Do socioeconomic and healthcare indicators account for the high preterm birth rate in the United States? A comparison with France

Context: The United States has higher rates of preterm birth than France. We examined if differences in the socio-demographic characteristics of pregnant women and the use of medical interventions at birth may have contributed to this excess. Methods: Our study included live singleton births in 1995, 1998 and 2003 from the French National Perinatal Sample Survey (n=39,656) and from US birth certificates (n=10,026,891). Preterm birth (< 37 weeks gestation) was based on clinical estimates. We analyzed maternal risk factors (age <20 and >=35, nulliparous and high parity, unmarried, low educational attainment, race (US)/nationality (France), late prenatal care and smoking) and use of cesarean section and induction of labor. Results: The preterm birth rate was 8.1% in the US and 4.8% in France (OR=1.74 [95% CI 1.67-1.83]). Some risk factors were more prevalent in the US (age <20: 12.3% versus 2.6%, parity 4+: 9.1% versus 2.9%, late first prenatal visit: 16.5% versus 4.5%), but fewer women smoked: 13.5% versus 24.0%. Adjustment for these factors did not explain the US excess risk (1.79 [95% CI 1.71-1.89]). Rates of preterm birth with labor induction or cesarean were 3.4% in the US and 2.2% in France (1.58 [95% CI 1.48-1.69] and of preterm birth without any intervention, 4.7% and 2.6% (1.83 [95% CI 1.72-1.95]). Conclusions: Maternal risk factors and higher rates of obstetrical intervention did not explain differences between the US and France. Future research should explore whether France's social and health policies promote better care during pregnancy and reduce maternal stress.