A new Nature review reports a 15% decrease in risk of stillbirth for women vaccinated against COVID-19.

This paper is a systematic review and meta-analysis, meaning the authors pooled the data from 23 previously published studies to analyze any trends that appear with a larger data set. This paper covers in total 117,552 vaccinated pregnant women from six countries (Israel, USA, UK, Norway, Qatar, and Canada).

Vaccination was associated with a 15% decrease in the odds of experiencing stillbirth, a finding that reached statistical significance.

Of note, the comparison group in these analyses was not infected unvaccinated pregnant women, but any unvaccinated pregnant women, regardless of whether they contracted COVID-19 during pregnancy or not. This suggests that vaccination has a strong protective effect against stillbirth. The authors highlight a recent report from Scotland (not included in the meta-analysis) that found a perinatal death rate of 22.6 per 1000 births in unvaccinated women infected with COVID-19, compared with zero perinatal deaths in vaccinated women with breakthrough COVID-19 infection.

Other factors were unaffected by vaccination status: miscarriage, fetal anomalies, gestational age at birth, pre-term birth, birth weight, and NICU admission. There was a suggestion from the data that vaccination reduces risk of birth asphyxia (by 71%) and birth before 37 weeks (by 10%), but more data is needed.

This meta-analysis is once again reassuring that COVID-19 vaccines do not increase miscarriage rates and is exciting news about the protective effects of vaccination against stillbirth. Women making decisions about vaccination have yet another piece of data confirming that these vaccines are safe for their babies.

All studies have limitations: the individual studies used in this analysis did not report the trimester in which women were vaccinated, so it did not make any conclusions about the optimum trimester for vaccination. The countries included were all high-income countries, which means that most of the vaccines were mRNA vaccines instead of the viral vector vaccines more commonly available in low-and-middle-income countries (e.g. Sinovac, Sputnik, Sinopharm, Covaxin). Additionally, in high income countries, adverse events for mom and baby are comparatively rare, so it can be hard to pinpoint small changes in the rates caused by vaccines.  Further studies will be needed as vaccine access spreads to low-and-middle-income countries where there are great needs.

This news suggests that pregnant women can continue to be confident that COVID-19 vaccines are safe for them and their babies, and, what’s more—they’re even more protective than initially thought.