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.