The FokI polymorphism in vitamin D receptor gene in women with spontaneous preterm birth influences new-born birth weight

Aim: Preterm birth (PTB) is defined as birth of a new-born prior to the completed 37th week of gestation. Prior studies confirmed the association between low levels of vitamin D and increased risk of PTB. Considering that polymorphisms of vitamin D receptor (VDR) gene may modify the effects of vitamin D, several studies investigated the potential association between FokI and ApaI single nucleotide polymorphisms of the VDR gene and PTB in different races. The aim of our study was to evaluate the association between FokI and ApaI polymorphisms of the VDR gene and PTB in European Caucasian women, as well as their effect on clinical characteristics of women with PTB and their new-borns (smoking, family history of PTB, maternal and gestational age at delivery, new-born birth weight). Patients and methods: A case-control study was conducted in 113 women with spontaneous PTB (SPTB ; PTB with intact membranes) and 119 women with term delivery. Genotyping of FokI and ApaI polymorphisms of the VDR gene were performed using polymerase chain reaction and restriction fragment length polymorphism methods. Results: No statistically significant differences were found in the distribution of genotype or allele frequencies of tested polymorphisms between patients and controls. We found a statistically significant effect of FokI polymorphism on new-born birth weight in women with SPTB using two-way ANOVA: Factorial design with Scheffe test (F=4.53, P=0.013), with the lowest birth weight identified in mothers carrying the FokI TT genotype (P=0.021). There was no statistically significant interaction between the FokI and ApaI polymorphisms on birth weight. Neither polymorphism was associated with any other clinical characteristic of women with SPTB and their new-borns. Conclusion: We determined that the TT genotype of the VDR FokI polymorphism is associated with new-born birth weight in European Caucasian women with SPTB.