Little was known about the maternal and fetal/infant effects of Zika infection before the 2015 outbreak in the Americas, which made it challenging for public health practitioners and clinicians to care for pregnant women and infants exposed to Zika. In 2016, CDC implemented a rapid surveillance system, the US Zika Pregnancy and Infant Registry, to collect information about the impact of Zika infection during pregnancy and inform the CDC response and clinical guidance.