Drug exposure during the periconceptional period: a study of 1793 women.

Background: Many studies have described the prescribing of drugs to pregnant women, but only very few have data concerning the periconceptional period specifically.

Aim: The aim of the study was to evaluate the incidence of exposure to teratogenic drugs during early pregnancy and to determine whether a safer drug exists.

Methods: In a French health insurances database, we analyzed drugs prescribed during the period starting 1 month before and ending 2 months after the beginning of pregnancy between 1 January 2006 and 31 December 2007. Based on the Summary of Product Characteristics (SPC), drugs we considered were those 'contraindicated', 'not recommended', 'to be avoided', and 'possible' for use during the first trimester of pregnancy. For drugs 'contraindicated', we established if there were alternatives with similar efficacy for the mother and lower risk for the fetus.

Results: Over a period of 2.25 years, 8754 drugs were prescribed to 1793 women starting 1 month prior to and ending 2 months after conception. Among these drugs, 20 (0.2%) were 'contraindicated', 195 (2.2%) were 'not recommended', and 1209 (13.8%) were 'to be avoided' during the first trimester of pregnancy. Twenty (1.1%) women received at least one drug that was 'contraindicated' during the first trimester, 171 (9.5%) received a drug that was 'not recommended' and 768 (42.8%) received a drug that was 'to be avoided'. At least one possible alternative was available for all except one 'contraindicated' drug.

Conclusions: During the highest teratogenic risk period, 1.1% of women received a contraindicated drug, despite existence of a safer alternative drug. This may be partly accounted for by physicians not being aware of the pregnancy at the time the drug was administered and could be reduced by adding a section entitled 'women of child-bearing potential' to the SPC.