Objective. To describe ethnic disparities in the risk of spontaneous preterm birth and related adverse neonatal outcome. Design. Nationwide prospective cohort study. Setting. The Netherlands, 1999–2007. Population. Nine hundred and sixty-nine thousand, four hundred and ninety-one singleton pregnancies with a spontaneous onset of labor. Methods. We investigated ethnic disparities in perinatal outcome for European white, African, South-Asian, Mediterranean and East-Asian women. We performed multivariate logistic regression analyses to calculate the adjusted odds ratio (aOR) and confidence intervals (CIs) of spontaneous preterm birth and the risk of subsequent neonatal morbidity and mortality. Main outcome measures. The primary outcome measure was spontaneous preterm birth before 37 completed weeks of gestation. Secondarily, we investigated subsequent adverse neonatal outcome, which was a composite outcome of intraventricular hemorrhage, bronchopulmonary dysplasia, infant respiratory distress syndrome, neonatal sepsis or neonatal mortality within 28 days after birth. Results. Compared with European whites, the aOR of delivering preterm was 1.33 (95% CI 1.26–1.41) for African women, 1.58 (95% CI 1.47–1.69) for South-Asians, 0.88 (95% CI 0.84–0.91) for Mediterraneans and 1.04 (95% CI 0.98–1.11) for East-Asians. Subsequent odds of adverse neonatal outcome were significantly lower for African (aOR 0.51; 95% CI 0.41–0.64) and Mediterranean women (aOR 0.86; 95% CI 0.75–0.99) when compared with European whites. Conclusions. African and South-Asian women are at higher risk for preterm birth than European white women. However, the harmful effect of preterm birth on neonatal outcome is less severe for these women.