Mothers and their newborn babies in the United States fare relatively poorly, with infant mortality rates and maternal death rates comparable to those in countries like Serbia and Belarus, according to a new study, NBC News reported. Hurt by huge differences in survival between rich and poor mothers, the U.S. fell two spots to No. 33 on the Mother's Index, a ranking from the nonprofit Save the Children that measures the best and worst places in the world for mothers. In Washington, D.C., for example, infant mortality is higher than in the capital of any other wealthy nation — even though infant mortality rates there are the lowest ever, with 6.6 deaths per 1,000 births.