Pregnant women are often particularly susceptible to respiratory infections and, once infected, can become seriously ill, with long-lasting consequences for both mother and baby.

Is that true for the new coronavirus?

The information available so far is thin, but it appears that pregnant women are no more likely than anyone else to have severe symptoms from the coronavirus. In an analysis of 147 women , only 8 per cent had severe disease, and 1 per cent were in critical condition, according to a report published by the World Health Organisation.

It is too soon to know the consequences for these women’s babies. But so far at least, infants born to women with an infection seemed free of the virus and appeared healthy at birth, according to a study of nine pregnant women and their babies published last month in the Lancet. “Fortunately, there was no evidence of vertical transmission from mother to child,” said Dr Wei Zhang, an epidemiologist at Northwestern University and one of the Lancet study’s authors.

But as Zhang himself noted, the study is small. And it does not offer any clues to the infection’s effect on women in earlier stages of pregnancy. Fevers in early pregnancy are associated with birth defects and with some developmental conditions. And some viruses can have devastating consequences for the foetus. Zika, for example, can lead to an unusually small head, and Ebola can be lethal.

The trend in pregnant women infected with Sars, the closest relative of the new coronavirus, is no more reassuring. In one small study of 12 pregnant women in Hong Kong who developed Sars during the 2003 outbreak, three died, and four of the seven women who were in their first trimester had a spontaneous miscarriage.

While the Lancet study of nine pregnant women found no evidence of the virus in their babies, on Saturday, March 14th, it emerged that a newborn baby tested positive for coronavirus in the UK. The child’s mother, who was taken to a north London hospital days before the birth with suspected pneumonia, also caught the virus. The mother tested positive at North Middlesex hospital, in Enfield, with results coming through after the birth. The baby was tested for Covid-19 minutes after being born.

Reason for optimism

The WHO’s statistics for the new coronavirus and Zhang’s study both offer reason for optimism, but data from bigger numbers is crucial, experts said. “We do know that we’re going to have lots of pregnant women with coronavirus, just given the number of cases,” said Dr Denise Jamieson, chair of gynaecology and obstetrics at Emory University. “It’s going to be critical that surveillance systems collect information on pregnancy status.”

If women in earlier stages of pregnancy do turn out to be at risk, they will be prime candidates for a vaccine

Pregnant women should take the same precautions as everyone else but let their doctors know immediately if they are experiencing any symptoms, Jamieson said.

The infected mothers in Zhang’s Lancet study were isolated from their infants. All nine women gave birth by Caesarean section to minimise the newborns’ exposure to the virus.

Zhang’s collaborators in Wuhan, the epicentre of the epidemic, tested cord blood, throat swabs from the infants, breast milk and amniotic fluid. “We did not see any evidence for the virus,” Zhang said.

‘Healthy baby’

In other reports of infected babies, including a study of 10 newborns with serious complications, the infants were either tested hours after they were born or may have had direct contact with the infected mothers because the women were not diagnosed before delivery, Zhang said. “If we have proper isolation and strict protocol, there should be good chance to have a healthy baby,” he said.

Zhang was careful to emphasise that his study offers “good news” only to women in late pregnancy. “We don’t know the real effect of the virus on women in early pregnancy,” he said.

If women in earlier stages of pregnancy do turn out to be at risk, they will be prime candidates for a vaccine. The first major trial for a vaccine is expected to begin later this month, but its criteria exclude pregnant women.

Their exclusion is appropriate for this stage of vaccine development, said Dr Ruth Karron, a vaccinologist at Johns Hopkins University and one of the co-leaders of the “Prevent” guidance for including pregnant women in clinical trials. For a vaccine to be offered to pregnant women, scientists must first balance the risks and benefits; in this case, she said, both are unknown. The researchers would need to know the nature and prevalence of the disease in pregnant women, as well as any potentially dangerous side effects from the vaccine, such as fever.

But as researchers learn more, researchers should plan to include pregnant women in later iterations of the trial, Karron said: “This first trial is just that – it’s a first trial.” – The New York Times