Anthropology, University of Oklahoma
April 16, 2020 , Platinum Ballroom
Infant mortality (death before first birthday) is predicted to be influenced by male investment (greater investment reducing risk of infant death) and interbirth interval (IBI) (risk of mortality decreasing as duration since previous live birth increases). This study uses 2014-2015 merged natality and mortality files for 3,946,963 U.S. births (second birth or greater). Infant mortality rate is 5 deaths/1000 births. Mean IBI is 50.0 months. Male commitment is measured by maternal marital status: married (63.2% of births), unmarried with paternity acknowledged (26.0%), and unmarried with paternity not acknowledged (i.e., no father on birth certificate) (10.8%). Male commitment is expected to be highest for married women and lowest for unmarried women without paternity acknowledgment. Logistic regression models that control for maternal sociodemographic factors (age, ethnicity, education, income, BMI) and birth factors (caesarian, premature, birthweight, sex) show higher infant mortality for unmarried women both with (OR=1.08, p<0.001) and without (OR=1.37, p<0.001) paternity acknowledged, relative to married women. IBI has a weak linear relationship with infant mortality (OR=0.998, p<0.001), but a stronger nonlinear relationship when divided into thirds; compared with long IBI (>53 months), increased odds of infant death are associated with short IBI (<=28 months) (OR=1.28, p<0.001) and medium IBI (28 to 53 months) (OR=1.07, p<0.001). Interactions between marital status and IBI were nonsignificant. Infant mortality risk is greater when the father does not acknowledge paternity or when IBI is short. These results advance life history theory by supporting predictions regarding parental investment and tradeoffs between current and future reproduction.