A University of Edinburgh study has revealed that women who have COVID-19 towards the end of their pregnancy are vulnerable to birth-related complications, and more likely to have complications than those who got infected in the earlier stages of pregnancy or who haven't had COVID at all.
The findings show that preterm births, stillbirths and newborn deaths are more common among women who have the virus 28 days, or less, before their delivery date.
Most complications, which also include COVID-related critical care admissions, occurred in unvaccinated women, according to one of the first national studies of pregnancy and COVID-19.
Researchers say more should be done to increase vaccine uptake in pregnant women, whose vaccination rates are much lower than those of women in the general population.
The team analysed data relating to all pregnant women in Scotland. They included more than 87,000 women who were pregnant between the start of vaccination uptake in December 2020 and October 2021.
Vaccination uptake during the study period was lower in pregnant women, compared with women aged 18 to 44 in the general population.
Some 32% of pregnant women who gave birth in October 2021 were fully vaccinated, meaning more than 14 days had elapsed since a second vaccine, compared with 77% of the general female population aged 18 to 44.
Since the start of Scotland’s vaccination programme, a total of 4,950 cases of COVID-19 have been confirmed during pregnancy, with 77% of these cases in unvaccinated women. Some 12% of COVID cases were in partially vaccinated pregnant women, who had only received one vaccine dose, or were diagnosed less than 14 days since their second dose.
This compared with 11% of cases in fully vaccinated women.
The team analysed data on extended perinatal deaths, defined as death of a baby in the womb after 24 weeks of pregnancy, or in the first 28 days after birth. They found the extended perinatal death rate among babies born within 28 days of their mother developing COVID-19 was 23 per 1,000 births.
All baby deaths occurred to women who were unvaccinated against COVID-19 at the time of infection.
A total of 17% of babies born within 28 days of their mother developing COVID-19 were delivered prematurely, more than three weeks before their due date.
These data were then compared with the background rates of extended perinatal deaths and preterm births, which are the rates for all babies born in Scotland regardless of whether their mother had previously had COVID-19 or been vaccinated.
The background perinatal mortality rate during the pandemic in Scotland was six per 1,000 and preterm birth rate was 8%.
Experts said it was not possible to say if COVID-19 contributed directly to the deaths or preterm births, as they did not have access to detailed clinical records for individual women.
Hospital and critical care admissions were also significantly more common in pregnant women with COVID, who were unvaccinated at the time of diagnosis, than in vaccinated pregnant women: 98% of women with COVID-19 during pregnancy who were admitted to critical care were unvaccinated.
The team also monitored complication rates in women who received a COVID vaccination during pregnancy.
The perinatal mortality and preterm birth rates in women within 28 days of receiving a vaccine were very similar to the background rates, at four per 1,000 and 8%, respectively, providing further reassurance on the safety of vaccination during pregnancy.
These findings are part of the COPS study, which provides population-based information for the whole of Scotland on the incidence and outcomes of COVID-19 infection and vaccination in pregnancy.
COPS is an offshoot of the EAVE II project, which uses anonymised linked patient data in Scotland to track the pandemic and the vaccine roll out in real time.
The research team included scientists from the Universities of Edinburgh, Glasgow, Aberdeen, Strathclyde, and St Andrew's; Public Health Scotland; and Victoria University of Wellington.
COPS co-lead Dr Sarah Stock, of the University of Edinburgh’s Usher Institute, who is also a consultant obstetrician, said: “Our data add to the evidence that vaccination in pregnancy does not increase the risk of complications in pregnancy, but COVID-19 does.
“COVID-19 vaccination in pregnancy is crucial to protect women and babies from preventable, life-threatening complications of the virus.”
The findings were published in Nature Medicine.
Study details
SARS-CoV-2 infection and COVID-19 vaccination rates in pregnant women in Scotland.
Sarah Stock, Jade Carruthers, Clara Calvert, Cheryl Denny, Jack Donaghy, Anna Goulding, Lisa. Hopcroft, Leanne Hopkins, Terry McLaughlin, Jiafeng Pan, Ting Shi, Bob Taylor, Utkarsh Agrawal, Bonnie Auyeung, Srinivasa Vittal Katikireddi, Colin McCowan, Josie Murray, Colin Simpson, Chris Robertson, Eleftheria Vasileiou, Aziz Sheikh, Rachael Wood.
Published in Nature Medicine on 13 January 2022
Abstract
Population-level data on COVID-19 vaccine uptake in pregnancy and SARS-CoV-2 infection outcomes are lacking. We describe COVID-19 vaccine uptake and SARS-CoV-2 infection in pregnant women in Scotland, using whole-population data from a national, prospective cohort. Between the start of a COVID-19 vaccine program in Scotland, on 8 December 2020 and 31 October 2021, 25,917 COVID-19 vaccinations were given to 18,457 pregnant women. Vaccine coverage was substantially lower in pregnant women than in the general female population of 18−44 years; 32.3% of women giving birth in October 2021 had two doses of vaccine compared to 77.4% in all women. The extended perinatal mortality rate for women who gave birth within 28 d of a COVID-19 diagnosis was 22.6 per 1,000 births (95% CI 12.9−38.5; pandemic background rate 5.6 per 1,000 births; 452 out of 80,456; 95% CI 5.1−6.2).
Overall, 77.4% (3,833 out of 4,950; 95% CI 76.2−78.6) of SARS-CoV-2 infections, 90.9% (748 out of 823; 95% CI 88.7−92.7) of SARS-CoV-2 associated with hospital admission and 98% (102 out of 104; 95% CI 92.5−99.7) of SARS-CoV-2 associated with critical care admission, as well as all baby deaths, occurred in pregnant women who were unvaccinated at the time of COVID-19 diagnosis. Addressing low vaccine uptake rates in pregnant women is imperative to protect the health of women and babies in the ongoing pandemic.
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COVID increases pregnancy and birth complications — French hospital study
COVID vaccination not linked to premature birth or unusually small babies – CDC study
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Effectiveness of Pfizer vaccine in pregnancy — Clalit Health Services study