8. Fertility, Pregnancy, and Childbirth. Pregnancy Is Confirmed by Hormonal Tests. After implanting into the endometrium, embryos begin to secrete hCG—a hormone that is detected by pregnancy tests.
8 Fertility, Pregnancy, and Childbirth
Pregnancy Is Confirmed by Hormonal Tests • After implanting into the endometrium, embryos begin to secrete hCG—a hormone that is detected by pregnancy tests. • Laboratory tests for pregnancy are very accurate, but they must be ordered by a health care provider. • Home pregnancy tests are convenient and popular, but the results from these tests are less accurate than laboratory tests. • Definitive clinical evidence of pregnancy can be obtained at 5 to 6 weeks by ultrasound.
The Likelihood of Achieving Pregnancy Can Be Maximized by Tracking Ovulation • For fertile couples who engage in sex without contraception several times a week, there is a 93% chance of pregnancy within one year. • If a woman does not become pregnant after one year of sex with no contraception, the couple is considered subfertile. • To increase the chance of becoming pregnant, couples should time intercourse to occur during the “fertile window.”
Figure 8.2 The likelihood of conception depends on when coitus occurs with respect to the day of ovulation
Infertility Can Result from Problems in the Woman or in the Man • Subfertility and infertility are common. • Many factors reduce sperm counts in men. • Undescended testes, sex chromosome anomalies, infections, chemotherapy, environmental toxins, and tight clothing can all lead to insufficient or poor-quality sperm. • In artificial insemination, sperm are placed directly into the woman’s vagina and uterus. This technique can be used to bring about pregnancy for couples in which the man has poor sperm quality.
Infertility Can Result from Problems in the Woman or in the Man • In vitro fertilization—or the mixing of sperm with ova in a Petri dish—circumvents many problems with sperm. • Half a million babies have been born in the United States with the help of assisted reproductive technologies. • Babies conceived with such technologies have two to three times the risk of prematurity, low birth weight, and infant mortality compared with babies conceived without such technology.
Infertility Can Result from Problems in the Woman or in the Man • Sperm can be donated to sperm banks to assist with pregnancy. • Abnormalities of the female reproductive tract also contribute to sub- and infertility. • Failure to ovulate can be ameliorated with drugs or egg donation.
Infertility Can Result from Problems in the Woman or in the Man • For women who cannot sustain pregnancies at all, some couples opt to use surrogates. • Adoption is limited by the supply of healthy infants. • Fertility declines with age. • Children born to older parents stand a greater risk of chromosomal abnormalities such as Down syndrome.
Many Embryos Do Not Survive • Approximately 50% of all human embryos are genetically abnormal and have little or no chance of giving rise to a viable child. • Rh factor incompatibility can threaten later pregnancies. • Ectopic pregnancies can endanger a woman’s life.
Figure 8.9 Ectopic pregnancy can occur in the oviduct, on the ovary or cervix, or elsewhere
Pregnancy Is Conventionally Divided into Three Trimesters • During the first trimester the embryo implants in the uterine wall and establishes a system of hormonal and metabolic communication with the mother. • During the first trimester the fetus possesses all organ systems and has developed male or female genitalia. • Adequate nutrition is vital to a successful pregnancy. • Substances, organisms, and physical agents can harm a fetus.
The Second Trimester Is the Easiest • The second trimester begins at 13 weeks of gestational age and is usually the easiest for the woman. Tests can detect fetal abnormalities at this time. • Quickening begins during the second trimester.
The Second Trimester Is the Easiest • Sex during pregnancy is healthy, although sexual activity generally decreases during this time. • Moderate exercise during pregnancy is beneficial.
Figure 8.15 Sex during the later stages of pregnancy may be facilitated by a willingness to try new positions or sexual activities other than coitus
The Third Trimester Is a Time of Preparation • A hospital is the best location for childbirth if problems are foreseen. • Childbirth classes prepare parents for birth. • The fetus also prepares for birth.
Labor Has Three Stages • The first stage of labor consists of uterine contractions that open the cervix. • The second stage is delivery of the baby, aided by uterine contractions and bearing down. • Premature births occur in 10% of pregnancies in the United States. • 75% of neonatal deaths occur in babies born prematurely. • Delayed births occur in 10% of pregnancies in the United States. • Post-term babies are three times more likely to die neonatally than babies born at term. • The third stage is delivery of the placenta.
Labor Has Three Stages • Cesarean section (C-section) is delivery of the baby through an incision in the abdomen. • In the United States, almost 1 in 3 hospital births is by C-section.
The Period after Birth Places Many Demands on Parents • The weeks following birth are called the postpartum. • Some women experience postpartum depression or depressive psychosis. • Childbirth and parenting can decrease sexual activity. • If all is well, couples can initiate intercourse 3 to 6 weeks following delivery.
Breast-Feeding Is the Preferred Method of Nourishing the Infant • Lactation is influenced by the hormones prolactin and oxytocin. • Over the first 2 weeks following birth, breast milk composition changes. • Breast feeding has many advantages and some disadvantages. • Infant formula is an alternative to breast milk.