Researchers measured the impact of maternal syphilis on pregnancy outcome in the Mwanza Region of Tanzania. Women with high-titer active syphilis were at the greatest risk of having low-birth-weight or preterm live births, compared with women with other serological stages of syphilis. Among unscreened women, 51 percent of stillbirths, 24 percent of preterm live births, and 17 percent of all adverse pregnancy outcomes were attributable to maternal syphilis.