MTNR1B and gestational diabetes: A potential interaction between the pre-pregnancy body mass index (BMI) and the MTNR1B rs10830963/G risk allele was suggested previously by a meta-analysis of case-control genetic studies, which indicated that the effect of carrying the MTNR1B rs10830963/G allele became significant on GDM development only in studies with patients with mean pre-pregnancy BMI values above 25 kg/m2 [12].