Adherence rates and outcomes for 17-hydroxyprogesterone caproate use in women with a previous history of preterm birth

Progesterone has been used for preventing preterm birth with mixed results. The American College of Obstetricians and Gynecologists and Society for Maternal-Fetal Medicine recommended the use of 17-hydroxyprogesterone caproate for risk reduction of recurrent spontaneous preterm birth based on the results of a multicenter, randomized trial in the United States. However, recent literature lacks consensus for efficacy in the American population. In addition, partial adherence and outcomes thereof are underreported. Hence, the relationship between practical adherence to 17-hydroxyprogesterone caproate and outcomes were evaluated.

The objective of this study was to evaluate the adherence to 17-hydroxyprogesterone caproate, defined as receipt of greater than 80% of intended injections, at an outpatient maternal-fetal medicine center and its effect on maternal and neonatal outcomes.

This retrospective cohort study included women older than 18 years with a singleton gestation, history of spontaneous preterm birth who initiated 17-hydroxyprogesterone caproate weekly injections between 16 and 20 weeks' gestational age and delivered between the years 2014 and 2017. Women receiving 17-hydroxyprogesterone caproate injections outside of the clinic were excluded. The primary outcome of adherence and secondary outcomes of gestational age at delivery, birthweight, and neonatal outcomes were analyzed using descriptive data, independent t-test, Mann-Whitney U test, chi-square test, and Fisher exact test, where appropriate, with a P value <.05 being considered significant.

Adherence to 17-hydroxyprogesterone caproate occurred in 38 of 92 (41.3%) women included in the study. At baseline, there was a difference in age between groups of adherent and nonadherent women (adherent: 30.8 years; nonadherent: 27.4 years; P=.002). The rate of spontaneous preterm birth less than 37, 35, and 32 weeks were not significantly different in those who were adherent vs nonadherent to 17-hydroxyprogesterone caproate. There were no differences in gestational age at delivery (adherent: 36.8±2.6 weeks; nonadherent: 36.5±3.8 weeks; P=.66), birthweight (adherent: 2776 g; nonadherent: 2709 g; P=.68), or composite neonatal morbidity (adherent: 18.4%; nonadherent: 20.4%; P=.86) between the adherent and nonadherent groups. Neonatal intensive care unit length of stay was 15.5 days in the adherent group compared with 15 days in the nonadherent group (P=.72).

Real-world adherence to 17-hydroxyprogesterone caproate is suboptimal with less than half of women adherent to in-clinic administration. Adherence to 17-hydroxyprogesterone caproate was not associated with a difference in gestational age at delivery or birthweight compared with nonadherence. Further studies are needed to assess the outpatient administration and benefit of 17-hydroxyprogesterone caproate therapy.