Coronavirus: What we know so far about risks to pregnancy and babies

Pregnant people don't seem to be at greater risk of experiencing severe covid-19, and the virus doesn't seem to pass to fetuses, but there's still a lot we don't know

As cases of covid-19 continue to multiply around the world, we are all being advised to take precautions to avoid getting infected, whether that is singing your favourite 20-second tune while washing your hands, avoiding non-essential travel or working from home. But what about people who are pregnant? And are their babies at risk?

So far, information is relatively scant. Pregnant people in China who are diagnosed with the coronavirus are treated in designated hospitals, and the handful of published reports of such cases only cover tens of people. However, initial reports suggest that covid-19 might not hit pregnant women or their newborn babies too heavily.

One reason to worry about covid-19 in pregnancy is that people are more likely to become severely ill with flu when they are pregnant.

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That is partly because pregnancy suppresses a person's immune system. Additionally, in the later stages of pregnancy, the fetus and uterus can start squashing other organs, including the lungs. As a result, some areas of the lungs become less able to circulate air, leaving them more prone to infection.

Some kinds of infection also seem to put the fetus at risk. Prolonged, high fevers in pregnancy, particularly in the first trimester, have been linked to some birth defects. "With any viral infection during pregnancy, the fetus is at risk of miscarriage, stillbirth, growth restriction, malformation," says David Baud at Lausanne University Hospital in Switzerland.

There is some evidence that pregnant women are more at risk of serious illness from MERS and SARS - viruses that are similar to the new coronavirus - and that these infections also increase the risk of miscarriage. But it is difficult to say for sure though, because only a handful of pregnant people have been reported to be infected with those viruses, and miscarriages occur in about a quarter of all pregnancies.

New case studies

A report published today, by Yalan Liu at Huazhong University of Science and Technology, in China, and her colleagues, covers four women who were infected with the virus when they gave birth to their four babies. All four women were ill with the virus when they gave birth. But the four babies were born healthy, without any covid-19 symptoms.

One baby had mild problems with breathing but recovered well after a few days of treatment. Two had rashes but these disappeared within 10 days without treatment. Three of the babies were tested for the virus - none of them had it.

Another study, covering nine women who gave birth to 10 babies, reports more mixed outcomes. Nine babies survived, and none tested positive for the new coronavirus, but six were born with shortness of breath and two had fever.

Other reports have been more reassuring, says Pat O'Brien, vice president of the Royal College of Obstetricians and Gynaecologists (RCOG) in the UK. A report covering 15 women who had had covid-19 during pregnancy found no evidence that the women had worse symptoms than women who weren't pregnant. "In this report, the pregnant women achieved a good recovery without the use of antiviral drugs," the authors write.

By the time that study was written, 11 of the women had given birth, and none of their babies had been born infected.

"At the moment, there's no evidence whatsoever that there's an increased risk of miscarriage," says O'Brien, who co-authored RCOG's new guidance on covid-19 in pregnancy, published on 9 March. "But we're desperate for more information." The guidelines will be updated regularly as more information becomes available, he says.

Newborn separation

Doctors in China have been cautious, and people who are diagnosed with the virus shortly before giving birth have been separated from their newborn babies for two weeks. These infants have been formula fed, and appear to be healthy.

The US Centers for Disease Control and Prevention is recommending similar measures. But the UK's RCOG is not. "It is a very difficult decision and a question of balancing pros and cons," says O'Brien, whose team has been collaborating with the UK Royal College of Paediatrics and Child Health. "If you separate the mother and baby, you lose all the benefits of bonding and better breastfeeding."

"The Royal College of Paediatrics and Child Health took the view that, on balance, the benefits of keeping the mother and baby together outweigh the risks of the mother giving the infection to the baby," says O'Brien.

Early reports suggest that the virus doesn't pass from mother to baby via breastmilk. But health bodies are advising new mothers who are infected with the virus to take precautions while breastfeeding, such as washing their hands and wearing a face mask.

In fact, people who recover from the virus before giving birth will develop antibodies against it - and may give their babies some protection against the virus by breastfeeding. In this way, such babies could technically be the first to receive any kind of vaccine against the virus, says O'Brien.

But O'Brien, his colleagues and their counterparts around the world don't have any definite answers, and are awaiting new data collected by hospitals treating pregnant people and new mothers. "We still have so little information," says O'Brien.

In the meantime, Baud recommends that pregnant people ensure they are taking precautions to protect themselves from getting ill, such as avoiding crowded areas and frequent handwashing.

Baud also recommends that doctors continue to closely monitor people who are pregnant once they have recovered from an infection. "We propose, after maternal recovery, an ultrasound every two to four weeks," he says.