Placenta's Role in Pregnancy Loss: Study

Researchers discovered that placental testing resulted in the accurate pathologic assessment of more than 90 per cent of previously unexplained pregnancy losses, a finding that they suggest may inform future prenatal treatment.

The research was published in the journal Reproductive Sciences.

In the United States, roughly 5 million pregnancies terminate in miscarriage (a loss happening prior to 20 weeks of gestation) and over 20,000 ends in stillbirth at or after 20 weeks of gestation. As many as 50 per cent of these losses are classified as "unspecified."

According to senior author Dr Harvey Kliman, a research scientist in the Department of Obstetrics, Gynaecology, and Reproductive Sciences at Yale School of Medicine, patients who suffer such pregnancy outcomes are frequently told that their loss is unexplained and that they should simply try again, which contributes to patients' feelings of responsibility for the loss.

“To have a pregnancy loss is a tragedy. To be told there is no explanation adds tremendous pain for these lost families,” said Kliman, who is also director of the Reproductive and Placental Research Unit.

“Our goal was to expand the current classification systems to decrease the number of cases that remained unspecified.”

For the study, Kliman worked with Beatrix Thompson, currently a medical student at Harvard University, and Parker Holzer, a former graduate student in Yale’s Department of Statistics and Data Science, to develop an expanded classification system for pregnancy losses based on pathologic examination of loss placentas.

The team started with a series of 1,527 single-child pregnancies that ended in a loss and were sent to Kliman’s consult service at Yale for evaluation. After excluding cases without adequate material for examination, 1,256 placentas from 922 patients were examined.

By adding the explicit categories of “placenta with abnormal development” (dysmorphic placentas) and “small placenta” (a placenta less than the 10th percentile for gestational age) to the existing categories of cord accident, abruption, thrombotic, and infection.

“This work suggests that the over 7,000 small placentas per year associated with stillbirths could have been detected in utero — flagging those pregnancies as high risk prior to the loss,” said Kliman. “Likewise, the identification of dysmorphic placentas may be one way to potentially identify genetic abnormalities in the almost 1 million miscarriages that occur in our country every year.”

He added, “Having a concrete explanation for a pregnancy loss helps the family understand that their loss was not their fault, allows them to start the healing process, and, when possible, prevent similar losses — especially stillbirths — from occurring in the future.”