Biracial couples and adverse birth outcomes: a systematic review and meta-analyses

Background. Differences in birth outcomes such as low birthweight (LBW), preterm births (PTB), stillbirth, differences in birthweight in Black vs. White race are well known. Infants born to biracial parents (mother and father from either Black or White races) also experience higher adverse birth outcomes. Objective. To systematically review and meta-analyze birth outcomes among parents of mixed racial background compared to parents of same race. Search strategy. Medline, Embase, CINAHL and bibliographies of identified articles were searched for English language studies. Selection criteria. Studies reporting association between parental mixed racial status and LBW, PTB, or small-for-gestational age (SGA) outcomes were included. Data collection and analyses. After exclusion of duplicate cohorts in different publications, data from White mother-Black father (WMBF), Black mother-White father (BMWF) and Black mother-Black father (BMBF) groups were compared with the White mother-White father (WMWF) group. Results. Eight English language studies from of 26?335?596 singleton births were included and reviewed. Compared to the WMWF group, the adjusted odds ratio (95% confidence intervals) were: (a) low birthweight; 1.21 (1.10-1.33) for WMBF, 1.75(1.64-1.87) for BMWF, and 2.08 (1.81-2.38) for BMBF; (b) preterm births; 1.17 (1.05-1.31) for WMBF, 1.37 (1.18-1.59) for BMWF, and 1.78 (1.59-2.00) for BMBF; and (c) stillbirths; 1.43 (0.92-2.21) for WMBF, 1.51 (1.09-2.08) for BMWF, and 1.85 (1.47-2.32) for BMBF. Conclusion. Biracial status of parents was associated with higher risk for adverse pregnancy outcomes than both White parents but lower than both Black parents, with maternal race having a greater influence than paternal race on pregnancy outcomes.