The risk of stillbirth is about twice as high for pregnant women with Covid-19 than for those who have not contracted the disease, according to a large study by US health authorities published on Friday.
The Centers for Disease Prevention and Control (CDC) analyzed more than 1.2 million deliveries between March 2020 and September 2021, from a database of hospitals.
The public health agency considers a stillborn child from the 20th week.
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In general, stillbirths were rare (0.65% of births, or about 8,150). But the risk of stillbirth was 1.90 times higher in women with Covid-19. Concretely, over this period, 1.26% of births were a stillborn child for women who contracted Covid-19, against 0.64% for others. The Delta variant also increased this risk, noted the CDC, which analyzed the periods before and after this variant became dominant in the country, in July 2021.
Compared to uninfected women, the risk was thus increased by 1.47 for mothers positive for Covid-19 during the pre-Delta period, and by 4.04 once the variant was majority.
"Further studies are needed to examine the role of maternal complications from Covid-19 on the risk of stillbirth
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the CDC wrote. Some studies have in the past suggested that the cause is inflammation and decreased blood flow to the placenta.
The CDC study is the most important to have demonstrated the link between stillbirths and Covid-19 to date, they stressed.
They said she could not determine whether the women with Covid-19 were sick at the time of their hospitalization, or whether they had been infected previously.
The immunization status of the women was also not available.
US health authorities strongly recommend that pregnant women be vaccinated against Covid-19, before or during their pregnancy.