Dispensing of clomiphene citrate to treat infertility: medication supplied and population prevalence of assisted pregnancies and multiple births.

OBJECTIVE

To determine the proportion of pregnancies resulting in birth that were conceived with the use of clomiphene citrate (CC) and the frequency of multiple pregnancy.

DESIGN

Whole-of-population cohort study, constructed through data linkage. Comprehensive Australian Government records of dispensed medications were linked to state Perinatal Registry records for all births of at least 20 weeks' gestation.

SETTING

The state of South Australia.

PATIENT(S): Women who maintained pregnancy for at least 20 weeks and gave birth between July 2003 and December 2015, a total of 150,713 women with 241,561 pregnancies.

INTERVENTION(S): Not applicable.

MAIN OUTCOME MEASURE(S): Ongoing pregnancy occurring in proximity to CC, defined as dispensing from 90 days before to the end of a conception window derived from newborn date of birth and gestational age.

RESULT(S): Linkage to dispensed prescription records was achieved for 97.9% of women. Women who conceived with CC tended to be older and socioeconomically advantaged and more likely than other women to have a history of miscarriage. Ongoing pregnancies associated with CC comprised 1.6% of the total; 5.7% were multiple births (mostly twins, 94.6%) compared with 1.5% in the remainder (98.5% twins).

CONCLUSION(S): In South Australia, 1.6% of pregnancies (1 in 60) of at least 20 weeks' gestation were conceived proximal to CC dispensing. Of these, 5.7% were multiple pregnancies. This takes the proportion of women who achieved an ongoing pregnancy with medical assistance from 4.4%, based on reports from assisted reproductive technology clinics, to 6% in total.