Early Research on COVID-19 in Pregnancy

Early Research on COVID-19 in Pregnancy
Building the data to inform evidence-based guidelines.

While much research into COVID-19 is focused on therapies, investigators worldwide are also attempting to answer key questions about the course of the disease in pregnant women and their newborns. Currently, maternity facilities are implementing widely different policies for labor and delivery, and infected women are receiving different guidance about contact with their infants and breastfeeding.¹

“There is still much we don’t know about COVID-19 in pregnancy. We are gaining information every day,” said Jennifer Thompson, M.D., assistant professor of obstetrics and gynecology at Vanderbilt University Medical Center.

Thompson is currently researching COVID-19 and pregnancy, and coordinating Vanderbilt’s participation in a U.S. registry called PRIORITY (for Pregnancy CoRonavirus Outcomes RegIsTrY) that is gathering data about infected pregnant women.

“There is still much we don’t know about COVID-19 in pregnancy. We are gaining information every day.”

Early Data

A large published case series reports on 43 pregnant women infected with the virus who were patients at two New York hospitals. Eighty-six percent had mild cases, 9.3 percent had severe cases, and 4.7 percent were critical. When these women presented for obstetric care or for delivery, 14 were asymptomatic. Ten of the asymptomatic women eventually developed symptoms, and their disease severity closely resembled severity among non-pregnant adults.

Pregnant women with underlying conditions such as respiratory illnesses or diabetes appeared to be more vulnerable to developing severe cases. “The majority of the pregnant patients with severe illness were obese, and almost 42 percent of them had a comorbid condition, with asthma most common, followed by diabetes and hypertension,” Thompson said.

In addition to the New York case series, much of what researchers now know about COVID-19 in pregnancy is from smaller international case series. “These case series yielded similar findings to the New York case series,” Thompson said.

No Proof of Vertical Transmission

Although several international cases have suggested that vertical transmission may have occurred, it has not been definitively proven that those babies were infected in utero, rather than by their mother or a health care worker soon after birth.

“So far, there’s been no evidence of vertical transmission through the placenta, with babies testing positive immediately upon delivery,” Thompson said.

“So far, there’s been no evidence of vertical transmission through the placenta, with babies testing positive immediately upon delivery.”

Still Cause for Concern

Thompson believes it would be premature to conclude that the infection in pregnant women behaves exactly as it does in non-pregnant individuals. Normal physiologic changes that occur during pregnancy could place pregnant women at increased risk of infection, she said.

While relatively little data about pregnant patients was collected during the SARS and MERS outbreaks, data about those coronavirus-caused illnesses are concerning. Pregnant women with SARS were likelier than other patients to need mechanical ventilation and die, Thompson says, and both infections are linked to higher rates of miscarriage and preterm birth.

Creating Data Registries

As of April 16, 300 women in the U.S. were enrolled in the PRIORITY registry. Vanderbilt is also creating its own data registry to track pregnant patients who have tested positive for COVID-19, and to study outcomes for them and their infants.

Another registry, the International Registry of Coronavirus Exposure in Pregnancy, is collecting data from dozens of centers worldwide.

The registries are an essential step to more reliable data and stronger studies, Thompson said. “When it comes to COVID-19 and pregnancy, what seems to be true today may not be true tomorrow as we continue to gain more information on the disease and pregnancy.”

“When it comes to COVID-19 and pregnancy, what seems to be true today may not be true tomorrow as we continue to gain more information on the disease and pregnancy.”