The second trimester includes the second 15 weeks of pregnancy (weeks 14 to 28). The fetus looks noticeably more human.
Prenatal Development The fetus grows dramatically during the second trimester and by the end of the trimester is 13 inches long. He or she has developed tooth buds and reflexes, such as sucking and swallowing. Though the gender of the fetus is determined at conception, it is not immediately apparent during development. If the baby is positioned correctly during ultrasound, gender may be determined as early as 16 weeks, although most of the time it is not possible until 20 to 22 weeks.
During the second trimester, the mother will often feel the fetus moving around inside her uterus. Soft hair, called lanugo (lan-NEW-go), and a waxy substance, known as vemix, both cover the fetus’s body. These may develop to protect the fetus from the constant exposure to the amniotic fluid. By the end of the second trimester, the fetus will weigh about 13/4 pounds. If birth takes place at the end of the second trimester, the baby may be able to survive with intensive medical care. We discuss premature birth later in this chapter.
Changes in the Pregnant Mother During the second trimester, nausea begins to subside as the body adjusts to the increased hormonal levels. Breast sensitivity also tends to decrease. However, fatigue may continue, as well as an increase in appetite, heartburn, edema (ankle or leg swelling), and a noticeable vaginal discharge. Skin pigmentation changes can occur on the face. As the uterus grows larger and the blood circulation slows down, constipation and muscle cramps bother some women. Internally, the cervix turns a deep red, almost violet color, due to an increased blood supply.
As the pregnancy progresses, the increasing size of the uterus and the restriction of the pelvic veins can cause more swelling of the ankles. Increased problems with varicose veins and hemorrhoids may also occur. Fetal movement is often felt in the second trimester, sometimes as early as the 16th week. Usually women can feel movement earlier in their second or subsequent pregnancies because they know what fetal movement feels like.
The second trimester of pregnancy is usually the most positive time for the mother. The early physiological signs of pregnancy such as morning sickness and fatigue lessen, and the mother-to-be finally feels better physically. This improvement in physical health also leads to positive psychological feelings including excitement, happiness, and a sense of well-being. Many women report an increased sex drive during the second trimester, and for many couples, it is a period of high sexual satisfaction.
As the developing fetus begins to move around, many women feel reassured after anxiously wondering whether the fetus was developing at all. In fact, many women report that the kicking and moving about of the developing fetus is very comforting. Finally, the transition to maternity clothes often results in more positive feelings, probably because it is now obvious and public knowledge that the woman is pregnant.
Prenatal Development By the end of the 7th month, the fetus begins to develop fat deposits. She or he can react to pain, light, and sounds. Some fetuses develop occasional hiccups or begin to suck their thumb. If a baby is born at the end of the 7th month, there is a good chance of survival. In the 8th month, the majority of the organ systems are well developed, although the brain continues to grow. By the end of the 8th month, the fetus is 15 inches long and weighs about 3 pounds. During the third trimester, there is often stronger and more frequent fetal movement, which will slow down toward the 9th month (because the fetus will have less room to move around). At birth, an infant on average weighs 71/) pounds and is 20 inches long.