Diseases & Conditions
A postmature newborn is a newborn delivered after more than 42 weeks in the uterus.
Postmature (postterm) delivery is much less common than premature (preterm) delivery. The reason for a pregnancy to continue beyond term is usually unknown.
Reduced function of the placenta is the greatest risk to fetuses who go beyond term. Near the end of a term pregnancy, the placenta begins to shrink. As it shrinks, the placenta becomes less able to provide adequate nutrients to the fetus. To compensate, the fetus begins to use its own fat and carbohydrates to provide energy. As a result, its growth rate slows, and occasionally its weight may decrease. If the placenta shrinks sufficiently, it may not provide adequate oxygen to the fetus, particularly during labor. A lack of adequate oxygen may result in fetal distress (see Labor and Delivery Complications: Fetal Distress ) and, in extreme cases, may result in injury to the fetal brain and other organs. Fetal distress may cause the fetus to pass stools (meconium) into the amniotic fluid. The fetus may also take deep, gasping breaths triggered by the distress and thereby inhale the meconium-containing amniotic fluid into the lungs before or during birth. As a result, the newborn may have difficulty breathing after delivery (meconium aspiration syndrome).
A postmature newborn has dry, peeling, loose skin and may appear emaciated, especially if the function of the placenta was severely reduced. The newborn often appears alert. The skin and nail beds may be stained green if meconium was present in the amniotic fluid. A postmature newborn is prone to developing low blood sugar levels (hypoglycemia) after delivery, especially if oxygen levels were low during labor.
The postmature newborn who experienced low oxygen levels and fetal distress may need resuscitation at birth. If meconium has been breathed into the lungs, a ventilator may be needed. Intravenous glucose solutions or frequent breast milk or formula feedings are given to prevent hypoglycemia.
If these problems do not occur, the major goal is to provide good nutrition so that the newborn can catch up to the weight that is appropriate for him.
Last full review/revision February 2003
Source: The Merck Manual Home Edition