Timely Progestin Lowers Risk for Preterm Birth

Norra MacReady

December 10, 2013

Early initiation of progesterone prophylaxis is associated with a reduction in spontaneous preterm births among women with a history of preterm delivery, a new retrospective cohort study shows.

However, special efforts to promote timely access to care and initiation of progesterone treatment are likely needed to lower the rate of prematurity, write Kara B. Markham, MD, from the Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, The Ohio State University, Columbus, and colleagues in an article published online December 6 in Obstetrics & Gynecology.

The greatest reductions in preterm deliveries were observed in birth rates before 37 and 35 weeks of gestation. No significant difference was seen in the odds of birth at less than 32 weeks' gestation, although the study was not statistically powered to detect a difference at that point in pregnancy.

Our report suggests that progestin prophylaxis can reduce the rate of recurrent spontaneous preterm birth when barriers to care and treatment are aggressively removed and that the gestational age at initiation may affect the success of progestin prophylaxis," the authors write.

The investigators analyzed data on women with a history of preterm birth attending the Prematurity Clinic at The Ohio State University Wexner Medical Center between January 1, 1998, and June 30, 2012. Clinicians started in 2004 to offer high-risk women routine progestin prophylaxis, delivered as weekly injections provided by a clinic staff member, and, starting in 2008, women could opt for daily, self-administered vaginal suppositories. Also in 2008, the clinic started a program designed to identify and address obstacles to the timely initiation of progestin therapy, such as delayed entry to prenatal care, late identification of patients most in need of progestin prophylaxis, barriers to obtaining insurance, and safe administration of progestin injections.

For example, initial clinic appointments "were scheduled at 10–14 weeks of gestation instead of 14–16 weeks of gestation to accelerate the process of obtaining insurance coverage and approval for progestin therapy," the authors write. "This was a major obstacle because Ohio does not yet have presumptive eligibility for Medicaid coverage of prenatal care. Prematurity clinic staff worked with the medical and women's health directors of managed care and fee-for-service Medicaid services to accelerate approvals and initiation of progestin prophylaxis."

As a result of these efforts, the mean gestational age at the first clinic visit dropped from 19.6 weeks in 1998 to 2003, to 17.4 weeks in 2004 to 2008, and to 15.5 weeks after 2008 (P < .01 for trend).

To determine the effect of the program, the authors compared premature birth rates between 1998-2003, 2004-2007, and 2008-2012. The comparison includes 1066 women, all with a history of 1 or more preterm deliveries.

Table. Preterm Births by Period

Gestational Period 1998-2003 (N = 338) 2004-2007 (N = 313) 2008-2012 (N = 401) P (for Trend)
Less than 37 weeks 144 (42.6%) 156 (49.8%) 159 (39.6%) .02
Less than 35 weeks 85 (25.2%) 97 (31%) 87 (21.6%) .017
Less than 32 weeks 33 (9.8%) 48 (15.3%) 58 (14.4%) .072

Compared with the period from 1998 to 2007, the odds ratios of preterm birth in 2008-2012, adjusted for race, cerclage, smoking, and number of prior preterm births, were 0.75 at less than 37 weeks' gestation (95% confidence interval [CI], 0.58 - 0.97), 0.70 at less than 35 weeks' gestation (95% CI, 0.52 - 0.94), and 1.21 at less than 32 weeks' gestation (95% CI, 0.83 - 1.76).

It is possible that some unidentified factor may be responsible for the decrease in births before 37 and 35 weeks' gestation after 2008, but demographic composition of the clinic population remained the same, and no other major changes in the obstetric care protocol were introduced.

"Thus," the authors conclude, "we are left with the introduction of a more aggressive appointment process that facilitated elimination of barriers to early initiation of progestin as the likely explanation for our findings." They suggest that women at highest risk for delivering early may best be served in a clinic staffed by specialists in maternal-fetal medicine and an aggressive program that facilitates prompt initiation of progestin treatment.

The authors have disclosed no relevant financial relationships.

Obstet Gynecol. Published online December 6, 2013. Abstract


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