Human metapneumovirus infection in pregnancy: A systematic review of cohort studies and case reports

BACKGROUND: Human metapneumovirus (hMPV) is an important cause of acute respiratory tract infection worldwide, but its impact during pregnancy has not been systematically characterized. AIM: To synthesize available evidence on maternal, obstetric and neonatal outcomes of hMPV infection in pregnancy. METHODS: Following PRISMA 2020 guidelines, a comprehensive search of PubMed/MEDLINE, EMBASE, Scopus, Web of Science and Google Scholar from inception to November 2025 identified studies reporting laboratory-confirmed hMPV infection in pregnant women. Eligible designs included case reports, case series and observational studies; however, the available evidence consisted predominantly of case reports and small case series, with only two prospective cohort studies contributing population-level data. Given anticipated heterogeneity, findings were synthesized narratively. RESULTS: Seven studies met inclusion criteria, comprising two prospective community-based cohorts and five case reports/series. Across studies, approximately 50-60 women had laboratory-confirmed antenatal hMPV infection after exclusion of postpartum-only cases and accounting for non-overlapping cohorts. In community cohorts from Nepal and Thailand, hMPV accounted for a modest but non-trivial proportion of symptomatic antenatal respiratory illnesses, most of which were mild to moderate, self-limited, and did not require hospitalization or intensive care. In contrast, case-based reports described severe pneumonia and acute respiratory distress syndrome (ARDS) in women-typically in the second or third trimester-with underlying comorbidities such as asthma, morbid obesity, diabetes, chronic kidney disease or hypertensive disorders; no maternal deaths were reported. Obstetric outcomes were generally reassuring, although one cohort demonstrated an increased risk of small-for-gestational-age infants after antenatal hMPV infection, while evidence for preterm birth and other major complications remained limited and inconsistent. Neonatal outcomes were mostly favorable, with live births, gestational age and birthweight distributions comparable to uninfected pregnancies, and no confirmed congenital hMPV infections. CONCLUSION: hMPV is an under-recognized cause of respiratory illness in pregnancy, usually resulting in mild disease but occasionally associated with severe pneumonia and ARDS in women with comorbidities. A possible association with fetal growth restriction has been reported; however, given the predominance of case reports and small cohort data, causality cannot be inferred for obstetric outcomes. Evidence for other adverse maternal and neonatal outcomes remains limited and inconsistent.