CHICAGO - The placentas of multiple women who tested positive for COVID-19 showed signs of injury, according to a new Northwestern Medicine study published Friday.

The two major findings about the placenta injuries include an increase in maternal vascular malperfusion, a medical term that means the blood circulation on the maternal side of the placenta is abnormally delivering the same amount of oxygen to the fetus, and blood clotting within the placenta.

"That's really concerning because we see that same placental finding in a lot of disease states, like fetal growth restriction, preterm birth, preeclampsia or even stillbirth," said Dr. Emily Miller, a co-author of the study and a Northwestern Medicine obstetrician. "Seeing this, even acutely in the setting of SARS-CoV-2 infection, makes us worried that this virus may be affecting the placenta."

Miller said there have been a lot of reports of blood clots during COVID-19 with the general population of patients, and finding clots in the placenta "is kind of the placenta version of that same phenomenon."

The placenta, which develops alongside the fetus to support ongoing and safe growth, acts as the kidneys and the lungs of the fetus while it's inside the uterus, explained Miller. The placenta supplies all of the baby's oxygen, breathes off all the carbon dioxide, supplies all of the baby's nutrients, and eliminates all metabolic waste.

Because the placenta plays such an integral part in healthy fetus development, studying it in pregnant women who had COVID-19 can help determine if the virus can cause certain outcomes.

There have been many epidemiological reports of pregnant women who tested positive for COVID-19 and had pregnancy complications, like preterm birth or preeclampsia. It's hard to know if COVID-19 was the cause of those conditions though because they're so common, explained Miller.

"We often will see some changes in the placenta that can lead ultimately to these clinical manifestations," said Miller. "Trying to look at this intermediate piece, and decide if that intermediate piece is affected, gives us some more support to say, 'These pregnancies in women who are infected with SARS-CoV-2 might be at risk.'"

The study examined the placentas of 16 women who tested positive for COVID-19. Ten of the women received their positive diagnosis when arriving for labor and delivery, and the others got their positive COVID-19 results one to five weeks prior to giving birth, according to the study.

Fourteen patients gave birth at full-term, and one patient delivered prematurely. One patient had a stillbirth at 16 weeks, but doctors can't say if COVID-19 was a cause. All of the babies who were born tested negative for COVID-19 and were normal, healthy weights, the study said.

All of the women gave birth at Northwestern Medicine Prentice Women's Hospital, and their placentas were examined immediately after delivery.

Miller, who is also an assistant professor of obstetrics and gynecology at Feinberg, emphasized not wanting to overstate the findings since the study is small. "It's super preliminary," she said.

Yet, she and her co-authors felt it was important to get the information out. The findings could point to a potential need for more surveillance of pregnancies that are impacted by COVID-19, she said. Miller says that looks like monitoring a fetus' growth more closely as a pregnancy progresses.

"Fetal growth is one of our good measures of how well the placenta is working in terms of giving oxygen and nutrients to the baby," said Miller, "so if the growth is OK, that might give us reassurance. Normally in pregnancy, we use a measuring tape to measure how tall the uterus is, but that may not be accurate enough in these settings because the risk might be higher."

Miller and her colleagues have been extremely discerning in the best ways to practically move forward at Prentice with this new information. They don't want to cause more harm than good, she said, so she and her colleagues have been examining various potential risks.

"Our group has decided that we are going to do growth ultrasounds because their risk of a false positive result, with all the additional things we can do, is pretty low," said Miller. "Then we would use that to inform if we need to change anything else with respect to monitoring the baby."

Women who are pregnant and diagnosed with COVID-19 should speak with their obstetrician and consider additional monitoring to ensure the health of their baby, Miller said.

"That's being extremely conservative and acting quicker on findings than we typically do, but unfortunately we're not in a situation where we have any time to spare," said Miller. "So while there's no formal guidelines that recommend this overtly, hopefully this (study) will contribute to other bodies potentially reconsidering and going ahead and recommending additional surveillance."

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