Prenatal Development

The fetal stage begins in the ninth week of pregnancy and continues until the birth of the baby, usually about thirty weeks later.

The thrill of the first-time mother feeling the movements of the fetus in the fourth or fifth month of pregnancy is unforgettable. By this time, the fetus can open and close its mouth, swallow, and make certain head movements. It may even suck its thumb. The fastest growth period for the fetus is the fourth month, when it almost doubles in length, reaching six inches (15.2 centimeters) from crown to rump. Limbs become sensitive to touch, and a heartbeat can be heard with a stethoscope, a thrilling and sometimes mystifying experience for parents-to-be.

The fetus is becoming more of an individual during this stage. Some fetuses move around a great deal while others are relatively quiet. The fetus' sense of hearing has also begun to function during this period, as evidenced by startled reactions to loud sounds.

After five months the skin of the fetus is fully developed. Hair, nails, and sweat glands are apparent, and the fetus even sleeps and wakes and keeps almost regular hours. In month six the eyelids can open, and the fetus can open and close its eyes. It may now weigh as much as twenty-four ounces (680 grams). During month seven the eyes can distinguish light from dark, and the brain has more control over body systems than before. The most important aspect of this particular time in development is that an infant born prematurely now has a fair chance for survival. In the last two months the fetus gains about eight ounces (227 grams) per week and gets ready for birth.