The Placenta Can Explain Many Unexpected Pregnancy Losses

Scientists reveal that more than 90% of previously unexplained pregnancy losses were accurately identified pathologically by placental examination.

The finding, conducted by researchers from Yale and published in Reproductive Science, may guide future prenatal treatment.

In the United States, there are about 5 million pregnancies yearly, of which 1 million result in miscarriage and more than 20,000 result in stillbirth at or after 20 weeks. Up to 50% of these losses fall under the "unspecified."

According to senior author Dr. Harvey Kliman, a research scientist in the Department of Obstetrics, Gynecology, and Reproductive Sciences at Yale School of Medicine, patients who experience such pregnancy outcomes are frequently told that their loss is unexplained and should try again.

Kilman says that it is tragic to lose a pregnancy. The fact that there is no explanation only makes these lost families' suffering worse. To reduce the number of unclassified cases, the team sought to broaden the scope of the existing classification schemes.

Uncovering the study

To achieve the study, Kliman collaborated with Parker Holzer, a graduate student at Yale's Department of Statistics and Data Science, and Beatrix Thompson, a current medical student at Harvard University, to create an expanded classification system for miscarriages based on pathologic examination of loss placentas.

The team's initial set of 1,527 single-child miscarriages sent to Kliman's consult service at Yale for analysis formed the basis of their research. One thousand two hundred fifty-six placentas from 922 patients were evaluated after cases without sufficient material for investigation were eliminated. Of these, 30% were stillbirths and 70% were miscarriages.

The authors identified the pathologic diagnoses for 91.6% of the pregnancies, including 88.5% of miscarriages and 98.7% of stillbirths, by adding the explicit categories of "placenta with abnormal development" and "small placenta."

Dysmorphic placentas, a pathological sign linked to genetic disorders, were the most prevalent pathologic finding in cases with unexplained miscarriages (86.2%). A tiny placenta was the most pervasive pathologic finding in unexplained stillbirths (33.9%).

As a result of this research, Kilman concludes that it may have been possible to identify the roughly 7,000 tiny placentas annually linked to stillbirths in utero, identifying those pregnancies as high risk before the loss.

Similar to this, identifying dysmorphic placentas could be one technique to discover possible genetic defects in the over 1 million miscarriages that take place in our nation each year.

Having a clear explanation for a pregnancy loss, he continued, aids the family in realizing that the loss was not their fault, enables them to begin the healing process, and, where feasible, helps prevent future occurrences of the same failures, particularly stillbirths.