Health at birth is an important predictor of long-term outcomes, including education, income, and disability. Recent evidence suggests that maternal disadvantage leads to worse health at birth through poor health behaviors; exposure to harmful environmental factors; worse access to medical care, including family planning; and worse underlying maternal health. With increasing inequality, those at the bottom of the distribution now face relatively worse economic conditions, but newborn health among the most disadvantaged has actually improved. The most likely explanation is increasing knowledge about determinants of infant health and how to protect it along with public policies that put this knowledge into practice.