Removal of Pregnancy Categories and Likelihood of Prescribing: a Randomized Trial

Objectives: To assess the degree to which removal of FDA' Pregnancy Categories (PC) of medications (A, B, C, and D) from labeling, affects the likelihood that providers will prescribe those medications.

Methods: Over a one-year period a convenience sample of providers was recruited into a randomized, survey-based, study. Two versions of the survey were randomly distributed; version 1 presented clinical vignettes, drug information, and PC, while version 2, presented the identical information without the PC. Respondents were asked to estimate their likelihood of prescribing the drug. A mixed linear model was constructed, with likelihood of prescription as the dependent variable, treated as interval-scaled.

Results: Out of 169 surveys given out, 162 (96%) were returned. Simple effects analysis showed that the presence of PC letter significantly affected the decision to prescribe category B (p<0.001) and C drugs (p=0.008) but not the A or D. Participants were significantly less likely to prescribe class B and C drugs when the letters were not available for review. These findings remained significant even when controlling for covariates (p=0.001).

Conclusions: When a PC letter is absent on labeling, physicians were less likely to use category B and C drugs, the most common medications prescribed in pregnancy.