Background
Given the potential hazards of teratogenic medicines, to a fetus exposed in utero, monitoring their use around pregnancy is imperative.

Aim
To measure utilisation of teratogenic medicines (Therapeutic Goods Administration’s category D or X) in women who gave birth in New South Wales, Australia, during pregnancy and the 24 months prior.

Materials and Methods
We used linked population‐based datasets including dispensing and perinatal data for all deliveries in NSW between 2005 and 2012. We included pregnancies among concessional beneficiaries only, with complete ascertainment of dispensing claims. Pre‐pregnancy and during‐pregnancy periods were based on birth dates and gestational age. We determined prevalence of exposure using percent of pregnancies in which women had at least one dispensed teratogenic medicine in three‐month time periods.

Results
The study included 191 588 pregnancies (145 419 women). Prevalence of exposure to D/X medicines anytime during pregnancy was 2.0% (<20 pregnancies category X), decreasing from pre‐pregnancy (3.8–6.0%) to first trimester (1.5%), further decreasing in second and third trimesters (0.8% and 0.6% respectively). We observed large reductions in antibiotic prevalence but only modest reductions for psychotropics and antilipidemic agents (all category D). Our results suggest higher use of potentially teratogenic medicines (category D) than those strictly contraindicated for use (category X), during pregnancy. Overall, use was higher in the first trimester than the rest of pregnancy. The high prevalence of potentially contraindicated psychotropics in all three trimesters may suggest a higher benefit‐to‐risk ratio and warrants future research focusing on the reasons for their prescribing to pregnant women.