A majority of the women who contracted Zika in the first or second trimester were still pregnant at the time of the report in early April. Other research has found that pregnant women infected with the Zika virus during their first trimester face as high as a 13 percent chance that their fetus will develop microcephaly. Dr. Stella Guerra performs physical therapy on an infant born with microcephaly on June 2, in Recife, Brazil. (Mario Tama/Getty Images)