A team of reproductive specialists from Queens Medical Research Institute, Imperial College London and University College London, all in the U.K., has conducted a systematic review and associated meta-analysis of data on pregnant women receiving COVID vaccines. In their paper published in the journal Human Reproduction, the team reports that they found no increased risk of miscarriage by women receiving any of the COVID vaccines.
From the early days of the pandemic, since not long after COVID vaccines were available, there have been concerns regarding possible negative associations in pregnant women who were vaccinated. Such concerns were raised initially because little to no research was conducted on the impact of the vaccine on pregnant women as the vaccine was being rushed to a needy populace. As the pandemic wore on, concerns continued to be voiced regarding possible increased risk of miscarriage.
As time passed, medical scientists noted that the numbers of pregnancies and births worldwide diminished during the pandemic, though it was not known why. Some studies suggested people simply chose not to risk having a baby during a pandemic—others suggested it showed that medical scientists were either not doing their jobs or were outright lying about findings regarding vaccinating pregnant women. In this new effort, the team in the U.K. sought to find the answer to at least one part of the debate—do COVID vaccines increase the risk of miscarriage?
The researchers combed data from EMBASE, MEDLINE and Cochrane CENTRAL, looking at statistics from prior to the onset of the pandemic up through June 2022 and comparing rates of miscarriage between pregnant women who received a COVID vaccine and those who did not. In all, they followed the pregnancies of 149,685 women.
They found an overall average miscarriage rate of 9% for women receiving any of the available vaccines—a rate that is not statistically significant when compared to that of pregnant women who did not receive a vaccine. They also found no significant differences in live birth rates for the same women in the study.
The research team acknowledges that the heterogeneity observed throughout the studies they looked at, along with patient characteristics and risk bias, suggests that some of the data quality was not up to scholarly standards. Thus, they suggest more work is required to corroborate their results.
Michael P Rimmer et al, The risk of miscarriage following COVID-19 vaccination: a systematic review and meta-analysis, Human Reproduction (2023). DOI: 10.1093/humrep/dead036
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