For most babies, birth occurs between 37 and 42 weeks. Due dates are calculated as 40 weeks after the woman's last menstrual period. Babies are considered post term when they are born after 42 weeks gestation, and 10 percent of pregnancies go post term, explains Dr. Errol R. Norwitz. Babies who are born post term appear different physically than babies born on time.
Thin Appearance
When a pregnancy goes post term, the placenta ages and fails to provide adequate nutrition to the unborn baby. The Merck Manual explains that post term infants have less subcutaneous fat stored due to the lack of nutrients. At birth, these babies are thin and the skin appears loose and wrinkly because of the weight loss.
Increased Weight
The longer a baby stays in utero, the more weight he gains. Dr. Norwitz explains that post term babies can weigh in excess of 10 pounds at birth. Because of the extra weight, doctors often give women the option of a cesarean section to prevent complications of delivering a large baby.
Dry Skin
Prolonged exposure to amniotic fluid after the protective layer of vernix wears off can cause a post term baby's skin to dry out. In some cases, the Merck Manual notes that the skin will begin to peel.
Meconium Staining
Post term babies have an increased risk of passing a bowel movement in utero, also known as meconium. When the meconium mixes with the amniotic fluid, the baby may experience meconium staining especially to the fingernails and umbilical cord, leaving a greenish tint.
Hair and Nails
Hair and nails continue to grow during pregnancy. When born, post term babies will have longer fingernails as well as more hair than other babies born between 37 and 42 weeks.
