Prescription medicines with potential for foetal harm: dispensing before and during pregnancy in New Zealand, 2005-2015.

Purpose: This study describes dispensing of potentially teratogenic prescription medicines before and during pregnancy in New Zealand over the period 2005-2015.

Methods: Records in a national dispensing database were linked with the members of the New Zealand Pregnancy Cohort to determine the proportion of pregnancies with at least one dispensing of a Category D or X medicine, using the Australian pregnancy risk categorisation system. Exposure was examined from 270 days prior to conception through to the end of pregnancy. Pregnancy outcomes of D/X-exposed pregnancies were reviewed.

Results: In the study, 874,884 pregnancies were included. Overall, Category D and X medicines were dispensed during 4.3% and 0.058% of pregnancies, respectively. After excluding misoprostol, X exposure decreased to 0.035%. Generally, dispensing declined through the 270-day pre-pregnancy period and continued to decline throughout pregnancy. Dispensing of X medicines increased over the study timeframe, whereas dispensing of D medicines increased from 2005 to 2011 then declined slightly. Smokers were more likely than non-smokers to have been dispensed a D/X medicine, and compared with European women, Māori and Pacific women were less likely to have been dispensed a D/X medicine. Excluding misoprostol, pregnancies exposed to an X medicine were more likely than D/X-unexposed pregnancies to have ended in termination.

Conclusion: Dispensing of potentially harmful medicines in pregnancy in New Zealand was low, particularly for Category X medicines. However, exposure did increase over the study timeframe. The inclusion of pregnancies that did not progress past early pregnancy better reflects population-level pregnancy exposure to potentially teratogenic medicines.