Obesity is associated with an increased level of inflammation. Interactions between inflammatory and angiogenic pathways are implicated in the major pregnancy disorders. The aim of this study was to investigate whether functional polymorphisms in angiogenesis-regulating genes (VEGFA rs699947, VEGFA rs3025039, KDR rs2071559 and ANGPT1 rs2507800) interact with the maternal BMI to modify the risk of a spontaneous preterm birth (sPTB). We conducted a nested case-control study of 1190 nulliparous Caucasian women (107 sPTBs and 1083 controls). Spontaneous PTB was defined as spontaneous preterm labour or a preterm premature rupture of membranes resulting in a preterm birth at <37 weeks of gestation. DNA was extracted from the peripheral blood and genotyped using the Sequenom MassARRAY system. Among overweight or obese women (BMI ≥25), the VEGFA rs699947 AA genotype was associated with a higher risk of sPTBs [odds ratio (OR) = 2.4, 95% confidence interval (CI): 1.4-4.6, P = 0.001] and a significant interaction between the BMI and the polymorphism was detected (OR = 4.2, 95% CI: 1.7-10.9, P = 0.003). Among women with a BMI <25, ANGPT1 rs2507800 AA genotype was associated with a higher risk of sPTB (OR = 2.3, 95% CI: 1.2-4.4, P= 0.02) and a significant interaction between BMI and the polymorphism was detected (OR = 3.3, 95% CI: 1.1-9.3, P = 0.02). All results remained significant after adjusting for potential confounding factors. The maternal BMI interacts with angiogenesis-regulating gene polymorphisms to modify the risk of sPTBs.