SAN FRANCISCO — If you prescribe 17 α-hydroxyprogesterone caproate to prevent recurrent preterm birth, try to continue the weekly injections to 37 weeks' gestation or delivery, Dr. Andrei Rebarber said at the annual meeting of the Society for Maternal-Fetal Medicine.
Elective discontinuation of 17 α-hydroxyprogesterone caproate (17-OHPC) injections before 32 weeks significantly increased the risk for recurrent preterm birth in 81 women, compared with 400 women who continued injections until delivery or the end of 36 weeks' gestation, reported Dr. Rebarber of Mount Sinai School of Medicine, New York, and his associates.
The design of the landmark study that found 17-OHPC can reduce recurrent preterm birth risk in singleton pregnancies was to continue injections to week 37 or delivery.
The current study, a retrospective analysis of separate data, found that the rate of spontaneous preterm birth before 37 weeks' gestation increased from 33% in the control group to 48% in women who stopped 17-OHPC early.
Preterm births before 35 weeks' gestation increased from 14% in the control group to 31% among early stoppers. Preterm births before 32 weeks increased from 7% in the control group to 16% in the early-cessation group.
The analysis of data from Matria Healthcare Inc., an obstetric services company, also found that women with a history of more than one preterm birth had a nearly threefold higher risk for recurrent preterm delivery, compared with women with just one prior preterm birth, regardless of the duration of 17-OHPC therapy.
The study included singleton pregnancies in women with a prior preterm birth who began 17-OHPC therapy at weeks 16 through 20 of gestation. In the control group, injections continued to delivery or 37 weeks.
The study group consisted of patients who electively stopped 17-OHPC prior to 32 weeks' gestation and who were delivered more than 10 days after the last injection.
Discontinuation of 17-OHPC was considered elective when the injections were stopped for any reason other than hospitalization, imminent delivery, or an acute condition that led to delivery within 10 days.
“We do know from the Matria database that a significant portion of discontinuation was physician induced, which is worrisome given the fact that there [are no] data on the safety of stopping therapy,” Dr. Rebarber said.
Women in the study group were more likely to be unmarried and smokers, were significantly younger, and more commonly had a history of more than one preterm birth.
After controlling for these differences in a primary logistic regression analysis, early cessation of 17-OHPC remained a significant risk factor for recurrent preterm birth.
The combination of early cessation of injections and a history of more than one preterm birth did not compound the risk for recurrent preterm birth, compared with having either risk factor alone, Dr. Rebarber added.
Because the study was not a chart review but a data analysis, it lacked data on maternal race, substance abuse, domestic violence, the definition of preterm birth in prior pregnancies, and other factors that might have affected results but were not recorded in the database, he commented.
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