One of the largest reports on COVID-19 vaccination in pregnancy bolsters evidence that it is safe, although researchers admit more comprehensive research is needed.

The preliminary results are based on reports from over 35,000 U.S. women, age 16 to 54, who received either Moderna or Pfizer shots while pregnant.

The study looked at vaccinations between mid-December 2020 and late-February 2021.

Johnson & Johnson’s vaccine wasn't available at the time of the study and wasn't included in the research. The company said in early April they were in "discussions with health authorities" to start studies in pregnant women and children of the single-shot COVID-19 vaccine "in the near future."

The rates of miscarriage, premature births and other complications in women who received the vaccine were comparable to those observed in published reports on pregnant women before the pandemic.

Researchers did find pregnant women were more likely to report injection-site pain compared to nonpregnant women. However, pregnant women reported fewer cases of headache, muscle aches, chills or fever than nonpregnant women who received a vaccination.

The new evidence from researchers at the Centers for Disease Control and Prevention was published Wednesday in the New England Journal of Medicine.