Single-nucleotide polymorphisms in genes involved in placental function and unexplained stillbirth

Objective The purpose of this study was to evaluate the association between unexplained stillbirth (SB) and single-nucleotide polymorphisms (SNPs) in genes involved in placental function using a well-characterized cohort. Study Design Placentas were obtained from 50 unexplained SB and 46 live birth controls. Classification of stillbirth was by Wigglesworth criteria. SBs were stratified by weight: appropriate (AGA-SB) and small for gestational age (SGA-SB, less than the 10th percentile) and gestational age: before 32 and after 32 weeks. Placental DNA was extracted and various SNPs in the endothelial nitric oxide synthase (eNOS), Klotho, hypoxic inducible factor-1α, and and tumor necrosis factor-α genes were evaluated. Results None of the SNPs were associated with SB overall. Significantly different genotype distribution emerged for eNOS-SNP rs1800783 when comparing AGA-SB with SGA-SB and control ( P = .004). Its allele-A was more frequent in AGA-SB compared with both controls ( P = .03) and SGA-SB ( P = .001). No differences were seen accordingly to gestational age. Conclusion Unexplained stillbirth in the setting of adequate growth is associated with carrier of allele A of rs1800783 eNOS gene in the placenta.