Officials at the Centers for Disease Control and Prevention reported that they are aware of at least nine cases of laboratory-confirmed Zika virus infection in pregnant travelers, and that in four of these cases, fetuses were either spontaneously lost or aborted.

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, according to the CDC’s latest Morbidity and Mortality Weekly Report ( 2016 Feb 26. doi: ).

The agency is also investigating reports of 10 other cases of pregnant women with possible Zika virus infection.

Of the nine confirmed cases, six women were infected with Zika virus in their first trimester. In two cases, the pregnancies were terminated and two of the pregnancies resulted in stillbirths. Another woman gave birth to an infant with microcephaly, and one woman is still pregnant and has not experienced any complications so far.

Two of the nine women became infected with Zika virus during their second trimesters, one of whom has delivered a healthy infant and the other of whom is still pregnant with no known complications thus far. The last of the nine women, who became infected during her third trimester, gave birth to a healthy infant with no known complications.

There were no Zika virus–related hospitalizations or deaths among the nine women with Zika virus.

“To better understand the effects of Zika virus infection during pregnancy, CDC has established the U.S. Pregnancy Registry for Zika Virus Infection,” announced Dr. Denise J. Jamieson , colead of the Pregnancy and Birth Defects Team at the CDC. “This registry will provide information about the effects of Zika virus on pregnant women and their children.”

Participation in the registry is voluntary and information will be available on the CDC website soon, Dr. Jamieson added. Until then, the CDC maintains a 24/7 consultation hotline for both pregnant women and health care providers concerned about Zika virus infections, at 1-800-CDC-INFO. Patients and providers can also email .

Additionally, CDC officials stated that they have received reports of at least 14 instances in which Zika virus may have been transmitted between individuals through sexual contact. Two of these cases are confirmed to have been transmitted to women from men who visited a Zika-endemic area, while another four are “probable cases” of sexual transmission, and another six are under investigation. Two reported cases were excluded after receiving additional information.

“Men who reside in or have traveled to an area of ongoing Zika virus transmission and have a pregnant partner should abstain from sexual activity or consistently and correctly use condoms during sex with their pregnant partner for the duration of the pregnancy,” said the CDC in a statement ( MMWR. 2016 Feb 26. doi: ).

The World Health Organization also released a new situation report on Zika virus, microcephaly, and Guillain-Barré syndrome, saying that although Zika virus has been spreading to more geographic areas since the beginning of the crisis, cases of microcephaly and neonatal malformations are increasing only in Brazil and French Polynesia.

Additionally, the WHO released interim guidelines on psychosocial support for pregnant women who may be infected with Zika virus and families dealing with an infant born with either microcephaly or another neurologic disorder.

At a press briefing on Feb. 26, CDC Director Dr. Tom Frieden , noted that it has been 6 weeks since the CDC issued its first travel warning regarding Zika virus, and that the agency is “learning more about Zika everyday.” He added that the current state of the Zika virus outbreak is an “unprecedented situation.”

But Dr. Frieden also stressed that the exact link between Zika virus infection and microcephaly is still unknown, and it is not clear at what stage in the pregnancy Zika virus affects the fetus.

It’s also unknown whether infants born to mothers with Zika virus infection who don’t develop microcephaly will have any other health problems in the future. “Unfortunately, this is something we may not know for many years,” Dr. Frieden said.