Postterm Pregnancy and Birth Injury

Postterm pregnancy (also known as postdate pregnancies, prolonged pregnancies, and postmaturity) is a name for pregnancies that extend beyond the standard gestation time (approximately 40 weeks). In cases of postterm pregnancy, the baby may become over-developed and too large, and delivery may be difficult, increasing the risk for birth trauma, brain bleeding, hypoxic-ischemic encephalopathy (HIE), cerebral palsy, seizures and brain damage. Postterm pregnancies also pose a health risk to the baby because placental function and size begin to deteriorate after 37 weeks. The longer the pregnancy, the more the placenta begins to deteriorate, placing the baby at risk of fetal oxygen deprivation or nutrient exchange losses. Because of these serious health risks, there is a consensus that it is best to induce labor between 40-41 weeks or sooner rather than letting it continue further.

Postterm Pregnancy

What Is Postterm Pregnancy?

Most pregnant women (about 80%) give birth between 37 and 42 weeks. About 10% give birth before 37 weeks and the remaining 10% extend until after the end of the 42nd week. When a pregnancy goes beyond the normal gestation time it is called a “postterm pregnancy” or “post due date pregnancy” and can be very dangerous for the baby.  In general, the longer a pregnancy continues after 40 weeks, the more risks there are to the baby. Research strongly suggests that due to the increase in fetal death and injury at 42 weeks and beyond, it is much safer to induce labor by about 40 or 41 weeks than to allow the pregnancy to continue.

The longer a pregnancy continues after 40 weeks, the more risks there are. The major risk comes from the fact that the placenta reaches its maximum size and surface area around 37 weeks. After this time, the surface area and function gradually deteriorate, which can cause placental insufficiency. This is very serious because the placenta is an organ that attaches to the inside of the uterus (womb) and helps bring oxygen-rich blood to the baby. If the placenta stops functioning, as in the case of complete placental abruption, for example, the baby would be completely deprived of oxygen. In addition to oxygen and other gas transport, the placenta helps bring nutrients to the baby. If the baby doesn’t receive sufficient oxygen, she can become hypoxic, which means her cells and tissues aren’t receiving sufficient oxygen. Hypoxia and malnutrition can cause organ damage, including brain damage.

In addition to placental insufficiency, going past the due date increases the risk of intrauterine infection, macrosomia, umbilical cord compression due to oligohydramnios, and meconium aspiration. All these conditions increase a baby’s risk of hypoxia and brain damage. Umbilical cord compression is an obstetrical emergency because it can cause the baby to be severely – even completely – cut off from her supply of oxygen-rich blood.

In addition to being hypoxic, a postterm baby may also be malnourished and may suffer from dysmaturity syndrome, which is a term used to describe babies who have characteristics of IUGR caused by placental insufficiency. These babies are at risk of complications such as umbilical cord compression, nonreassuring heart tracings, meconium aspiration, neonatal hypoglycemia,  and respiratory insufficiency.

Postterm Pregnancy Can Cause Birth Injuries Such As Hypoxic Ischemic Encephalopathy (HIE)

There are numerous problems that may occur to both the baby and the mother if a pregnancy is allowed to continue beyond the normal gestation period. While some are minor and resolve on their own, others are more serious and result in irreversible and lifelong disabilities for the child. These include:

  • Postmaturity syndrome. Occurring in roughly 20% of post-date pregnancies, this syndrome develops due to uteroplacental insufficiency which causes chronic stress and hypoxia (oxygen deprivation) in the baby. The baby has a unique appearance when born including overgrown fingernails and hair, a long body with little fat, and wrinkled or dry, parchment-like skin. Postmaturity syndrome features a number of disorders:
  • Uteroplacental insufficiency. The major risk to a baby comes from the fact that the placenta reaches its maximum size and surface area around 37 weeks. After 37 weeks, its surface area and function gradually deteriorate. This may mean that the placenta is less able to supply sufficient blood and oxygen to the baby. When the placenta is unable to supply sufficient oxygen, it poses an increased risk for hypoxic-ischemic encephalopathy (HIE). Numerous birth injuries are associated with HIE including cerebral palsy, intellectual disabilities and seizures.
  • Fetal Distress/Nonreassuring Fetal Assessment During labor and delivery, a fetal monitor will assess a baby’s heart rate along with the mother’s contractions. If a baby is not responding well and is not being adequately oxygenated during delivery, fetal monitoring will be nonreassuring, indicating fetal distress. In postterm pregnancies, there is increased risk of fetal distress due to the higher incidence of cord compression.
  • Meconium aspiration Sometimes fetal stress and an older gestational age may induce a bowel movement by the baby while in the uterus. Meconium staining  (the infant’s skin, umbilical cord, or nailbeds are stained green or yellow) may occur. This generally resolves on its own in time. However, in some cases, the baby will actually inhale the tainted amniotic fluid into its lungs. This may cause irritation, airway obstruction, infection, problems with normal lung expansion, HIE, and potential brain damage.
  • Oligohydramnios. Amniotic fluid is a clear, yellowish liquid which surrounds the baby in the amniotic sac during pregnancy. At first, the fluid consists of water and then around 20 weeks fetal urine becomes the primary substance. The baby breathes and swallows amniotic fluid which aids in lung maturation, growth, and maintaining a consistent temperature. The volume of amniotic fluid increases during pregnancy and reaches its peak at around 34 weeks. When there is an unexpected decrease in the amount of amniotic fluid, it is called oligohydramnios. This condition occurs in about 12% of postterm pregnancies with a large 25% decrease in fluid levels occurring each week beyond about 41 weeks. Oligohydramnios can cause cord compression and other ominous pregnancy outcomes.
  • Umbilical cord compression. When oligohydramnios occurs, there is a serious risk of cord compression. This is because the baby and umbilical cord no longer float in the fluid. Instead, the baby’s movements can put direct pressure on the cord cutting off oxygen, blood, and nutrients.
  • Macrosomia. A baby can become very large when a pregnancy is postterm. This makes it more difficult to deliver vaginally. This may prompt a physician to use forceps or a vacuum extractor for delivery assistance, which may increase the likelihood of birth trauma to the baby. Macrosomia also increases the chances for C-section when labor becomes prolonged due to problems like shoulder dystocia (the baby’s shoulder is obstructed and cannot be delivered normally) or cephalopelvic disproportion (the baby’s head becomes too large to fit through the mother’s pelvis). In fact, Cesarean delivery is twice as likely in a postterm pregnancy.
  • Stillbirth. This is the devastating event where a baby dies before birth. The risk of stillbirth increases with every week that a pregnancy extends beyond the typical 40 week gestation period.

Other Risks of a Postterm Pregnancy for a Baby

Babies continue to grow from weeks 39 – 43. When a baby is large, the baby is at risk of experiencing trauma during delivery as well as umbilical cord compression. Macrosomia attributed to a post-term pregnancy increases the risk of:

Maternal Risks of Postterm Pregnancy

  • Postpartum hemorrhage (excessive bleeding following the birth of a baby)
  • Cervical rupture (torn cervix due to the large size of the baby)
  • Infection, like chorioamnionitis (infection of fetal membranes due to a bacterial infection that ascends from the vagina resulting from a prolonged labor).
  • Perineal injury due to the large size of the baby.
  • Labor dystocia
  • Endometritis

Predicting Postterm Pregnancy

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

  • A prior postterm pregnancy
  • A first pregnancy for the mother
  • A male fetus
  • Genetic factors
  • Obesity

Preventing Postterm Pregnancy: Increasing 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. Typically these include special fetal monitoring tests like a non-stress test (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.

Preventing Postterm Pregnancy: Labor Induction by 40-41 Weeks

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. Similarly, most obstetricians recommend delivery by 41 weeks. The benefits of labor induction are many and include reduced C-section rates, lower rates of meconium-stained fluid, less fetal heart abnormalities, reduced oxygen deprivation problems, and much more. 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.

Pregnant women beyond their due date should be proactive about delivery. Mothers need to insist that the physician or midwife induces labor or schedules a C-section before 41 weeks. The baby and mother’s health may otherwise be at risk.

Legal Help for Postterm Pregnancy Injuries

Trusted Birth Trauma and HIE Attorneys

If you or a loved one were injured as the result of a mishandled post-term pregnancy, call the award-winning birth injury attorneys at Reiter & Walsh ABC Law Centers. With over 100 years of joint legal experience, our legal team has the education, qualifications, results, and accomplishments necessary to succeed. We’ve handled cases involving dozens of different complications, injuries, and instances of medical malpractice related to obstetrics and neonatal care. While our office is based in Detroit, Michigan, our team is able to handle cases from all over the country. We’ve helped clients and their families in Michigan, Ohio, Arkansas, Mississippi, Tennessee, Texas, Wisconsin, Pennsylvania, Washington D.C., and other parts of the United States.

To begin your free birth injury case evaluation, contact us in any of the following ways. We’re available to speak with you 24/7.

Free Case Review | Available 24/7 | No Fee Until We Win

Phone (toll-free): 888-419-2229
Press the Live Chat button on your browser
Complete Our Online Contact Form

Video: Hypoxic Ischemic Encephalopathy (HIE; Birth Asphyxia)

Watch a video of hypoxic-ischemic encephalopathy lawyers Jesse Reiter and Rebecca Walsh discussing the causes of birth asphyxia.


  • Clinical Practice Obstetrics Committee, Maternal Fetal Medicine Committee, Delaney M, et al. Guidelines for the management of pregnancy at 41+0 to 42+0 weeks. J Obstet Gynaecol Can 2008; 30:800.
  • Kramer MS, McLean FH, Boyd ME, Usher RH. The validity of gestational age estimation by menstrual dating in term, preterm, and postterm gestations. JAMA 1988; 260:3306.
  • Bennett KA, Crane JM, O’shea P, et al. First trimester ultrasound screening is effective in reducing postterm labor induction rates: a randomized controlled trial. Am J Obstet Gynecol 2004; 190:1077.
  • Denison FC, Price J, Graham C, et al. Maternal obesity, length of gestation, risk of postdates pregnancy and spontaneous onset of labour at term. BJOG 2008; 115:720.
  • Knox GE, Huddleston JF, Flowers CE Jr. Management of prolonged pregnancy: results of a prospective randomized trial. Am J Obstet Gynecol 1979; 134:376.
  • Yeh SY, Read JA. Management of post-term pregnancy in a large obstetric population. Obstet Gynecol 1982; 60:282.
  • Lagrew DC, Freeman RK. Management of postdate pregnancy. Am J Obstet Gynecol 1986; 154:8.