In this small case series, Zika virus infection during pregnancy was associated with a range of outcomes, including early pregnancy losses, congenital microcephaly, and apparently healthy infants. Additional information will be available in the future from a newly established CDC registry for U.S. pregnant women with confirmed Zika virus infection and their infants.

This report provides preliminary information on testing for Zika virus infection of U.S. pregnant women who had traveled to areas with Zika virus transmission. As of February 17, 2016, nine U.S. pregnant travelers with Zika virus infection had been identified. No Zika virus–related hospitalizations or deaths were reported among pregnant women. Pregnancy outcomes included two early pregnancy losses, two elective terminations, and three live births (two apparently healthy infants and one infant with severe microcephaly); two pregnancies (18 weeks’ and 34 weeks’ gestation) are continuing without known complications.

Because of the risk for Zika virus infection and its possible association with adverse pregnancy outcomes, CDC issued a travel alert on January 15, 2016, advising pregnant women to consider postponing travel to areas with ongoing local transmission of Zika virus. CDC also released guidelines for Zika virus testing for pregnant women with a history of travel while pregnant to areas with ongoing Zika virus transmission.

After reports of microcephaly and other adverse pregnancy outcomes in infants of mothers infected with Zika virus during pregnancy, CDC issued a travel alert on January 15, 2016, advising pregnant women to consider postponing travel to areas with active transmission of Zika virus. On January 19, CDC released interim guidelines for U.S. health care providers caring for pregnant women with travel to an affected area (1), and an update was released on February 5 (2). As of February 17, CDC had received reports of nine pregnant travelers with laboratory-confirmed Zika virus disease; 10 additional reports of Zika virus disease among pregnant women are currently under investigation. No Zika virus–related hospitalizations or deaths among pregnant women were reported. Pregnancy outcomes among the nine confirmed cases included two early pregnancy losses, two elective terminations, and three live births (two apparently healthy infants and one infant with severe microcephaly); two pregnancies (approximately 18 weeks’ and 34 weeks’ gestation) are continuing without known complications. Confirmed cases of Zika virus infection were reported among women who had traveled to one or more of the following nine areas with ongoing local transmission of Zika virus: American Samoa, Brazil, El Salvador, Guatemala, Haiti, Honduras, Mexico, Puerto Rico, and Samoa. This report summarizes findings from the nine women with confirmed Zika virus infection during pregnancy, including case reports for four women with various clinical outcomes. U.S. health care providers caring for pregnant women with possible Zika virus exposure during pregnancy should follow CDC guidelines for patient evaluation and management (1,2). Zika virus disease is a nationally notifiable condition. CDC has developed a voluntary registry to collect information about U.S. pregnant women with confirmed Zika virus infection and their infants. Information about the registry is in preparation and will be available on the CDC website.

Zika virus is a mosquito-borne flavivirus that was first isolated from a rhesus monkey in Uganda in 1947 (3). For several decades, only sporadic human disease cases were reported from Africa and Southeast Asia. In 2007, an outbreak was reported on Yap Island, Federated States of Micronesia (3), and outbreaks subsequently were reported from several Pacific Island countries (4). Local transmission of Zika virus was first identified in the Region of the Americas (Americas) in Brazil in May 2015 (5). Since that time, transmission of Zika virus has occurred throughout much of the Americas; as of February 18, a total of 32 countries and territories worldwide have active transmission of Zika virus (http://www.cdc.gov/zika/geo/active-countries.html). Interim guidelines for evaluation and management of pregnant women who have traveled to areas with ongoing local transmission of Zika virus include offering laboratory testing after return from travel (2).

During August 1, 2015–February 10, 2016, CDC received 257 requests for Zika virus testing for pregnant women. Among these requests, 151 (59%) included information indicating that the woman had a clinical illness consistent with Zika virus disease (i.e., two or more of the following signs or symptoms: acute onset of fever, rash, conjunctivitis, or arthralgia). The remaining requests did not document an illness compatible with Zika virus disease, but reporting of symptom information might have been incomplete.

Laboratory confirmation of recent Zika virus infection includes detection of 1) Zika virus, viral RNA, or viral antigen, or 2) Zika virus immunoglobulin M (IgM) antibodies with Zika virus neutralizing antibody titers ≥4-fold higher than neutralizing antibody titers against dengue or other flaviviruses endemic to the region where exposure occurred. Among the 257 pregnant women whose specimens were tested at CDC, 249 (97%) tested negative for recent Zika virus infection and eight (3%) had confirmed Zika virus infection. In addition to the eight patients with laboratory testing performed at CDC, one confirmed case was reported to CDC from a state health department with capacity to test for Zika virus infection.

Among nine pregnant women with confirmed Zika virus disease, no hospitalizations or deaths were reported. All nine women reported at least one of the four most commonly observed symptoms (fever, rash, conjunctivitis, or arthralgia), all women reported rash, and all but one woman had at least two symptoms. Among the six pregnant women with Zika virus disease who reported symptoms during the first trimester, outcomes included two early pregnancy losses, two elective pregnancy terminations, and delivery of a live born infant with microcephaly; one pregnancy is continuing. Among two women with Zika virus infection who had symptoms during the second trimester of pregnancy, one apparently healthy infant has been born and one pregnancy is continuing. One pregnant woman reported symptoms of Zika virus infection in the third trimester of pregnancy, and she delivered a healthy infant.