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.’”