I ran into an interesting review of birth outcomes in biracial couples. Relative risks (relative to white parents) went like this:
WB BW BB
1.2 1.75 2.08 (for low birth weight)
1.17 1.37 1.78 (for preterm birth)
1.42 1.51 1.85 (stillbirths)
Here, WB means a white mother and black father, BW means a black mother and white father. People have looked at the general pattern of higher birth risks in blacks for some time, without much success. Differences in SES, income, education, and amount of prenatal care do not explain it. I wonder why the outcomes are worse in BW couples than WB couples. Could be a hint.