The American health authority CDC recommends that all pregnant and breastfeeding women get vaccinated against the coronavirus.
The authority said that this also applies to women who want to become pregnant soon.
New data from a study with almost 2500 pregnant women showed that vaccinations with the preparations from the manufacturers Moderna or Pfizer / BioNTech before pregnancy or in the first 20 weeks did not lead to a higher risk of miscarriage, it said.
The vaccinations are "safe and effective" and urgently advised in view of the particularly contagious Delta variant of the coronavirus, said CDC boss Rochelle Walensky on Wednesday.
The number of pregnant Covid patients has recently increased, including the number of serious disease courses.
Previous data in connection with the vaccination did not reveal any safety concerns for pregnant women and their babies, the authority said.
"Taken together, these data and the known serious risks of Covid disease during pregnancy show that the benefits of a Covid-19 vaccination for pregnant women are greater than any known or possible risks," it said.
In addition, according to current knowledge, vaccination protection for pregnant women could at least temporarily protect newborns from infection.
The health department had not yet specifically advised pregnant women in the United States to be vaccinated, but had not raised any concerns and presented it as a possibility.
Only recently, an important association of gynecologists and obstetricians (ACOG) advised all pregnant women to be vaccinated.
In Germany, the Standing Vaccination Commission is expected to decide by the end of August whether it would recommend a corona vaccination for pregnant women.
The professional association of gynecologists had spoken out in favor of vaccinating pregnant women.