Summary

1. The first two weeks of prenatal growth are called the germinal period. During this time, the single-celled zygote multiplies into more than 100 cells that will eventually form both the placenta and the embryo. The growing organism travels down the fallopian tube to implant in the uterus.
2. From the third through the eighth week after conception is the embryonic period. The heart begins to beat, and the eyes, ears, nose, and mouth form. By the eighth week, the embryo has the basic organs and features of a human, with the exception of the sex organs.
3. The fetal period extends from the ninth week until birth. In the ninth week, the sexual organs develop. By the end of the third month, all the organs and body structures have formed. The fetus attains viability at 22 weeks, when the brain can regulate basic body functions. Babies born before the 26th week are at high risk of death or disability.
4. The average fetus gains approximately 5 pounds (2,268 grams) from the 6^th to the 9^th month, weighing 7 1/2 pounds (3,400 grams) at birth. Maturation of brain, lungs, and heart ensures survival of more than 99 percent of all full-term babies born in developed nations.

5. Birth typically begins with contractions that push the fetus out of the uterus and then through the vagina. The Apgar scale, which rates the newborn at one minute and again at five minutes after birth, provides a quick evaluation of the infant’s health.
6. Medical assistance can speed contractions, dull pain, and save lives. However, many aspects of medicalized birth have been criticized as impersonal and unnecessary, including about half the cesareans performed in the United States. Contemporary birthing practices are aimed at finding a balance and protecting the baby, but also allowing more parental involvement and control.

7. Some teratogens (diseases, drugs, and pollutants) cause physical impairment. Others, called behavioral teratogens, harm the brain and therefore impair cognitive abilities and affect personality.
8. Whether a teratogen harms an embryo or fetus depends on timing, dose, and genes. Public and personal health practices can protect against prenatal complications, with some specifics debatable. Always, however, family members affect the pregnant woman’s health.
9. Low birthweight (under 5½ pounds, or 2,500 grams) may arise from multiple births, placental problems, maternal illness, malnutrition, smoking, drinking, illicit drug use, and age. Compared with full-term newborns, preterm and underweight babies experience more medical difficulties and psychological problems for many years. Babies that are small for gestational age (SGA) are especially vulnerable.
10. Birth complications, such as unusually long and stressful labor that includes anoxia (a lack of oxygen to the fetus), have many causes. Long-term handicaps are not inevitable for high-risk children, but careful nurturing from their parents and society may be needed.

11. Humans are social animals, from the moment of birth. The Brazelton Neonatal Behavioral Assessment Scale measures 46 newborn behaviors, 20 of which are reflexes.
12. Fathers can be supportive during pregnancy as well as helpful in birth. Paternal support correlates with shorter labor and fewer complications. Some fathers become so involved with the pregnancy and birth that they experience couvade.
13. Many women feel unhappy, incompetent, or unwell after giving birth. Postpartum depression gradually disappears with appropriate help; fathers may be crucial for mother and child. Ideally, a parental alliance forms to help the child develop well.
14. Kangaroo care benefits all babies but especially those who are vulnerable. Mother–newborn interaction should be encouraged, although the parent–infant bond depends on many factors in addition to birth practices.