The New York Times – One in 10 pregnant women in the continental United States with a confirmed Zika infection had a baby with brain damage or other serious birth defects, according to the most comprehensive report to date on American pregnancies during the Zika crisis.
The report, published Tuesday by the Centers for Disease Control and Prevention, also provided more evidence that the risk of birth defects was greater when women were infected in the first trimester of pregnancy. Fifteen percent of women with confirmed Zika infection in the first trimester had babies with birth defects, the report found.
“It’s an important report because it’s a more complete cohort now, so we’re getting a little more information,” said Dr. Roberta DeBiasi, chief of pediatric infectious diseases for the Children’s National Health System in Washington, who was not involved in the study.
“It does answer that the first trimester is the worst,” she said. “But you can’t take away from this, ‘Oh, as long as I’m not infected in the first trimester, it will be fine.’”
The study indicates that almost every state reported at least one woman with a suspected Zika infection in pregnancy. Some of the women were infected by mosquitoes in the continental United States, but all 51 cases of birth defects reported in the study were traced to infections acquired in one of 16 countries or territories in Latin America or the Caribbean, including Puerto Rico.
“The one thing that didn’t exactly surprise me, but sobers me, is that these reports come in from 44 states,” said Dr. Anne Schuchat, acting director of the C.D.C. “This isn’t something that only the docs in Florida need to worry about; clinicians in every state need to know.”
The report found that babies with birth defects were about as likely to be born to infected women who had no Zika symptoms as they were to women with symptoms, like rash or fever. In general, 80 percent of Zika infections do not produce symptoms.
But the report did not resolve the question of whether symptomatic infection in pregnancy is more dangerous to a fetus than asymptomatic infection, experts said. That is because researchers may not have been aware of all the asymptomatic Zika cases: Some women without symptoms may not have gotten tested for Zika, and consequently, their cases would not be reported.
C.D.C. officials also pointed to another possible shortcoming in the data: Despite a C.D.C. recommendation that brain scans be performed on all babies born to women with possible Zika infection, only 25 percent of the babies in the study had brain imaging, so the actual number of impaired infants could be higher.
“I think it is very likely that we are underestimating the birth defects that follow Zika in pregnancy,” Dr. Schuchat said. “Some babies that are born looking pretty much O.K. are eventually diagnosed with some effects of congenital Zika syndrome.”
The report analyzed 1,297 pregnancies reported from Jan. 15 through Dec. 27, 2016, in the 50 states and Washington, D.C. Of those, 972 with laboratory evidence of possible Zika infection were considered “completed,” resulting in 895 live births and 77 losses, a designation that could include stillbirths, miscarriages and abortions.
Birth defects, ranging from the condition of abnormally small heads, known as microcephaly, to neural tube defects and eye malformations, occurred in 5 percent, or 51, of those pregnancies, including 45 live births. Of the 250 cases where the presence of a Zika infection was confirmed with laboratory testing, 10 percent, or 24 pregnancies, resulted in birth defects, the report said.
All but eight of the 51 cases involved severe brain abnormalities such as microcephaly; the others had impairments that included other brain malformations and dysfunction in the central nervous system. Fourteen of the pregnancies were traced to infection in the first trimester, while 28 could have been infected during any trimester. The rest were missing information on the timing of infection.
Dr. Schuchat emphasized the report’s finding that only “one out of four babies who was born had gotten the type of neuroimaging that we recommend.”
Dr. DeBiasi said that even when her hospital’s Zika program had detected probable infection in pregnant women and urged the hospitals where they planned to deliver to perform brain scans, that had sometimes not occurred.
“Even if they look 100 percent beautiful at birth, they all need to get an ultrasound of the head,” Dr. DeBiasi said. Since only 25 percent of babies in the report had brain scans, “it’s possible that some of the other 75 percent have problems, too.”