5% of U.S. Pregnant Women With Zika Had Baby With a Birth Defect
Five percent of pregnant women with a confirmed Zika infection in the United States territories, including Puerto Rico, went on to have a baby with a related birth defect, according to the most comprehensive report to date from federal officials.
The report, published on Thursday by the Centers for Disease Control and Prevention, also provided for the first time preliminary estimates of this risk by trimester. Previously, there were not enough births following exposure to the Zika virus to make such estimates.
This new report reviewed nearly 2,550 cases of women with possible Zika virus infection who completed pregnancies — meaning they gave birth, miscarried or experienced stillbirth — from Jan. 1, 2016 to April 25, 2017.
Roughly 1,500 of those women had Zika infection actually confirmed by laboratory testing.
Eight percent of offspring of pregnant women in U.S. territories with a positive nucleic acid test for Zika infection in the first trimester had birth defects linked to the virus. By contrast, 5 percent of these infants did when infection occurred in the second trimester, and 4 percent in the third trimester.
“It’s incredibly useful,” said Dr. Laura Riley, a specialist in high-risk pregnancies and infectious disease at Massachusetts General Hospital.
“Patients want to know what is the likelihood their baby could be damaged. At least now, I feel like I had some numbers I can utilize in counseling.”
C.D.C. researchers classified cases by the trimester in which the laboratory test was conducted or symptoms were reported, said Peggy Honein, the chief of the birth defects branch at the C.D.C. That “may not represent the precise timing of infection.”
The data reported to C.D.C. came from the Commonwealth of Puerto Rico, the Federated States of Micronesia, the Republic of Marshall Islands, American Samoa, and the United States Virgin Islands.
In total, the agency counted 122 babies with possible Zika-related birth defects, such as neural tube defects, eye abnormalities or microcephaly, an unusually small head.
Previously, Puerto Rico’s department of health had only reported about 35 cases in which a fetus was lost or baby was born with Zika-related birth defects, raising concerns that the extent of damage to infants has been underplayed on the island.
On a call with reporters, Dr. Anne Schuchat, the acting director of the C.D.C., replied, “We do believe that Puerto Rico authorities are doing a very good job right now in evaluating babies whose mothers had Zika infection, and characterizing them and reporting in.”
On Monday, Puerto Rico declared that its Zika epidemic had ended, based on data showing the number of new cases had fallen. Regardless, C.D.C. officials said today that they still advised pregnant women to avoid traveling to Puerto Rico and to protect themselves against mosquito bites, if they do.
“We do agree that the disease went up and it’s come down, but that the risk is ongoing and that’s why they are continuing intensive surveillance and outreach,” Dr. Schuchat said.
Dr. Tom Frieden, the former director of the C.D.C., said of Zika, “It may not be epidemic anymore, but it’s endemic” in Puerto Rico.
“What we often see with this type of infection, it’s really bad in the first year and less bad in future years,” he added. “That’s why C.D.C. has retained its travel guidance.”
Dr. Frieden also cautioned that this report “is a minimum estimate of the number of infants who may be Zika-affected,” in Puerto Rico, because not all women whose infections were confirmed in the first trimester have given birth yet.
“The report mentions that only 18 percent of pregnancies they identified were in the first trimester, while you’d expect it to be a third,” he said.
Testing pregnant women for Zika will be routine in Puerto Rico, Dr. Schuchat said.
Women who do not have any symptoms of Zika virus still may give birth to a baby with Zika-related birth defects, research has shown. The only way to catch those infections is to screen women because they may have been exposed to Zika-infected mosquitoes or may have had sexual contact with an infected partner.
In this new report, “The presence or absence of symptoms was not predictive of whether a baby would be damaged,” Dr. Riley said. “There were women who had asymptomatic Zika whose babies were damaged.”
Currently, only about 60 percent of babies born alive in United States territories had results of Zika laboratory testing reported to pregnancy and infant registries. It’s important that all babies who may have been affected are monitored, as early intervention can help.
For instance, some babies who appear normal at birth later develop an unusually shrunken head. Only with long-term tracking can health officials get an accurate estimate of the scope of the problem.
Even now, Puerto Ricans often do not take every precaution to avoid Zika infection. In another C.D.C. report released on Thursday, roughly 88 percent of residents with a recent birth said they had used screens on doors to keep mosquitoes at bay.
But 56 percent of roughly 1,800 sexually active pregnant women reported never using condoms to protect themselves from getting Zika from a sexual partner.