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Premature birth is often associated with a heightened risk of an infant developing medical issues, but delivering a baby past the due date can also lead to health problems, including the risk of cerebral palsy. Post-term late pregnancy increases the chances of macrosomia (a large baby), umbilical cord issues, and birth asphyxia, among other medical complications.
What Is Post Term Pregnancy?
According to the U.S. National Institutes of Health, post-term pregnancy is a pregnancy that “extends to 42 weeks of gestation or beyond.”  Maternal complications associated with post-term pregnancies are often underestimated, but physicians must make decisions to ensure that the mother and baby remain as healthy as possible.
In most instances, doctors are supposed to consider induction in order to avoid injuries and medical disorders associated with post-term pregnancies.
Post Term Pregnancy Complications
Fetal macrosomia is the medical term for babies who are larger than the average infant of their gestational age. Fetal macrosomia is diagnosed when a baby weighs more than 8 pounds, 13 ounces. 
Fetal macrosomia can pose health risks to both infants and mothers. For instance, it can cause vaginal tissue and perineal muscle tearing, as well as excessive bleeding after birth. It can also cause uterine rupture, a serious complication that occurs when the uterus tears open, causing the baby to move into the mother’s abdomen.
Doctors are more likely to use birth-assistive tools, such as forceps or a vacuum extractor, during the delivery of a large baby. Birth-assistive tools have been known to cause injuries to babies, such as brain damage, skull fractures, nerve damage, bruising, and swelling.
When babies are too large for their age, they can get stuck in the birth canal. Doctors must make sure the appropriate steps for delivery are taken as soon as possible, or the infant could end up losing oxygen, which can lead to cerebral palsy.
Meconium Aspiration Syndrome
According to the National Library of Biotechnology Information, meconium aspiration syndrome occurs in 12% of live births.  It happens when a baby breathes a mixture of meconium (their first stool) and amniotic fluid.
Meconium aspiration syndrome generally happens due to post-term gestational age, when the infant can have a bowel movement while still in utero. Meconium can also be passed if the fetus is in distress.
The amniotic fluid can then become mixed with the feces and cause brain damage and medical problems when the infant inhales the mixture.
Umbilical Cord Compression
During the later stages of pregnancy, a baby tends to move around more energetically. Amniotic fluid is likely low by the time a mother reaches post-term pregnancy, which can cause umbilical cord compression when the infant doesn’t have the additional fluid for protection.
When the umbilical cord is compressed, the baby can be deprived of oxygen, blood flow, and nutrients, which, in turn, can lead to cerebral palsy.
Oligohydramnios occurs when the baby doesn’t have enough amniotic fluid during pregnancy, which can lead to a host of medical problems. As mentioned earlier, low amniotic fluid has been associated with post-term pregnancy.
Along with umbilical cord compression, oligohydramnios can lead to meconium aspiration, brain damage, lung issues, and hypoxic-ischemic encephalopathy (HIE). If a physician fails to diagnose and manage a mother with oligohydramnios, it can also lead to an increased risk of fetal death.
If oligohydramnios happens prior to post-term pregnancy, the American College of Obstetricians and Gynecologists (ACOG) recommends hospital admission and delivery of the baby by at least 36 to 37 weeks gestation. 
Birth asphyxia, also known as hypoxic-ischemic encephalopathy (HIE), occurs when an infant doesn’t have enough oxygen in their blood flow and/or if their blood flow is restricted. 
HIE can be caused by several of the aforementioned issues, including oligohydramnios, umbilical cord compression, and prolonged labor. It can also occur when a baby is lodged in a mother’s pelvis and a physician fails to schedule and carry out an emergency C-section.
Other medical issues and complications that can arise due to post-term pregnancy include:
- Shoulder dystocia
- Stillbirth or neonatal death
Prevention of Post-Term Pregnancy Injuries
Doctors ultimately make the decision on how to proceed once a mother enters into post-term pregnancy. Therefore, it’s important to speak with your physician about any previous pregnancies that were late and any concerns that you may have.
Your physician should also go over the risk factors of post-term pregnancy, which in part, include obesity, maternal age, genetic factors, race, and sex of the baby (male infants are more likely to be born post-term) 
Keep in mind that any of the complications that are not handled with the appropriate standard of medical care can lead to potentially serious, lifelong complications and disorders for the infant.
- Postterm pregnancy. (n.d.). U.S. National Institutes of Health. PubMed Central (PMC).
Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3991404/
- Fetal macrosomia - Symptoms and causes. (2020, May 29). Mayo Clinic.
Retrieved from: https://www.mayoclinic.org/diseases-conditions/fetal-macrosomia/symptoms-causes/syc-20372579
- Katz, V., & Bowes, Jr., W. A. (n.d.). Meconium aspiration syndrome: reflections on a murky subject. National Library of Biotechnology Information. PubMed.
Retrieved from: https://pubmed.ncbi.nlm.nih.gov/1733193/
- Collins, J. (2012). Umbilical cord accidents. BMC Pregnancy and Childbirth.
Retrieved from: https://bmcpregnancychildbirth.biomedcentral.com/articles/10.1186/1471-2393-12-S1-A7#B6
- Medically indicated late-preterm and early-term deliveries. (n.d.). American College of Obstetricians and Gynecologists (ACOG).
Retrieved from: https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2019/02/medically-indicated-late-preterm-and-early-term-deliveries
- Hypoxic ischemic encephalopathy: Pathophysiology and experimental treatments. (1, September). U.S. National Institutes of Health. PubMed Central (PMC).
Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3171747/
- Postmaturity in the newborn - Health encyclopedia - (n.d.). University of Rochester Medical Center.
Retrieved from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02399