A postmature newborn is delivered after more than 42 weeks in the uterus.
Postmature (postterm) delivery is much less common than premature (preterm) delivery. Why a pregnancy continues beyond term is usually unknown.
Reduced function of the placenta (the organ that connects the fetus to the uterus and provides nourishment to the fetus) is the greatest risk to fetuses who go beyond term. Near the end of a term pregnancy, the placenta becomes smaller and less effective in providing oxygen and nutrients to the fetus. To compensate, the fetus begins to use its own fat and carbohydrates (sugars) to provide energy. As a result, its growth rate slows, and occasionally weight may even decrease. Postmature newborns are prone to developing low blood sugar levels (hypoglycemia) after delivery because they have exhausted their supply of stored fat and carbohydrates. 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 Complications of Labor and Delivery: Fetal Distress) and, in extreme cases, may result in injury to the brain and other organs. Fetal distress may cause the fetus to pass stools (meconium) into the amniotic fluid. The fetus may also reflexively take deep, gasping breaths triggered by the distress and thereby inhale the meconium-containing amniotic fluid into the lungs before birth. As a result, the newborn may have difficulty breathing after delivery (meconium aspiration syndrome—see Problems in Newborns: Meconium Aspiration Syndrome).
Postmature newborns have dry, peeling, loose skin and may appear emaciated, especially if the function of the placenta was severely reduced. The fingernails and toenails are long. The umbilical cord and nails may be stained green if meconium was present in the amniotic fluid.
Postmature newborns who experience low oxygen levels and fetal distress may need resuscitation at birth. If meconium is present in the amniotic fluid and the newborn is lethargic, a tube is passed into the windpipe (trachea) to suction as much meconium as possible from the respiratory tract. If meconium has been breathed into the lungs, a ventilator may be needed to support breathing. Sugar (glucose) solutions given by vein (intravenously) 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 postmature newborns can catch up to the weight that is appropriate for them.
Last full review/revision February 2009 by Arthur E. Kopelman, MD