent of climbing Mt. Kilimanjaro.”

In addition, pregnancy can prompt an earlier onset of health problems that would have otherwise developed later in life. 𠇊 50-year-old woman with borderline high blood pressure who might not develop hypertension until she&aposs 60 may start to have it during her pregnancy,” explains Errol Norwitz, MD, a high-risk OB-GYN at the Yale School of Medicine. And this can set her and her baby up for a host of complications.

Deborah Lake, 50, developed preeclampisa seven years ago (she was 43) while carrying twins, prompting her physician to induce labor. “My blood pressure had always been quite low, but toward the end it began to creep up to the point where my doctor decided to induce me at 36 1/2 weeks,” she recalls. Lake delivered her first daughter, Savannah, vaginally. But her second daughter, Courtney, got stuck in the birth canal, prompting an emergency C-section. Lake was discharged after three days, only to return a few days later when her blood pressure shot up and her whole body swelled, both signs of preeclampsia. “They gave me diuretics, and I peed out about 50 pounds of water weight in three days,” she recalls.

Lake had been trying to get pregnant for almost a decade and finally conceived via donor eggs. �use of my age and the fact that I was carrying twins, I was so careful—I ate perfectly, I didnt gain too much weight,” she says. 𠇋ut even that, ultimately, wasnt enough to stave off problems.”

There are also heart concerns after pregnancy. “Most women tend to gain weight with each pregnancy and keep those extra 10 pounds around for a while,” Dr. Minkin says. “That extra weight increases an older womans risk of developing heart disease.”

Progesterone, a reproductive hormone that&aposs given to women during IVF and is also present at high levels during pregnancy, causes both blood pressure and cholesterol to temporarily go up, adds Nieca Goldberg, MD, director of the New York University Womens Heart Center. “This isnt an issue for a healthy woman with no risk factors for heart disease.

But if you&aposre going into pregnancy with borderline high blood pressure or cholesterol, which many older women have, it can pose a serious problem,” she says.

Peripartum cardiomyopathy, which Joanna Brody had, is also a potential danger among this group of moms. While Brody emerged unscathed, this condition can cause heart failure—which leads to death in 25 to 50% of cases, according to the National Institutes of Health.

Another huge worry: gestational diabetes, a temporary form of diabetes that occurs during pregnancy. It almost always goes away after delivery, but it can be a harbinger of diabetes later in life and puts women at risk for delivering a too-large baby (macrosomia).

Though the overall rate of gestational diabetes is 3%, it rises to 7% in women older than 40 and 20% in women older than 50. But while risk factors like a family history of diabetes, borderline blood sugars, being overweight, or having had gestational diabetes in an earlier pregnancy all increase your chances of getting it, many older women with none of these end up developing this dangerous condition.

Not surprisingly, because over-40 women are more at risk for a variety of health problems, their C-section rate is significantly higher than that of younger moms. Almost a third of all women in the United States deliver via C-section, but almost 50% of women having their first child between 40 to 45 and almost 80% in women ages 50 to 63 undergo the procedure.

“Older women have older uteruses, which tend to not contract as well, which can result in abnormal labor” and lead to a C-section, explains Robin Kalish, MD, director of clinical maternal-fetal medicine at Weill Cornell Medical Center in New York City.

The risk of placental problems
While placental problems are relatively rare during pregnancy, the risk shoots up once you hit the big 4-0. If you get pregnant past that age, you have a 10-fold increased risk, compared with women younger than 30, of placenta previa𠅊 dangerous condition in which the placenta does not move up and away from the opening of the uterus during pregnancy this can cause severe vaginal bleeding and activate premature labor. The main reason? An older uterus is less hospitable to the drastic bodily changes of pregnancy.

“The uterus is required to grow from the size of a small pear to a huge watermelon in nine months, which requires an enormous level of blood flow,” Dr. Stillman says. “Vascular disease is ubiquitous as people age, whether its in the heart or in the vagina, and it gets more and more difficult as a woman gets older for her uterus to keep up with the rapid growth of pregnancy.”

Lauren B. Cohen, a New Jersey lawyer who is the second oldest woman in the United States to give birth to twins, at age 59, spent two months in the hospital before giving birth to her twins at 31 1/2 weeks due to complications from placenta percreta, an incredibly rare condition in which the placenta actually breaks through the walls of the uterus and attaches to another organ such as the bladder.

“My doctors said my uterine walls had been weakened, due to age, a past C-section, and the stress of carrying twins,” Cohen explains. During the C-section, she hemorrhaged so much from her placenta that she required a transfusion of 33 units of blood. The twins𠅋orn two months premature at just over 3 pounds each—have suffered no long-term health problems, but they have developmental delays.

The risk to baby
Babies born to over-40 women like Cohen are not only more likely to be born early but also more likely to have birth defects. One Columbia University study found that 2.9% of women older than 40 have babies with birth defects, compared with 1.7% of all women younger than 35. Of these, cardiac issues are the most common: Another study found that heart defects were four times more common in infants of women over 40, compared with those age 20 to 24.

“It could have something to do with egg quality or with the fact that older women may have undiagnosed and untreated diabetes or hypertension, which could affect growth and contribute to birth defects,” explains Randy Fink, MD, a high-risk OB-GYN in Miami.

What women must know
While modern medicine is now able to get you pregnant into your fourth, fifth, or even sixth decade, it can&apost guarantee a smooth and safe road to delivery. There are undeniable health risks to pregnancy in the peri- and postmenopausal years, risks that often aren&apost revealed to the plus-40 women hoping to get pregnant. If you&aposre in your 40s and considering pregnancy, its critical to be proactive and get a thorough screening to rule out hidden heart disease or diabetes.

𠇊ll women in this age group need to get their blood pressure, cholesterol, and blood sugar levels checked, as well as an EKG,” before trying to get pregnant, Dr. Goldberg says. While a borderline or high level on any of these tests doesn&apost necessarily rule out pregnancy, you&aposll need to undergo even more detailed tests such as an echocardiogram, which uses sound waves to “see” any potential damage done already to your heart.

Women with risk factors for breast cancer——such as having a family history of the disease——should also think carefully before proceeding, Dr. Smith advises. Most women over the age of 45 are automatically referred to a high-risk practice. If you&aposre not, make sure you get a recommendation for a good one.

The bottom line: It is possible to have a baby in midlife. But before you proceed, its essential to understand the potential dangers to you and your baby.

𠇎ven if a woman passes all the screening tests with flying colors, she&aposs still more at risk for health complications,” stresses Miriam Greene, MD, an OB-GYN at New York University Langone Medical Center. 𠇊nd we just don&apost know what the long-term health effects are going to be of all these added hormones on their bodies. If an older woman decides she wants to get pregnant, that&aposs her decision. But she should have her eyes wide open and make sure she&aposs fully aware of all the potential risks.”


Labor is the physical efforts of expulsion of the fetus and the placenta from the uterus during birth (parturition). Toward the end of the third trimester, estrogen causes receptors on the uterine wall to develop and bind the hormone oxytocin. At this time, the baby reorients, facing forward and down with the back or crown of the head engaging the cervix (uterine opening). This causes the cervix to stretch and nerve impulses are sent to the hypothalamus, which signals for the release of oxytocin from the posterior pituitary. The oxytocin causes the smooth muscle in the uterine wall to contract. At the same time, the placenta releases prostaglandins into the uterus, increasing the contractions. A positive feedback relay occurs between the uterus, hypothalamus, and the posterior pituitary to assure an adequate supply of oxytocin. As more smooth muscle cells are recruited, the contractions increase in intensity and force.

There are three stages to labor. During stage one, the cervix thins and dilates. This is necessary for the baby and placenta to be expelled during birth. The cervix will eventually dilate to about 10 cm. During stage two, the baby is expelled from the uterus. The uterus contracts and the mother pushes as she compresses her abdominal muscles to aid the delivery. The last stage is the passage of the placenta after the baby has been born and the organ has completely disengaged from the uterine wall. If labor should stop before stage two is reached, synthetic oxytocin, known as Pitocin, can be administered to restart and maintain labor.

An alternative to labor and delivery is the surgical delivery of the baby through a procedure called a Caesarian section. This is major abdominal surgery and can lead to post-surgical complications for the mother, but in some cases it may be the only way to safely deliver the baby.

The mother’s mammary glands go through changes during the third trimester to prepare for lactation and breastfeeding. When the baby begins suckling at the breast, signals are sent to the hypothalamus causing the release of prolactin from the anterior pituitary. Prolactin causes the mammary glands to produce milk. Oxytocin is also released, promoting the release of the milk. The milk contains nutrients for the baby’s development and growth as well as immunoglobulins to protect the child from bacterial and viral infections.


Contraception and Birth Control

The prevention of a pregnancy comes under the terms contraception or birth control. Strictly speaking, contraception refers to preventing the sperm and egg from joining. Both terms are, however, frequently used interchangeably.

Table 1. Contraceptive Methods
Method Examples Failure Rate in Typical Use Over 12 Months
Barrier male condom, female condom, sponge, cervical cap, diaphragm, spermicides 12-21%
Hormonal oral, patch, vaginal ring 7%
injection 4%
implant, some intrauterine devices less than 1%
Other natural family planning 2 to 23%
withdrawal 27%
sterilization, some intrauterine devices less than 1%
modified from Trussell J et al. eds. Contraceptive technology. 21st ed. New York, NY: Ayer Company Publishers, Inc., 2018.

Table 1 lists common methods of contraception. The failure rates listed are not the ideal rates that could be realized, but the typical rates that occur. A failure rate is the number of pregnancies resulting from the method’s use over a twelve-month period. Barrier methods, such as condoms, cervical caps, and diaphragms, block sperm from entering the uterus, preventing fertilization. Spermicides are chemicals that are placed in the vagina that kill sperm. Sponges, which are saturated with spermicides, are placed in the vagina at the cervical opening. Combinations of spermicidal chemicals and barrier methods achieve lower failure rates than do the methods when used separately.

Nearly a quarter of the couples using barrier methods, natural family planning, or withdrawal can expect a failure of the method. Natural family planning is based on the monitoring of the menstrual cycle and having intercourse only during times when the egg is not available. A female’s body temperature may rise a degree Celsius at ovulation and the cervical mucus may increase in volume and become more pliable. These changes give a general indication of when intercourse is more or less likely to result in fertilization. Withdrawal involves the removal of the penis from the vagina during intercourse, before ejaculation occurs. This is a risky method with a high failure rate due to the possible presence of sperm in the bulbourethral gland’s secretion, which may enter the vagina prior to removing the penis.

Hormonal methods use synthetic progesterone (sometimes in combination with estrogen), to inhibit the hypothalamus from releasing FSH or LH, and thus prevent an egg from being available for fertilization. The method of administering the hormone affects failure rate. The most reliable method, with a failure rate of less than 1 percent, is the implantation of the hormone under the skin. The same rate can be achieved through the sterilization procedures of vasectomy in the male or of tubal ligation in the female, or by using an intrauterine device (IUD). IUDs are inserted into the uterus and establish an inflammatory condition that prevents fertilized eggs from implanting into the uterine wall. Some IUDs also prevent ovulation, or prevent sperm from entering the cervix and uterus.

Compliance with the contraceptive method is a strong contributor to the success or failure rate of any particular method. The only method that is completely effective at preventing conception is abstinence. The choice of contraceptive method depends on the goals of the female or couple. Tubal ligation and vasectomy are considered permanent prevention, while other methods are reversible and provide short-term contraception.

Termination of an existing pregnancy can be spontaneous or voluntary. Spontaneous termination is also known as miscarriage and usually occurs very early in the pregnancy, usually within the first few weeks. This occurs when the fetus cannot develop properly and the gestation is naturally terminated, and is very common. About one fifth of all clinically recognized pregnancies end in spontaneous termination. Voluntary termination of a pregnancy is referred to as abortion. Laws regulating abortion vary between states and tend to view fetal viability as the criteria for allowing or preventing the procedure.


Human Reproductive Cycle

The reproductive structures of many animals are very similar, even across different lineages, in a process that begins with two gametes–eggs and sperm–and ends with a zygote, which is a fertilized egg. In animals ranging from insects to humans, males produce sperm in testes and sperm are stored in the epididymis until ejaculation. Sperm are small, mobile, low-cost cells that occur in high numbers. Females produce an ovum or egg that matures in the ovary. Eggs are large cells that require a substantial investment of time and energy to form, are non-mobile, and are rare relative to sperm numbers. When the eggs are released from the ovary, they travel to the uterine tubes for fertilization (in animals that reproduce via internal fertilization) or are released in the aqueous environment (in animals that reproduce via external fertilization).

The first half of Hank Green’s Crash course video below has a nice summary of these ideas for a diversity of eukaryotes, while the second half of the video introduces the human reproductive anatomy before we take a deeper dive into the structures and functions via dynamic hormonal changes.

For our purposes, all sexual reproducers have females with ovaries that produce large eggs, which subsequently travel down a uterine tube, and males with testes that produce small, plenteous sperm, stored in an epididymus. Of course, beyond this general anatomy, there are some differences in different types of animals:

  • In many insects and some mollusks and worms, the female has a specialized sac, the spermatheca, which stores sperm for later use, sometimes up to a year. Fertilization can be timed with environmental or food conditions that are optimal for offspring survival.
  • Non-mammal vertebrates, such as most birds and reptiles, have a cloaca, a single body opening for the digestive, excretory, and reproductive systems. Mating between birds usually involves positioning the cloaca openings opposite each other for transfer of sperm from male to female. Ducks are a rare exception, where the males have a penis.
  • Mammals have separate openings for digestive, excretory, and reproductive systems in the female, and placental mammals have a uterus where offspring develop.

The remainder of today’s content focus on human reproduction and include structures as well as hormonal control. We will provide a list of the anatomy you need to know and would like you to focus on the hormones and how they work together to support effective reproduction. Hormones are dynamic (changing), so this process can be trickier to understand. Hormonal changes are the center of the fascinating biology of reproduction.


Section Summary

Human pregnancy begins with fertilization of an egg and proceeds through the three trimesters of gestation. The labor process has three stages (contractions, delivery of the fetus, expulsion of the placenta), each propelled by hormones. The first trimester lays down the basic structures of the body, including the limb buds, heart, eyes, and the liver. The second trimester continues the development of all of the organs and systems. The third trimester exhibits the greatest growth of the fetus and culminates in labor and delivery. Prevention of a pregnancy can be accomplished through a variety of methods including barriers, hormones, or other means. Assisted reproductive technologies may help individuals who have infertility problems.


Contents

In human medicine, "gravidity" refers to the number of times a woman has been pregnant, [1] regardless of whether the pregnancies were interrupted or resulted in a live birth:

  • The term "gravida" can be used to refer to a pregnant woman.
  • A "nulligravida" is a woman who has never been pregnant.
  • A "primigravida" is a woman who is pregnant for the first time or has been pregnant once.
  • A "multigravida" or "secundigravida" is a woman who has been pregnant more than once.

Terms such as "gravida 0", referring to a nulligravida, "gravida 1" for a primigravida, and so on, can also be used. The term "elderly primigravida" has also been used to refer to a woman in their first pregnancy who is at least 35 years old. [4] Advanced maternal age can be a risk factor for some birth defects.

In biology, the term "gravid" (Latin: gravidus "burdened, heavy" [5] ) is used to describe the condition of an animal (most commonly fish or reptiles) when carrying eggs internally. For example, Astatotilapia burtoni females can transform between reproductive states, one of which is gravid, and the other non-gravid. In entomology it describes a mated female insect.

In human medicine, parity is the number of pregnancies carried by a woman for at least 20 weeks (duration varies from region to region, 20 – 28 weeks, depending upon age of viability).

A woman who has never carried a pregnancy beyond 20 weeks is nulliparous and is called a nullipara or para 0. [6] A woman who has given birth once is primiparous and is referred to as a primipara or primip. A woman who has given birth two, three, or four times is multiparous and is called a multip. Grand multipara describes the condition of having given birth five or more times. [7]

Like gravidity, parity may also be counted. A woman who has given birth one or more times can also be referred to as para 1, para 2, para 3, and so on.

Viable gestational age varies from region to region.

In agriculture, parity is a factor in productivity in domestic animals kept for milk production. Animals that have given birth once are described as "primiparous" those that have given birth more than once are described as "pluriparous". [8] [9] Those that have given birth twice may also be described as "secondiparous", in which case "pluriparous" is applied to those that have given birth three times or more.

Nulliparity Edit

A nulliparous ( / n ʌ l ˈ ɪ p ə r ə s / ) woman (a nullipara or para 0) has never given birth. It includes women who have experienced spontaneous miscarriages and induced abortions before the mid-point of pregnancy, but not women who have experienced pregnancy loss after 20 weeks.

Prolonged nulliparity ( / ˌ n ʌ l ɪ ˈ p ær ɪ t i / ) is a risk factor for breast cancer. For instance, a meta-analysis of 8 population-based studies in the Nordic countries found that never giving birth was associated with a 30% increase in the risk of breast cancer compared with women who have given birth, and for every 2 births, the risk was reduced by about 16%. Women having their first birth after the age of 35 years had a 40% increased risk compared to those with a first birth before the age of 20 years. [10]

A number of systems are incorporated into a woman's obstetric history to record the number of past pregnancies and pregnancies carried to viable age. These include:

  • The gravida/para/abortus (GPA) system, or sometimes just gravida/para (GP), is one such shorthand. [citation needed] For example, the obstetric history of a woman who has had two pregnancies (both of which resulted in live births) would be noted as G2P2. The obstetric history of a woman who has had four pregnancies, one of which was a miscarriage before 20 weeks, would be noted in the GPA system as G4P3A1 and in the GP system as G4P3. The obstetric history of a woman who has had one pregnancy of twins with successful outcomes would be noted as G1P1+1. [11]
  • TPAL is one of the methods to provide a quick overview of a person's obstetric history. [12] In TPAL, the T refers to term births (after 37 weeks' gestation), the P refers to premature births, the A refers to abortions, and the L refers to living children. [13] When reported, the "abortions" number refers to the total number of spontaneous or induced abortions and miscarriages, including ectopic pregnancies, prior to 20 weeks. If a fetus is aborted after 20 weeks, spontaneously or electively, then it is counted as a premature birth and P will increase but L will not. [citation needed] The TPAL is described by numbers separated by hyphens. Multiple births (twins, triplets and higher multiples) count as one pregnancy (gravidity) and as one birth. For example, a pregnant woman who carried one pregnancy to term with a surviving infant carried one pregnancy to 35 weeks with surviving twins carried one pregnancy to 9 weeks as an ectopic (tubal) pregnancy and has three living children would have a TPAL annotation of T1, P1, A1, L3. This could also be written as 1-1-1-3.
  • The term GTPAL is used when the TPAL is prefixed with gravidity, and GTPALM when GTPAL is followed by number of multiple pregnancies. [13] For example, the gravidity and parity of a woman who has given birth at term once and has had one miscarriage at 12 weeks would be recorded as G2 T1 P0 A1 L1. This notation is not standardized and can lead to misinterpretations. [6]

Though similar, GPA should not be confused with the TPAL system, the latter of which may be used to provide information about the number of miscarriages, preterm births, and live births by dropping the "A" from "GPA" and including four separate numbers after the "P", as in G5P3114. This TPAL form indicates five pregnancies, with three term births, one preterm birth, one induced abortion or miscarriage, and four living children. [14]

In obstetrics, the term can lead to some ambiguity for events occurring between 20 and 24 weeks, [15] and for multiple pregnancies. [16]


Fertility facts

Extend Fertility, LLC provides management and support services to Extend Fertility Medical Practice. Extend Fertility Medical Practice is an independently owned professional corporation. All medical services, such as medication monitoring and egg retrieval, are directed and rendered solely by Extend Fertility Medical Practice. References on our website to the healthcare team refers to the physicians and nurses employed or contracted by Extend Fertility Medical Practice to provide health care services.

In addition to providing the services set forth above, Extend Fertility, LLC holds a tissue processing facility licenses, employs the embryologists, and performs certain services associated with egg freezing.


Labor is the physical efforts of expulsion of the fetus and the placenta from the uterus during birth (parturition). Toward the end of the third trimester, estrogen causes receptors on the uterine wall to develop and bind the hormone oxytocin. At this time, the baby reorients, facing forward and down with the back or crown of the head engaging the cervix (uterine opening). This causes the cervix to stretch and nerve impulses are sent to the hypothalamus, which signals for the release of oxytocin from the posterior pituitary. The oxytocin causes the smooth muscle in the uterine wall to contract. At the same time, the placenta releases prostaglandins into the uterus, increasing the contractions. A positive feedback relay occurs between the uterus, hypothalamus, and the posterior pituitary to assure an adequate supply of oxytocin. As more smooth muscle cells are recruited, the contractions increase in intensity and force.

There are three stages to labor. During stage one, the cervix thins and dilates. This is necessary for the baby and placenta to be expelled during birth. The cervix will eventually dilate to about 10 cm. During stage two, the baby is expelled from the uterus. The uterus contracts and the mother pushes as she compresses her abdominal muscles to aid the delivery. The last stage is the passage of the placenta after the baby has been born and the organ has completely disengaged from the uterine wall. If labor should stop before stage two is reached, synthetic oxytocin, known as Pitocin, can be administered to restart and maintain labor.


Watch the video: mom gave birth to our baby in the car! real footage (August 2022).