What We Know and Don’t Know About Coronavirus and Pregnancy

Now that the COVID-19 pandemic appears likely to continue for at least several months, expectant parents may be anxious about how the illness could affect their pregnancies and the health of their newborns.

Pregnant women are at higher risk for many infections because pregnancy suppresses the immune system. Some illnesses can impact the health of the fetus, but the risks of COVID-19 are not yet clear.

We spoke to UC San Francisco perinatologist Stephanie Gaw, MD, PhD, and pediatrician Valerie Flaherman, MD, MPH, about what we know and don’t know about COVID-19’s effects on pregnancy, the possibility of in utero transmission, and advice for pregnant women.

Gaw and Flaherman are part of the team leading the newly launched PRIORITY study, which is enrolling pregnant and recently pregnant women with COVID-19 to fill in the many gaps in our knowledge.

What do we know so far about COVID-19 and pregnancy? How much data do we have?

We still have very little data about pregnancy and COVID-19, said Gaw. We mainly have sparse case reports from China of around 30 pregnant women with COVID-19. The outcomes in those reports were relatively mild: all the women survived, they didn’t seem more likely to have severe illness, and there didn’t seem to be evidence of transmission to the baby during pregnancy.

Yet, Gaw said that based on what is known about pregnancy and other respiratory illnesses, she is concerned that pregnant women may be at higher risk for COVID-19.

“Even with the seasonal flu, pregnant women are more likely to get it than the general population and they’re at higher risk for more severe outcomes if they do get it,” said Gaw.

Similarly, in the H1N1 epidemic and the SARS epidemic, pregnant women were at higher risk for severe disease and death, she said. 

Based on the limited data from China, “we can say that you can have good outcomes, but it’s too early to say that it’s safe,” said Gaw.

Why are pregnant women at higher risk for respiratory infections in general?

One reason is that pregnant women are in a more immunosuppressed state, said Gaw. Decreased immune defenses are a normal physiologic response so that the mother’s body doesn’t reject the pregnancy itself.

“We see the effect in a lot of different infections,” said Gaw. “Pregnant women will have milder symptoms, but it also means that if a pregnant woman is symptomatic, she’s probably more sick than a non-pregnant person with the same symptoms.”

The physical changes during pregnancy also compress the diaphragm and reduce lung volumes overall, said Gaw. “So when there’s increased stress on the respiratory system, you have less backup to compensate for the increased work to breathe.”

Can the novel coronavirus be transmitted in utero, during birth, or through breastfeeding?

Some viruses can be passed from mother to fetus in utero, including  Zika, cytomegalovirus, rubella, and measles, and others during delivery, such as HIV, herpes and hepatitis – but respiratory viruses generally are not, said Gaw.

One study from China reported that out of 33 infants born to mothers with COVID-19, three tested positive days after birth, possibly through in utero transmission. Other studies have hinted at the possibility of in utero transmission based on elevated levels of certain antibodies, although the newborns tested negative for the virus.

Gaw said there is not yet enough evidence to confirm whether or not the novel coronavirus can be transmitted in utero. “The possibility is definitely there,” she said.

According to the U.S. Centers for Disease Control and Prevention, the coronavirus has not been detected in breastmilk, but it is not yet known whether the mother can transmit COVID-19 this way.

What questions is the PRIORITY study hoping to answer?

With much still unknown about COVID-19 and pregnancy, researchers hope the nationwide PRIORITY study will provide some answers.

Women who are pregnant or were pregnant in the last six weeks and have confirmed or suspected COVID-19 can enroll from anywhere in the country. Suspected cases that test negative can still be enrolled as a comparison group. Participants will take surveys online or by phone and participating hospitals may collect specimens such as maternal blood, amniotic fluid, placentas, cord blood and breast milk, said Flaherman.

The study will help us understand the clinical course of COVID-19 in pregnant women, said Gaw. “We know that for the flu, recovery time is much longer because of the attenuated immune system.” It will also help us understand the risk for complications such as birth defects, miscarriage or preterm labor, as well as effects on newborn health.

The study will likely provide the first data on infections that happen earlier in pregnancy. Because the new coronavirus appeared so recently, the only data so far are from infections in the third trimester.

“This is why we wanted to start the PRIORITY registry early and try to get as much data as early as possible before we miss the window,” said Gaw. “We hope to get information to help people that are sick now, that may be sick in the next few months, and also for the future epidemics that are almost sure to happen.”

What precautions is UCSF Health taking for its pregnant patients?

At UCSF Health, any pregnant patient with symptoms such as fever, cough, malaise, or contact with a confirmed case would be tested for COVID-19, said Gaw. “We are lucky to have testing available,” she said.

Special isolation rooms have been prepared for patients who deliver while positive for COVID-19. “We are ready to take care of them,” said Gaw. Women in delivery are allowed one support person in the room.

At UCSF Health, if a woman is sick with COVID-19 while delivering her baby or develops symptoms after delivery, maternal-infant separation for a period of time may be recommended, said Flaherman. Doctors will discuss with her the appropriate options for separation and breastfeeding.

When appropriate, prenatal visits can be done through telehealth to minimize unnecessary exposure.

What can pregnant women and parents of newborns do to stay safe?

Based on what we know from other respiratory illnesses pregnant women should be considered a high-risk group for COVID-19, said Gaw.

“That doesn’t mean they should lock themselves in their rooms for their whole pregnancy.”

In addition to the social distancing and hygiene precautions everyone should take, she advises pregnant women to talk to their doctor even if they have very mild symptoms. In particular, she said that fevers should be controlled as quickly as possible because they may cause stress to the fetus. Prolonged fevers in the first trimester, when organ systems are still forming, are more likely to harm fetal development and lead to birth defects or miscarriage, she said.

Infants also are generally considered a high-risk group as well, said Flaherman, but she noted that the evidence so far suggests that COVID-19 does not focus on infants or children. She speculated that children’s less developed immune responses may actually help them fare better since many of the critical outcomes in adults have been associated with ARDS, or acute respiratory distress syndrome, an inflammatory reaction of the body to the pathogen.

Flaherman said that some newborn health care visits can now be provided through telehealth. For older infants needing immunization, she recommends parents contact their pediatrician’s office in advance to discuss ways to keep their baby safe during the visit, such as scheduling the first visit of the day, entering the facility through an alternate door, or skipping the waiting room to decrease exposure.