Risk of preterm birth in maternal influenza or SARS-CoV-2 infection: a systematic review and meta-analysis

BACKGROUND: Influenza is a major threat to global health and is an important cause of respiratory diseases. However, there was a controversy on the impacts of influenza infection on adverse pregnancy outcomes and the infant’s health. This meta-analysis aimed to investigate the impact of maternal influenza infection on preterm birth. METHODS: Five databases, including PubMed, Embase, Cochrane Library, Web of Science, and China National Knowledge Infrastructure (CNKI) were searched for eligible studies on December 29, 2022. The Newcastle-Ottawa Scale (NOS) was used to assess the included quality of the included studies. As for the incidence of preterm birth, odds ratios (OR) and 95% confidence intervals (CIs) were pooled, and the results of the current meta-analysis were displayed in forest plots. Subgroup analyses based on similarity in different aspects were conducted for further analysis. A funnel plot was used to assess the publication bias. All of the above data analyses were performed using STATA SE 16.0 software. RESULTS: A total of 24 studies involving 24,760,890 patients were included in this meta-analysis. Through the analysis, we found that maternal influenza infection significantly increased the risk of preterm birth (OR =1.52, 95% CI: 1.18 to 1.97, I(2)=97.35%, P=0.00). After subgroup analysis based on different types of influenzas, we found that women infected with influenza A and B (OR =2.05, 95% CI: 1.26 to 3.32, I(2)=96.14%, P<0.1), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (OR =2.16, 95% CI: 1.75 to 2.66, I(2)=0.00%, P<0.1) in pregnancy were at an increased risk of preterm birth, while those infected with influenza A alone or seasonal influenza were not (P>0.1). CONCLUSIONS: Women should take active steps to avoid influenza infection during pregnancy, especially influenza A and B and SARS-CoV-2, to reduce the possibility of preterm birth.