Postterm Pregnancy

Although there is no way to conclusively determine whether a woman’s pregnancy will extend beyond the normal gestation period, there are certain risk factors that make it more likely. These factors include (1, 2):

• A prior postterm pregnancy
• A first pregnancy for the mother
• A male fetus
• Genetic factors
• Obesity
• Older maternal age
• The baby’s mother or father was born postterm
• Mother of caucasian, non-hispanic ethnicity

It is essential that medical professionals recognize these risk factors and consider the possibility of postterm pregnancy during prenatal care.

As a pregnancy continues past 40 weeks, the risk of harm to the baby increases. Many of the complications associated with postterm pregnancy are due to placental insufficiency. As a pregnancy nears term the placenta begins to deteriorate. Because the placenta is the baby’s source of oxygen-rich blood, this deterioration poses a serious risk to the growing fetus (1, 2). Because the baby continues to grow as the pregnancy passes 40 weeks, many other complications of postterm pregnancy are due to large fetal size (1, 2).

The following are common fetal/neonatal complications of postterm pregnancy (1, 2):

• Prolonged labor
• Birth trauma
• Increased incidence of mechanical delivery (i.e. use of forceps and/or vacuum extractors)
• Shoulder dystocia
• Meconium aspiration
• Oligohydramnios
• Umbilical cord compression
• Fetal distress
• Persistent pulmonary hypertension
• Birth asphyxia
• Infection
• Intrauterine growth restriction (IUGR)

If these complications are mismanaged or go untreated, they can lead to severe consequences and/or lifelong disabilities for the baby. The following are common injuries and complications that come as a result of mismanaged postterm pregnancy (1, 2):

• Stillbirth or neonatal death
• Postmaturity/dysmaturity syndrome: A condition that results from chronic intrauterine malnutrition due to insufficient placental conditions. Babies born with postmaturity syndrome often have long thin bodies, long nails, have dry skin, and are small for gestational age.
• Hypoglycemia
• Cerebral palsy
• Hypoxic-ischemic encephalopathy (HIE)
• Seizures

In addition to the many risks to the baby associated with postterm pregnancy, mothers also face a series of potential complications. The following are common maternal complications associated with postterm pregnancy (1, 2):

• Postpartum hemorrhage (excessive bleeding following the birth of a baby)
• Cervical rupture (torn cervix due to the large size of the baby)
• Infection
• Perineal injury (injury to the labia, vagina, and/or rectum)
• Labor dystocia
• Endometritis (inflammation of the endometrial lining of the uterus)

Because of the serious risk to both the mother and baby associated with postterm pregnancy, it is essential that medical professionals do everything they can to prevent this condition. There are two major strategies used to prevent postterm pregnancy:

Increased prenatal testing near due date

If a mother has still not delivered by about the 39th or 40th week of pregnancy, the obstetrician will likely order weekly or twice-weekly tests to check on the well-being of the baby (1, 2). Typically these include special fetal monitoring tests like a non-stress test (a test that measures the baby’s movement, heart rate, and reactivity of heart rate to movement, and can indicate if the baby is not receiving enough oxygen due to placental or umbilical cord problems) and biophysical profile (measures the baby’s heart rate, muscle tone, movement, breathing, and the amount of amniotic fluid present). Additionally, ultrasounds should be performed to evaluate the amount of amniotic fluid around the baby (1, 2).

Labor induction by 40-41 weeks gestation

Reports and medical literature state that for even uncomplicated, single baby pregnancies it is best to induce labor by about the 40th or 41st week (1, 2). Similarly, most obstetricians recommend delivery by 41 weeks. Medical professionals must weigh the risks and benefits of labor induction and ensure that the mother and baby are optimal candidates for induction. The benefits of labor induction include reduced C-section rates, lower rates of meconium-stained fluid, less fetal heart abnormalities, reduced oxygen deprivation problems, and much more (1, 2). Unless the mother and baby will be put at serious risk by pursuing labor induction, there is virtually no benefit to prolonging pregnancy beyond 40 weeks and, in fact, strong scientific evidence has shown that any pregnancy beyond 40 weeks of gestation puts the baby and mother at increased risk for health problems (1, 2).