The coronavirus may damage the placenta during pregnancy, according to a study of 16 pregnant women

Pregnant women who contract COVID-19, the disease the novel coronavirus causes, seem vulnerable to a complication that damages the placenta and can disrupt how oxygen and nutrients are delivered to the fetus. 

Still, the virus itself doesn't seem to transmit in utero. 

The small study out of Northwestern Medicine Prentice Women's Hospital in Chicago looked at the placentas of 16 pregnant women who were COVID-positive.

All had damage, and one pregnancy ended in miscarriage, though it's unclear if or how the damage affected that outcome. Of the 15 other women who delivered healthy babies, 12 (or 80%) had vascular malperfusion, a condition that can limit blood flow between the mom and fetus, and six (or 40%) had placental blood clots.  

Though a very small sample size, that's significant considering 55% of women in a comparison group (who didn't have COVID-19) experienced vascular malperfusion and only 9% had placental blood clots. 

"These findings support that there might be something clot-forming about coronavirus, and it's happening in the placenta," Dr. Jeffrey Goldstein, a Northwestern pathologist and study author told Reuters. That could lead to growth issues in utero or, in severe cases, central nervous system injury or stillbirth. 

In this group, however, the outcomes were largely positive: The 15 women delivered healthy, COVID-negative babies who shouldn't experience any long-term negative impact, Dr. Stephanie Ros, an OB-GYN and maternal-fetal medicine specialist at the University of South Florida's Morsani College of Medicine, told Insider. 

Rather, the findings may mean "we should treat pregnancies affected by COVID-19 similarly to the way we treat women with illnesses like hypertension, and do fetal monitoring or growth assessment of the fetuses on a more frequent basis compared to healthy women," she said. 

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Crystal Cox/Business Insider; Samantha Lee/Business Insider

The American College of Obstetricians and Gynecologists has long considered pregnant women a high-risk population for COVID-19, since they're at greater risk of severe morbidity and mortality from any respiratory infection, including like the flu. 

Experts have also known that COVID-19 can also make it more likely for pregnant women to have complications, namely preterm birth, according to the CDC.

But one positive that's come out of the research is that it seems highly unlikely COVID-19 positive moms can pass the virus on in utero — even though it seems to attack the placenta. There's also no evidence the virus spreads through breastmilk, and the substance's antibodies may even help develop a future treatment for people of all ages. 

And, while babies and children can acquire COVID-19, presumably after birth, they seem less vulnerable than older populations. 

In a study out March 17 of 2,000 kids in China who were diagnosed with COVID-19, researchers found 90% were either asymptomatic or had mild or moderate COVID-19 symptoms, like fever, fatigue, sore throat, cough, or shortness of breath. Just over 10% of all infants in the study ended up in a severe condition. 

Experts recommend pregnant women with COVID-19 plan to give birth in a hospital, where staff must follow CDC recommendations for managing them and their newborns to reduce the risk of transmission after birth. That may mean putting moms and their babies in separate isolation rooms, or keeping mom and newborn six feet apart.