Pregnant women with Covid in their last trimester are three times as likely to give birth early - a risk that rises to seven-fold for those after their 34th week of pregnancy, a new study reports.
The Israeli study of more than 5,000 mums-to-be is one of the first to look at pregnancy outcomes for Covid patients by trimester. Researchers advised mums-to-be to wear masks and social distance to reduce their risk of infection.
For Covid infections in the first and second trimesters, the study found no association with increased risk of preterm birth. It also reported no difference in the chances of losing a baby between infected and non-infected women.
Previous studies of Covid during pregnancy have been small, generally limited to patients who are in hospital, and have often not reported outcomes depending on infection during different stages of pregnancy, Wales Online reported.
Premature birth is defined as a child born before the 37th week of pregnancy or earlier.
Women infected in their third trimester were 2.76 times more likely to give birth prematurely – while women infected after 34 weeks of gestation were over seven times more likely to experience preterm birth.
The findings, published in the journal PLOS One, showed a lower rate of waters breaking before labour began in infected women (39.1 per cent) compared to non-infected women (58.3 percent), and proportions of caesarean sections and baby loss were similar in both groups.
Because of the increased risk of preterm birth in women infected during late pregnancy, the researchers suggest that during their third trimester, and particularly after 34 weeks of gestation, they should be advised to social distance and wear masks to reduce risk of infection.
Dr Tal Patalon, head of Kahn-Sagol-Maccabi (KSM), said: "The results are encouraging and reassuring that Covid-19 infection during pregnancy is not associated with any type of pregnancy loss. However, it should be remembered that the research group tested the Covid pre-Delta variants, and does not refer to the dominant variant today, which is Omicron."
She added: "We continue to conduct research to provide real-world data and knowledge to the public and decision-makers."
Biostatistician and epidemiologist Noga Fallach and her colleagues at the Kahn-Sagol-Maccabi Research and Innovation Centre used anonymised data captured by Maccabi Healthcare Services in Israel to match 2,753 women who were infected during pregnancy with 2,753 women without reported Covid-19 infections.
The study ran from February 21, 2020, until July 2 last year. Of the infected women, 17.4 per cent caught Covid during the first trimester, 34.2 per cent during the second and 48.4 per cent during the third trimester.
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