The pandemic is far from over and pregnant women are very much lost in the guidelines of protection on Covid-19 vaccines. Future moms are facing the kind of confusion that has dogged the pandemic from the start: The world’s leading public health organizations — the U.S. Centers for Disease Control and Prevention, and the World Health Organization — are offering contradictory advice.
Neither organization explicitly forbids or encourages immunizing pregnant women. But weighing the same limited studies, they provide different recommendations.
The C.D.C.’s advisory committee urged pregnant women to consult with their doctors before rolling up their sleeves — a decision applauded by several women’s health organizations because it kept decision making in the hands of the expectant mothers.
The W.H.O. recommended that pregnant women not receive the vaccine, unless they were at high risk for Covid because of work exposures or chronic conditions. It issued guidance on the Moderna vaccine on Tuesday, stirring uncertainty among women and doctors on social media. (Earlier this month, it published similar guidance on the Pfizer-BioNTech vaccine.)
Several experts expressed dismay at the W.H.O.’s stance, saying the risks to pregnant women from Covid were far greater than any theoretical harm from the vaccines.
In a statement, the C.D.C. said on Thursday that based on how the Pfizer-BioNTech and Moderna vaccines work, “they are unlikely to pose a specific risk for pregnant women.”
The C.D.C.’s recommendation may make sense for the United States, where women may easily be able to consult with their health care providers, said Joachim Hombach, a health adviser to the W.H.O. on immunizations. But the W.H.O. provides guidance to many low- and middle-income countries where women do not have access to doctors or nurses, he said.
The W.H.O.’s recommendation was also made “in the context of limited supply” of the vaccines, Dr. Hombach said. “I don’t think the language is discouraging, but the language is stating the facts.”
Pfizer did not include pregnant women in its initial clinical trials because it followed the policies outlined by the Food and Drug Administration to first conduct developmental and reproductive toxicity studies, said Jerica Pitts, a spokeswoman for the company. Pfizer and Moderna both provided results from toxicity studies in pregnant rats to the F.D.A. in December.
Pfizer plans to begin a clinical study in pregnant women in the first half of 2021, Ms. Pitts said. Moderna is establishing a registry to record outcomes in pregnant women who receive its vaccine, according to Colleen Hussey, a spokeswoman for the company.
Critics of the companies’ decisions to exclude pregnant women from trials say the reproductive toxicity studies could have been carried out much earlier — as soon as promising vaccine candidates were identified. The companies should have added a protocol to enroll pregnant women once it was clear the vaccines’ benefits outweighed potential harm, Dr. Krubiner said.
“It’s hard to understand why that delay is happening and why it wasn’t initiated sooner,” she said. “The bigger issue is, we’re going to have lost months by the time they start them.”