A condition in which a pregnancy persists for longer than 42 weeks; the average length of a normal pregnancy is 40 weeks (see gestation). Postmaturity may be associated with a family tendency to prolonged pregnancy, or it may be a sign that the baby is unable to descend properly (see engagement). The risk of fetal death increases after 42 weeks because the placenta becomes less efficient. Postmature infants tend to have dry skin and may be more susceptible to infection.