Genetic Variants Associated with Placental Abnormalities in Stillbirths

Abstract Background: Placental insufficiency (PI), characterized by impaired placental function, is a leading cause of stillbirth. Although rare coding variants are known to cause a subset of stillbirths, their contribution to PI is poorly understood. Methods: We conducted a secondary analysis of stillbirth cases (N=292) of the Stillbirth Collaborative Research Network study with exome sequencing available on postmortem placental or fetal samples. PI was defined by standardized placental pathological lesions (e.g., maternal vascular malperfusion) and prespecified clinical criteria for placental dysfunction. Candidate gene-based rare-variant burden analysis was performed using the Sequence Kernel Association Test-Optimal framework, focusing on evolutionarily constrained developmental and placental-function genes. Primary analysis compared stillbirths with and without placental vascular malperfusion. Similar comparisons by clinical PI and other placental pathological lesions were conducted in secondary analysis. Results: Stillbirths with PI phenotypes demonstrated different patterns of genetic variation than stillbirths without PI. Specifically, we observed nominal differential enrichment of constrained variants in biologically prioritized placental-function genes, regulating extravillous trophoblast invasion and spiral artery remodeling (CTNND2, PHACTR1, SLIT1, VEGFA), placental angiogenesis (IGF2R, TEK), mitochondrial homeostasis (OPA1), and fetal growth (DLK1, GNAS). Secondary analyses on specific placental pathological lesions suggested recurrent enrichment of genes within similar placental developmental pathways. Conclusions: We observed nominal differential enrichment of constrained developmental and placental-function genes in stillbirths with PI compared to stillbirths without PI. The observed genetic signals across PI phenotypes suggest shared biological pathways underlie placental dysfunction. Our findings advance genotype-phenotype characterization and help prioritize candidate pathways for larger collaborative genomic and functional studies to improve stillbirth risk stratification and prevention.