The objective of the study was to check the effect of the combination of metronidazole and miconazole (M+M) for the prevention of sexually transmitted infections/disorders related preterm delivery/birth. Antiprotozoal vaginal metronidazole was not able to prevent preterm birth, while the antifungal topical miconazole use showed some reduction in preterm birth in our previous studies. The population-based large control (without any defects) data set of the Hungarian Case-Control Surveillance System of Congenital Abnormalities was used for the evaluation of the combination of M+M for birth outcomes. Of 38,151 controls, 846 (2.2%) had treatment with vaginal tablet of M+M for vaginal infections. The prevalence of preterm birth was 9.5% after this treatment compared with the 9.2% of preterm birth in the untreated group. Thus the combination of M+M was not able to reduce the preterm birth associated with vulvovaginal infections/disorders.