Placental Pathology as Cause of Preterm Labor

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Preterm labor is caused by a variety of causes. One cause is placental pathology or an inadequately functioning placenta. Preterm labor arising from placental ischemia (part of the placenta has had interruption of the blood supply and that part of the placenta has died and is no longer functioning) or infection has a higher perinatal complication rate than idiopathic preterm labor (preterm labor which arises without any apparent cause). Preterm birth occurs in 5-13% of pregnancies in the US. Two thirds of these preterm deliveries are due to onset of preterm labor or premature rupture of membranes. The remaining one third are due to early deliveries by the provider for medical indications like preeclampsia.

Preterm infants are more likely to experience breathing and feeding problems. They are also at greater risk for cerebral palsy, learning disabilities, poor vision and hearing.

Most of the preterm labors are caused by placental insufficiency (which is discussed in another post on this site). Signs of preterm labor include more than five contractions in an hour, early spontaneous rupture of membranes, vaginal bleeding, excessive vaginal mucous, low back pain or generalized abdominal pain. You should contact your provider immediately if you are having these symptoms. Other placental causes of preterm labor include placental abruption, placenta previa, and chorioamnionitis (infection of the membranes surrounding the infant).

Treatment for the preterm labor will depend on what placental condition initiated the labor. Generally, the rule of thumb is to stop the labor and allow the infant to stay in the uterus as long as possible both for growth and fetal lung maturity. Your provider will probably use intravenous magnesium sulfate to halt the labor. But again, this all depends on the underlying pathology. If the preterm labor is due to a placental abruption and the abruption is getting larger, your provider may have to deliver the baby as this condition can be life threatening for the mother and the infant.

Following the delivery of the infant, it is important to examine the placenta visually and under a microscope to attempt to determine what the underlying cause of the preterm labor was. This is important for the management of the newborn. For example, the pediatrician or neonatologist would manage the infant care differently depending on whether the placenta showed signs of infection or not. The findings can also be valuable for managing future pregnancies.

The placenta has long been regarded as the ultimate disposable organ. There has been a tendency to deliver the placenta, and then cast it aside after performing a cursory inspection. The reality is the placenta is a complex organ that can sometimes hold the key as to why a pregnancy and delivery were complicated.

Another indicator that can be used to predict maternal and fetal outcome is placental calcification. This is a condition that is diagnosed by ultrasound. Predictive risks involving placental calcification include postpartum hemorrhage, maternal transfer to the ICU, low Apgar score, neonatal death and preterm labor. Placental calcification found prior to 32 weeks gestation is associated with an unfavorable pregnancy outcome. Placental calcification found between 32 and 36 weeks gestation is not associated with an adverse pregnancy outcome.

The University of Texas at Galveston found a strong association between premature placental aging and preterm births. Premature placental aging can occur due to smoking, high blood pressure, diabetes, and exposure to environmental toxins. Small bacteria known as nanobacteria can also cause premature placental aging. These are the same bacteria that cause kidney stones. Taking prenatal vitamins and antioxidants seem to help prevent placental aging.

Preterm births are costly emotionally, physically, and economically. More intense research and understanding on the placental anatomy and physiology will hopefully help reduce the incidence of preterm labor and deliveries.

Wishing you a happy and problem free delivery, Pablo.

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