Ethnic differences in the impact of male fetal gender on the risk of spontaneous preterm birth

Objective To study the impact of fetal gender on the risk of spontaneous preterm birth in various ethnicities. Study design National cohort study in which all singleton live births from 25 +0 weeks onwards without congenital anomalies were included of African, Asian, and Mediterranean women (1999–2010). Our primary outcome measure was preterm birth before 37 weeks. Per ethnic group, male and female neonates were compared. Result In each ethnic group, male fetuses were at increased risk of preterm birth (adjusted odds ratio (aOR) 1.63 for African, aOR 1.71 for Asian, and aOR 1.84 for Mediterranean males). The population-attributable risk of male gender on spontaneous preterm birth is lower in African women (3.9%) than in Asian (10.3%) and Mediterranean women (9.0%). Conclusion Male fetal gender is associated with spontaneous preterm birth in African, Asian, and Mediterranean women, but the total impact of ethnicity on spontaneous preterm birth rate is different.