An umbrella review of maternal pre-pregnancy characteristics and prior cesarean section as risk factors for stillbirth.

BACKGROUND: Stillbirth is the death of a fetus at or after 20 weeks of gestation, making up 60% of perinatal deaths and having significant psychosocial and economic impacts. The present umbrella review assessed maternal risk factors before pregnancy and prior cesarean associated with stillbirth based on meta-analytic studies. MATERIALS AND METHODS: We conducted a search of three major databases until January 2025, focusing on meta-analyses that evaluated environmental risk factors associated with stillbirth. We evaluated the strength of evidence for identified maternal characteristics associated with stillbirth using the validated Ioannidis classification system. We calculated summary effect estimates, 95% confidence intervals (CIs), heterogeneity (I²), 95% prediction intervals, small-study effects, excess significance biases, and sensitivity analyses. To assess the quality of the meta-analyses, we employed the AMSTAR 2 tool. RESULT: This umbrella review included five studies, comprising eight meta-analyses that evaluated 365,158 cases of stillbirth across a total sample size of 70,124,598 participants. Race (black vs. white), chronic hypertension, and maternal age ≥ 35 years showed highly suggestive associations with stillbirth (Class II), while obesity and overweight showed suggestive associations (Class III). Associations for previous cesarean, and pre-existing diabetes were weak (Class IV). Given high heterogeneity and low AMSTAR-2 ratings, these findings should be interpreted as hypothesis-generating rather than causal. CONCLUSION: These results synthesize meta-analytic evidence on maternal characteristics associated with stillbirth. The overall certainty is limited by considerable heterogeneity, and the low/critically low quality of included reviews; therefore, causal inferences are not warranted.