WHO's guidance is that the vaccine is safe for everyone - sick, pregnant or otherwise - though curiously not those under 18.

"The vaccine is safe and effective in people with known medical conditions associated with increased risk of severe disease, such as hypertension, diabetes, asthma, pulmonary, liver or kidney disease, as well as chronic infections that are stable and controlled.

Although further studies are required for immunocompromised persons, people in this category who are part of a group recommended for vaccination may be vaccinated after receiving information and counselling.

While pregnancy puts women at higher risk of severe COVID-19, very little data are available to assess vaccine safety in pregnancy.

Nevertheless, 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 vaccine should not be administered to persons younger than 18 years of age pending the results of further studies."

At the bottom WHO offers a disclaimer:

"We do not know whether the vaccine will prevent infection and protect against onward transmission. Immunity persists for several months, but the full duration is not yet known. These important questions are being studied."

https://www.who.int/news-room/feature-stories/detail/the-moderna-covid-19-mrna-1273-vac...

Given the survival rate for women under 50 who contract Covid, who are the only ones who will be pregnant, is, according to the CDC, 99.98%, why on earth would you advise pregnant women to take an experimental biological agent for which "very little data are available to assess vaccine safety in pregnancy"?