Post-term pregnancy: Causes and Risks

Post-term pregnancy
Post-term pregnancy: Causes and Risks

Post-term pregnancy is defined as a pregnancy that has extended to or beyond 42 weeks (9 months) of gestation, or when the mother-to-be is 14 days ahead of the estimated date of delivery. Generally, after the mother-to-be completes 37 weeks of pregnancy, we consider it as a term pregnancy.

CAUSES: The most common cause of prolonged pregnancies is inaccurate dating. So the first thing to do when you suspect that pregnancy is reaching ‘postdates’ i.e. beyond 40 weeks of pregnancy duration, is to check the mother’s last period dates. The cause of post-term pregnancy is usually unknown. Risk factors which may be associated with it are –if it is the first baby, previous post-term pregnancy, if you are carrying a male fetus, if the mother-to-be is obese, hormonal factors and genetic causes.

COMPLICATIONS AND RISKS: There are risks associated with the pregnancy continuing beyond 42 weeks of gestation; risking the lives of both the mother and to the baby

  • Increased risk of babies being stillborn or dying in the immediate few days after birth, at 42 weeks of gestation the risk is twice as high as against that at full term (37 weeks)
  • There is an increased risk of intrauterine infection to the baby
  • There is an increased risk of the poor blood supply to the baby via the placenta, leading to lack of oxygen delivery to the baby. This, in turn, can cause the baby to pass stool (Meconium) inside the mother’s uterus in the Amniotic Fluid. This could lead to the development of Pneumonia in the baby, due to aspiration of the Meconium into the Lungs
  • Risk of Fetal Macrosomia i.e. big baby (birth weight >4.5 kg) also persists, and during delivery, such babies may sustain injuries or the mother may have vaginal tears or excessive post-partum bleeding. The baby’s shoulder or head may get stuck during delivery, or the labour may get prolonged.

About 20% of post-term fetuses have Dysmaturity Syndrome, which means babies are born with physical features as those of babies with Intrauterine growth retardation (IUGR) i.e., like babies who stop growing appropriately inside the uterus lowing from lack of adequate blood supply via the Placenta. This includes thin wrinkled peeling skin (excessive desquamation), thin body (malnourishment), long hair and nails, Oligohydramnios (deficiency of amniotic fluid) and passage of Meconium (baby stool). These pregnancies are at bigger risk of Umbilical Cord compression from Oligohydramnios, and short-term neonatal complications such as Neonatal Depression, Hypoglycemia (very low level of blood sugar), seizures, and respiratory insufficiency. Increased risk of long-term brain damage in the child is a possibility.

MANAGEMENT:

  • Accurate pregnancy dating is crucial to the diagnosis and management of post-term pregnancy
  • Routine ultrasound examination for pregnancy dating reduces the rate of false-positive diagnosis. First-trimester sonography is the best for dating the pregnancy.
  • Prevention of post-datism by induction of labour seems to be the best management. The gestation at which this is to be done varies as per the protocol of different hospitals. But, in view of current scientific evidence, it is ideal to not let the pregnancy to continue beyond 41 weeks of gestation and induce labor then; keeping in mind the risk goes on increasing after 38-39 weeks. After 38-39 weeks, one should ask their Gynecologist about the need for Antenatal Fetal Surveillance by doing Non-stress Test (NST) to ensure that the baby is growing healthily.

The golden rule is to follow the doctor’s advice and know that they will always try to make the best possible decision for the fetal-maternal unit as a whole.


Inputs by Dr. Asmita Mahajan, Consultant Neonatologist & Pediatrician, SL Raheja Hospital, Mahim – A Fortis Associate

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