Can COVID-19 vaccinations cause miscarriage in pregnant women?

The past two years have seen the start of mass vaccination campaigns against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) to contain the coronavirus disease 2019 (COVID-19) pandemic. However, the rapid development and emergency use approval (EUA) of the COVID-19 vaccine has raised concerns about its efficacy, safety and long-term consequences. In particular, pregnant women or those planning a pregnancy are hesitant to get vaccinated.

Study: The risk of miscarriage following vaccination against COVID-19: a systematic review and meta-analysis. Image Credit: Blue Planet Studio/Shutterstock

Background

Initially, pregnant women were excluded from clinical studies aimed at evaluating the effectiveness of Vaccines against covid-19. Therefore, little evidence was available regarding the safety of vaccines during pregnancy. Currently, the majority of health officials have reported that vaccination against COVID-19 is safe for pregnant women. This observation is based on the reduced risk of poor pregnancy outcomes in women vaccinated against COVID-19 compared to unvaccinated pregnant women.

Some studies have indicated the potential risks of cross-reactivity of SARS-CoV-2 spike (S) protein antibodies after mRNA vaccination and human syncytin-1 protein in trophoblastic tissue, which could cause lesions placental. Additionally, autoreactive antibodies against syncytin-1 could lead to early miscarriage. Nevertheless, detailed characterization of protein S structure and amino acid sequencing revealed insignificant homology between protein S antibodies generated after vaccination and syncytin-1, indicating the safety of the COVID-19 vaccine. 19.

About the study

Scientists recently reviewed existing literature to assess miscarriage and live birth rates among pregnant women vaccinated against COVID-19. This review is available in the human reproduction log.

This study obtained all relevant data up to June 2022 from MEDLINE, Cochrane CENTRAL and EMBASE. The authors reviewed all studies related to miscarriages, live births, and ongoing pregnancies in women who received COVID-19 vaccines. Animal studies and those reporting non-clinical results in human participants were excluded.

A total of 505 relevant citations were considered, including randomized controlled trials (RCTs) and observational studies. However, 21 studies meeting all the criteria were selected.

Combining all the studies, pregnancy outcomes in 149,685 women were studied. Participants received one of six COVID-19 vaccines manufactured by Pfizer-BioNTech (mRNA BNT162b2), Moderna (mRNA-1273), Janssen (Ad26.COV2.S), AstraZeneca (ChAdOx1 nCoV184 19), Sinopharm (BBIBP- CorV) and Sinovac (CoronaVac). Overall, the studies considered in this review were at low to moderate risk of bias.

Study results

The average miscarriage rate among pregnant women receiving a COVID-19 vaccine was 9%. The risk of miscarriage among the COVID-19 vaccinated group, compared to the unvaccinated group, showed no significant difference in the miscarriage rate between the two groups. Additionally, both groups had similar rates of ongoing pregnancies or live births.

Boundaries

Heterogeneity in study designs and patient characteristics, as well as risk of bias, limited the generalizability of the current meta-analysis. It also highlights the need for better quality research involving pregnant women in the future. Most studies performed suboptimal protocols, which yielded varied study results. This analysis restricts high-quality evidence. Low-quality evidence also reduced the certainty of pooled estimates, especially for pregnancy outcomes. The incidence of stillbirths and ectopic pregnancies was not reported in any of the studies considered.

Several factors may contribute to overall miscarriage rates during the pandemic, such as mode of conception, ethnicity, and access to maternity services during the lockdown period. The majority of studies were related to the short-term evaluation of the safety of the COVID-19 vaccine. These studies do not offer information about long-term pregnancy outcomes.

Conclusions and future prospects

No apparent high risk of miscarriage was observed in pregnant women who received the COVID-19 vaccine. This rate was consistent with the miscarriage rate in the general population before the COVID-19 pandemic. However, the certainty of this observation is low due to the presence of inconsistencies in the data.

Going forward, there is a need to evaluate the short- and long-term safety and effectiveness of all COVID-19 vaccines on pregnant women and their offspring. In addition, large prospective matched-control cohort studies, as well as epidemiological and translational studies, should be conducted to analyze the efficacy and safety of different COVID-19 vaccination programs, which will help reduce outcomes. maternal and neonatal undesirable.

The authors recommended that future studies follow a standardized reporting system for the primary outcomes, i.e. miscarriage, fertility and pregnancy. This will significantly reduce research waste.