The Birth Process

to 40 percent during the first trimester. The breasts grow in size and become tender. The uterus just becomes palpable above the pubic bone at 12 weeks’ gestation.

Women tend to be more energetic in the second trimester and the uterus can be seen above the pubic bone. In total, the uterus expands twenty times its normal size. Fetal movement is felt at about 20 weeks’ gestation or slightly earlier than that in subsequent pregnancies.

In the third trimester, most of the weight is gained and the fetus sits in the head-down position most of the time. There will be regular fetal movement, which can be disruptive. Eventually, the head engages and there is increased pressure on the bladder.

Prenatal care can begin before pregnancy with preconception counseling. Prenatal medical care is recommended throughout the pregnancy in order to monitor for pregnancy-related complications. Nutrition is important before and during pregnancy. Folic acid consumption is particularly important in order to prevent spina bifida in the fetus. Omega-3 fatty acids are also helpful in brain and eye development. Iron is important to prevent anemia. Calcium and vitamin D are important for bone development. Foods that should be avoided are those that are unwashed and might contain pathogens, and unpasteurized deli meats and dairy products.

Women need to gain weight in order to have a healthy baby. Overweight women do not need to gain as much as underweight women. About 25 to 35 pounds is recommended for the woman who has a normal body mass index prior to getting pregnancy. Gaining too much weight can increase the risk of a cesarean section, hypertension in pregnancy, and large fetal size. Regular aerobic exercise is recommended unless there are pregnancy complications.

THE BIRTH PROCESS

The birth process in humans is called childbirth. It is the final aspect of a pregnancy that involves expulsion of the fetus, which becomes an infant, from the vagina or through Cesarean section. Childbirth usually happens in a hospital in a developed country and in a home in developing countries.

There are four stages of labor. The first stage of labor involves cervical dilation and lasts about 12 to 19 hours. The second stage of labor is when the fetus or infant is delivered, which lasts about 1 to 2 hours. The third stage of labor is when the placenta is delivered, which lasts 5 to 20 minutes. The fourth stage of labor is the hour or so after the placenta is delivered, when bleeding is controlled and the woman’s episiotomy, if given, is repaired.

Labor starts with an increase in uterine contractions, which become strong and repetitive. The contractions also become more painful and some women receive opioid pain medications or what’s called an epidural block, which involves injecting an anesthetic into the epidural space around the lower spinal cord to anesthetize the pelvic and leg structures. As the head descends the birth canal or vagina, which stretches markedly, it is said to crown, when it is visible at the vaginal opening.

The hormone, oxytocin, is increased in late pregnancy, which increases contentment, calmness, and a sense of bonding with the partner. The uterus is also sensitive to this hormone, resulting in increased uterine contractions and expulsion of the fetus. Oxytocin after birth and during breastfeeding will increase bonding and maternal behavior after childbirth. It causes the letdown reflex in breastfeeding.

As many as 80 percent of mothers in the US will report sadness after delivery of their baby, often called the “baby blues”. This can last a few minutes to a few days and disappears after two weeks’ postpartum. About 10 percent of women will develop postpartum depression, which is more long-lasting and has a greater effect on infant bonding and the care of the infant.

Figure 24 shows the stages of labor in a vaginal delivery:

Figure 24.

The cervix ripens before delivery so that it is softer and easier to thin and dilate. In the first stage of labor, this will dilate to full cervical dilation status, often referred to as being 10 centimeters dilated. Most women start labor with uterine contractions, while some will have rupture of membranes, which is the breakage of the amniotic sac around the baby. The first stage of labor is sometimes divided into a latent stage and active stage, the later allowing for greater contractions and more cervical dilation.

In the second stage of labor, the fetus is delivered. There is marked stretching of the perineum, which is the space between the vaginal introitus and the anus. This is the area that is cut if an episiotomy is done. This stage can be short in women who’ve given birth before but requires a longer period of stretching if the woman has never given birth. Head and shoulders are the hardest part to deliver, with the shoulders sometimes becoming stuck. The remainder of the infant’s body is relatively easy to slip out of the vagina.

The third stage of labor can be just a few minutes or up to 20 or more minutes. There is a gush of blood as the placenta separates and before it can be expelled from the vagina.