Early pregnancy outcomes following COVID-19 vaccination and SARS-CoV-2 infection: a national population-based matched cohort study

Abstract

COVID-19 vaccination is effective in reducing the risk of severe SARS-CoV-2 infection in pregnant women,^1,2 but high levels of vaccine hesitancy remain in pregnant populations. In England and Scotland, 59.5% and 63.0%, respectively of women giving birth in January 2022 had received at least one prior dose of COVID-19 vaccination at any point, which was considerably lower than the coverage seen among the general population of reproductive age women at that time.^3–5

Several factors are likely to contribute to COVID-19 vaccine hesitancy in pregnant women, including exclusion of pregnant women from the initial vaccine trials and hence inconsistent guidance early in the vaccination programme reflecting the lack of safety data at that time.⁶ A growing body of evidence suggests that there is no association between COVID-19 vaccination in pregnancy and adverse late pregnancy outcomes, including preterm birth and stillbirth.⁷ There is, in contrast, a paucity of data on early pregnancy outcomes. A recent systematic review identified only two studies, conducted in Norway and the US, comparing the risk of miscarriage between vaccinated and unvaccinated women.⁷ Neither of these case-control studies found evidence of an association between COVID-19 vaccination and miscarriage. In the Norwegian population-based study utilising routine records, women with first-trimester miscarriage had lower odds of having had a COVID-19 vaccination in the preceding five weeks compared with women with ongoing pregnancies (adjusted odds ratio [aOR] = 0.81, 95% CI = 0.69–0.95), and similar odds of having had a vaccination in the preceding three weeks (aOR = 0.91, 95% CI = 0.75–1.10).⁸ In the US study, women with miscarriage had similar odds of having COVID-19 vaccination in the previous four weeks compared with women with ongoing pregnancies (aOR = 1.02, 95% CI = 0.96–1.08).⁹ To our knowledge, there are no published data on the relationship between COVID-19 vaccination and ectopic pregnancy, the other major cause of early pregnancy loss.

There is an urgent need for robust evidence on the safety of COVID-19 vaccines in early pregnancy to inform decision making among women, their healthcare providers, and policymakers. We use population-based pregnancy data from Scotland to investigate whether there was any evidence for an association between COVID-19 vaccination and either miscarriage or ectopic pregnancy. As a secondary objective, we examined whether there was any evidence for an association between SARS-CoV-2 infection and miscarriage or ectopic pregnancy.

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https://doi.org/10.21203/rs.3.rs-1955486/v1