Familial aggregation of stillbirth: a pedigree analysis of a matched case control study

Abstract

Objective To determine if stillbirth aggregates in families and quantify its familial risk using extended pedigrees. Design State-wide matched case-control study. Setting Utah, United States. Population Stillbirth cases (n=9 404) and live-birth controls (18 808) between 1978 and 2019. Methods Using the Utah Population Database, a population‐based genealogical resource linked with state fetal death and birth records, we identified high-risk pedigrees with excess familial aggregation of stillbirth using the Familial Standardized Incidence Ratio (FSIR). Stillbirth odds ratio (OR) for first-degree relatives (FDR), second-degree relatives (SDR), and third-degree relatives (TDR) of parents with a stillbirth and live-birth were estimated using logistic regression models. Results We identified 390 high-risk pedigrees with evidence for excess familial aggregation (FSIR≥2.00 and P-value<0.05). FDRs, SDRs and TDRs of affected parents had 1.14-fold (95% confidence interval [CI]: 1.04-1.26), 1.22-fold (95% CI: 1.11-1.33), and 1.15-fold (95% CI: 1.08-1.21) higher stillbirth odds compared to FDRs, SDRs and TDRs of unaffected parents, respectively. Parental sex-specific analyses showed male FDRs, SDRs and TDRs of affected fathers had 1.22-fold (95% CI: 1.02-1.47), 1.38-fold (95% CI: 1.17-1.62), 1.17-fold (95% CI: 1.05-1.30) higher stillbirth odds compared to those of unaffected fathers, respectively. FDRs, SDRs and TDRs of affected mothers had 1.12-fold (95% CI: 0.98-1.28), 1.09-fold (95% CI: 0.96-1.24), and 1.15-fold (95% CI: 1.06-1.24) higher stillbirth odds compared with those of unaffected mothers, respectively. Conclusions We provide evidence for familial aggregation of stillbirth. Our findings warrant investigation into genes associated with stillbirth and underscore the need to design large-scale studies to determine its genetic architecture.