Objective: Approximately 10% of US couples are inter-racial/ethnic. Substantial variation in preterm birth (PTB) rates is seen when stratified by race/ethnicity, although most studies focused solely on maternal racial/ethnic demographics. Our aims were to analyze the contribution of paternal in addition to maternal race/ethnicity, and to evaluate risk of spontaneous PTB for previously understudied inter-racial/ethnic couples.
Methods: California singleton live births from 2007 to 2010 were included. Race/ethnicity was determined based on self-report, obtained from birth certificates and defined as African American (AA), Hispanic, Asian, and White. Logistic regression was used to estimate odds ratios of spontaneous PTB at 20-23, 24-31, 32-36 and <37 weeks of gestation, with White-White couples as reference. Results were stratified by previous PTB, pre-gestational and gestational diabetes and hypertension. To investigate the paternal contribution to the risk for any given maternal race/ethnicity we assessed the rates of PTB among inter-racial/ethnic couples compared to the respective same-race couple. Odds ratios were adjusted for maternal age, parity, BMI, prenatal care, payor status, education and smoking.
Results: Among 1,664,939 live births, 13% (n = 216,417) were born to inter-racial/ethnic couples. Compared to White-White couples, risk for spontaneous PTB was increased across all inter-racial/ethnic couples with a non-White mother, except when the father was Asian. Patterns of association were similar after stratification by previous PTB, hypertension and diabetes. Paternal race/ethnicity was also a significant risk factor for PTB.
Conclusions: Increased risks for spontaneous PTB were seen in most inter-racial/ethnic couple groupings. In addition to maternal race/ethnicity, paternal race/ethnicity was a significant risk factor in many inter-racial/ethnic couplings. Identifying such different risk profiles based on both maternal and paternal race/ethnicity may offer new lines of research inquiry for the underlying etiologies of PTB.
Keywords: Interracial/ethnic couples; paternal race/ethnicity; spontaneous preterm birth.