Fetal development at 15 weeks pregnant includes significant changes to the baby's appearance and behavior. While the mother-to-be may just be beginning to show signs of a baby bump, inside her belly the fetus is hard at work completing the development of his major organs and bodily systems.
Growth
At the 15th week of pregnancy, the developing fetus is about 4 3/4 inches long. The baby weighs about 2 ounces. His body is becoming more recognizable as a baby now, with head and limbs reaching proportional lengths to the rest of the body. The legs have grown enough to be longer than the arms by 15 weeks.
Appearance
At 15 weeks gestation, a baby has thin, translucent skin. Blood vessels can be spotted through the skin. The features of his face are still developing, but are beginning to take on a recognizable appearance. The eyes are moving from the sides of the face to their future forward position. Eyebrows and eyelashes have begun to grow in and he has some hair growing on his head by this point. There is also the beginnings of lanugo, the fine hair that will coat the baby's entire body during the next few months of pregnancy. The genital organs are formed now and may be recognizable on ultrasound at 15 weeks, allowing parents-to-be to learn the gender of their unborn child.
Senses
The senses are developing quickly now and the 15-week-old fetus can sense light from outside the womb. The taste buds are forming and he may be able to distinguish different tastes in the amniotic fluid, which change depending on what mom has been eating.
Internal Organs
Inside the body of the 15-week-old fetus, the skeleton has begun to harden, a process called ossification. His heartbeat is steady and his circulatory system mostly formed by this point. The digestive, urinary and respiratory tracts are also mostly complete and the baby has begun to swallow and suck in amniotic fluid into the stomach and lungs, helping him get ready for the activities of digestion and breathing after birth.
Behavior
In the 15th week of pregnancy, babies exhibit some recognizable behaviors. When viewed via ultrasound, a 15-week-old fetus often can be seen moving around within the amniotic sac, kicking his legs and moving his arms. He may grasp the umbilical cord or his own limbs. Some babies at this gestational age are spotted sucking their thumbs in the womb. Pregnant women might also start to feel fetal hiccups.
