The World Health Organization on Friday changed its advice for pregnant women considering a Covid-19 vaccine, abandoning language opposing immunization for most expectant mothers unless they were at high risk.
The new wording followed an outcry to the W.H.O.’s guidance for pregnant women. It still “recommends not to use” the vaccines for pregnant women unless the women are at high risk because of potential exposures or underlying health conditions.
Several experts had expressed disappointment on Thursday with the W.H.O.’s position. The experts noted that it was inconsistent with guidance on the same issue from the U.S. Centers for Disease Control and Prevention, and would confuse pregnant women looking for clear advice.
An earlier version of this article stated that the W.H.O. had changed its guidance. Organization officials have since pointed out that the guidance has not been altered in the recommendations for these individual vaccines.
But a new section in a document detailing features of the vaccines now does not explicitly recommend against using them. It now reflects their safety profile: “Based on what we know about this kind of vaccine, we don’t have any specific reason to believe there will be specific risks that would outweigh the benefits of vaccination for pregnant women.”
The new advice is now closely aligned with the C.D.C.’s position.
The vaccines made by Pfizer-BioNTech and Moderna, while they have not been tested in pregnant women, have not shown any harmful effects in animal studies. And the technology used in the vaccines is generally known to be safe, experts said.
Experts praised the shift, welcoming agreement between the world’s leading public health organizations on this important issue.
Dr. Denise Jamieson, an obstetrician at Emory University and a member of the Covid expert group with the American College of Obstetrics and Gynecology, said she was pleased to see the new advice. The association was among the many women’s health organizations that had urged Pfizer and Moderna to speed up vaccine tests in pregnant women.
“The more permissive W.H.O. language provides an important opportunity for pregnant women to get vaccinated and protect themselves from the severe risks of Covid-19,” Dr. Jamieson said. “This impressively rapid revision by W.H.O. is good news for pregnant women and their babies.”
Pregnant women have traditionally been excluded from clinical trials, leaving a dearth of scientific data on the safety of drugs and vaccines in women and their unborn children. Vaccines are generally considered to be safe, and pregnant women have been urged to be immunized for influenza and other diseases since the 1960s, even in the absence of rigorous clinical trials to test them.
Pfizer will test its vaccine in pregnant women over the next few months, according to a spokeswoman for the company. And Moderna plans to establish a registry to observe side effects in women who were immunized with its vaccine.