Vitamin D receptor polymorphisms in spontaneous preterm birth: a case-control study

AIM: To evaluate the association between the FokI (rs2228570), ApaI (rs7975232), Bsml (rs1544410), TaqI (rs 731236), and Cdx2 (rs11568820) single nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR) gene and spontaneous preterm birth (SPTB), as well as their effect on clinical characteristics of women with SPTB and their newborns. METHODS: This case-control study enrolled women who gave birth at the Department of Obstetrics and Gynecology, University Medical Center Ljubljana between 2010 to 2019. Cases were 118 women with spontaneous initiation of PTB after natural conception and 119 controls with a term singleton delivery after an uncomplicated pregnancy. The molecular analysis of VDR SNPs employed polymerase chain reaction and restriction fragment length polymorphism. RESULTS: Patients and controls did not significantly differ in the distribution of genotype or allele SNP frequencies. However, the FokI polymorphism had a significant effect on newborn birth weight in women with SPTB but not in controls (F = 5.17, P = 0.007, one-way ANOVA with post-hoc Scheffe test), with newborns of FokI TT carriers having the lowest birth weight (P = 0.011). No other VDR SNP was associated with any other clinical characteristic of women with SPTB and their newborns. CONCLUSION: The TT genotype of the VDR FokI polymorphism is associated with newborn birth weight in women of European origin with SPTB.