Risk Factors for Adverse Pregnancy Outcomes in Reduced Fetal Movement: An IPD Meta-Analysis.

Abstract

Women experiencing reduced fetal movements (RFM) have an increased risk of adverse pregnancy outcomes (APO). This study aimed to identify factors most associated with APO in RFM pregnancies. Individual participant data meta-analysis (IPD-MA). Multiple maternity units across the UK. 1175 singleton pregnancies with RFM between 28⁺⁰ and 41⁺⁰ weeks' gestation from four prospective cohorts and two randomised controlled trials (RCTs). Factors associated with APO were assessed using two-stage IPD-MA. A composite adverse pregnancy outcome, including: adjusted Odds Ratio, stillbirth, fetal growth restriction (FGR, birthweight ≤ 3rd centile) and neonatal intensive care unit (NICU) admission. APO occurred in 7.7% of RFM pregnancies, with FGR being the most common complication (4.6%). The strongest associations with APO were observed for abnormal fetal heart rate (adjusted Odds Ratio (aOR) = 3.65, 95% CI: 1.84-7.23), cigarette smoking (aOR = 2.96, 95% CI: 1.36-6.44) and maternal past medical history (aOR = 2.35, 95% CI: 1.14-4.82). Lower estimated fetal weight (EFW) centile was also significantly associated with APO (aOR = 0.97, 95% CI: 0.95-0.99), though substantial heterogeneity was present between studies (I² = 80.74%, Q-statistic: p < 0.001). IPD-MA enabled the synthesis of individual-level data across studies, allowing for more accurate and reliable associations by accounting for heterogeneity. Further work is required to investigate the model's generalisability across diverse populations.