From the FDA Drug Label
Pregnancy Teratogenic Effects Pregnancy Category BReproduction studies have been performed in rats, rabbits and mice at doses up to 40 times the normal human dose and have revealed no evidence of impaired fertility or harm to the fetus due to cimetidine. There are, however, no adequate and well-controlled studies in pregnant women Because animal reproductive studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
Cimetidine use during pregnancy should be approached with caution. While animal studies have shown no evidence of impaired fertility or harm to the fetus, there are no adequate and well-controlled studies in pregnant women. Therefore, cimetidine should be used during pregnancy only if clearly needed 1 1.
From the Research
Cimetidine Safety During Pregnancy
- The safety of cimetidine, a histamine H2-receptor antagonist, during pregnancy has been evaluated in several studies 2, 3, 4, 5, 6.
- A study published in the American Journal of Epidemiology in 1999 found that the use of cimetidine during the first trimester of pregnancy was not associated with a major teratogenic risk 2.
- A meta-analysis published in Digestive Diseases and Sciences in 2009 found that H2 blockers, including cimetidine, can be used safely in pregnancy, with no increased risks for spontaneous abortions, preterm delivery, and small for gestational age 3.
- Other studies have investigated the effects of cimetidine on maternal and fetal prolactin secretion during labor 5, and its use as an adjuvant treatment for recurrent respiratory papillomatosis in pregnancy 6.
- A study published in the Journal of Perinatal Medicine in 1985 found that cimetidine crossed the placenta at a maternal/cord blood ratio of 3:1, but was not detected in any of the infants 2 hours after delivery 4.
- Overall, the available evidence suggests that cimetidine is generally safe to use during pregnancy, but larger scale studies are warranted to assess its long-term efficacy and safety 6.