In a model adjusted for age and obesity, we detected a statistically significant interaction term between the MTNR1B-rs10830963 polymorphism (additive model) and the number of full-term pregnancies (as continuous), being the estimation for this interaction term: OR: 1.48, 95%CI: 1.01–2.16; p = 0.042, indicating that a higher number of pregnancies in carriers of the G-allele significantly increased the later risk of type-2 diabetes. This evidence concerns the gene MTNR1B and type 2 diabetes mellitus.