Concurrent use of hormonal long-acting reversible contraception by women of reproductive age dispensed teratogenic medications, Australia, 2013-2021: a retrospective cohort study

Objectives: To examine patterns in the dispensing of category X medications (Therapeutic Goods Administration categorisation system for prescribing medicines in pregnancy) to women aged 15-49 years in Australia during 2008-2021, and patterns of concurrent use of hormonal long-acting reversible contraception (LARC) and other hormonal contraception.

Study design: Retrospective cohort study; analysis of 10% random sample of national Pharmaceutical Benefits Scheme dispensing data.

Participants, setting: Women aged 15-49 years dispensed category X medications, Australia, 1 January 2013 - 31 December 2021.

Main outcome measures: Incident and prevalent dispensing of category X medications, by medication class, age group, and year; contraceptive overlap (proportions of women dispensed hormonal LARC or other hormonal contraception that overlapped the first dispensing of category X medications), by medication class.

Results: Among 15 627 women aged 15-49 years dispensed category X medications during 2013-2021, the prevalence of dispensing increased from 4.6 in 2013 to 8.7 per 1000 women aged 15-49 years in 2021; the largest increase was for the dispensing of dermatological agents, from 3.9 to 7.9 per 1000 women aged 15-49 years. LARC overlap was inferred for 2059 women at the time of first dispensing of category X medications (13.2%); 3441 had been dispensed any type of hormonal contraception (22.1%). The proportion with LARC overlap was smallest for those dispensed dermatological agents (1806 of 14 331 women, 12.6%); for this drug class, both LARC overlap (adjusted odds ratio [aOR], 0.17; 95% confidence interval [CI], 0.14-0.20) and any hormonal contraception overlap (aOR, 0.28; 95% CI, 0.25-0.32) were less likely for those aged 15-19 years than for women aged 25-29 years.

Conclusions: Concurrent use of highly effective hormonal contraception at the time of first dispensing of category X medications is low in Australia, raising concerns about potential fetal harms during unintended pregnancies. Awareness of the importance of hormonal contraception and its uptake by women prescribed category X medications should be increased.