SynthesisBMC pregnancy and childbirth2026
Maternal influenza vaccination during the first trimester of pregnancy and risk for birth defects: an updated systematic review and meta-analysis.
Synthesis in BMC pregnancy and childbirth, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
2 citing papers in PubMed.
- Influenza in Pregnancy: From the Maternal Lung to the Placenta and Fetus.Diagnostics (Basel, Switzerland) · 2026Review
- Vertical Vaccination Against Infant Influenza Hospitalization in a Tropical Setting.JAMA network open · 2026Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
5 authors.
Funding
Abstract
backgroundPregnant people have been recommended to receive influenza vaccine at any stage of pregnancy or before conception. However, a large number of pregnant people do not receive the vaccine because of safety concerns. The aim of this study was to investigate the risk of maternal influenza vaccination during the first trimester for birth defects (BDs).
methodsA literature search of PubMed, Embase, the Cochrane Library, the Web of Science and Scopus databases was performed to identify eligible observational studies published from inception to 28th April 2023. The risk estimates were analyzed by pooling odds ratio (OR) with 95% confidence intervals (CIs). Potential sources of heterogeneity were identified by subgroup and meta-regression analysis. Several categories of sensitivity analyses were performed.
results31 studies involving 1,223,024 individuals were included in this study. Compared with the unvaccinated control group or those receiving influenza vaccination during second or third trimester, no increased risk of total BDs (28 studies, unadjusted OR 1.15, 95% CI 0.97-1.36; 10 studies, adjusted OR 1.03, 95% CI 0.98-1.07) or major BDs (16 studies, unadjusted OR 1.11, 95% CI 0.97-1.25; 6 studies, adjusted OR 1.03, 95% CI 0.98-1.09) was observed among those vaccinated during the first trimester. No potential risks were observed based on different vaccine type, the use of adjuvants, the assessment of BDs or control type. Results were consistent across sensitivity analyses for primary results.
conclusionsThis study provided updated evidence that influenza vaccination in early pregnancy did not increase the risk for BDs.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.