Objective
The purpose of this study was to determine the role of previous term delivery on the rate of recurrent preterm birth in women with previous spontaneous preterm delivery (SPTD) who receive 17-alphahydroxyprogesterone caproate (17P) therapy.
Study Design
Women with singleton gestations who were receiving 17P therapy were studied. Rates of recurrent SPTD were compared for 1 or ≥2 SPTD with and without a previous term delivery.
Results
Five thousand one hundred two women had 1 previous SPTD, and 2217 women had ≥2 SPTDs. In women with 1 previous SPTD, a previous term delivery had lower rates of SPTD at <35 weeks (8.4% vs 11.2%; P = .002) and preterm delivery at <32 weeks (4.7% vs 6.2%; P = .027) compared with those women with no such history. No differences were found for SPTD at <35 weeks with ≥2 SPTDs.
Conclusion
In patients who received 17P therapy with 1 previous SPTD, a previous term delivery confers a reduction in risk of preterm delivery at <37, <35, and <32 weeks’ gestation; such reduction is not evident with ≥2 previous SPTDs.
Preterm birth is the leading cause of neonatal death and morbidity and long-term disability of nonanomalous infants. Previous studies have identified a history of ≥1 previous spontaneous preterm delivery (SPTD) as a risk factor with a high predictive value for recurrence. The risk of recurrent SPTD is also dependent on whether the woman has a history of term delivery. For example, patients with previous SPTD followed by a subsequent term delivery have a lower risk of recurrence compared with those women without an antecedent term delivery.
Recent studies have provided evidence for the efficacy of intramuscular 17 alphahydroxyprogesterone caproate (17P) therapy and vaginal progesterone suppositories to prevent preterm birth in women with a singleton gestation and a history of SPTD. A recent review by Iams and Berghella that addressed care for women with previous preterm birth noted, however, that there are no data directly addressing the benefit of 17P therapy in women with previous term birth followed by a SPTD. The objective of this study was to determine the role of previous term delivery on the rate of recurrent preterm birth in women with previous SPTD who received 17P therapy.
Methods
We performed a retrospective review of deidentified clinical data that had been collected from high-risk pregnant women who were enrolled in a 17P therapy outpatient administration program through Alere Women’s and Children’s Health. Perinatal nurses provided initial patient education in the home that included a review of the signs and symptoms of preterm labor and medication compliance. At the initiation of the 17P therapy outpatient administration program, patients received information concerning informed consent to allow their deidentified personal health information to be used for research and reporting purposes and were asked to sign a consent form if they wished to participate. All patients received weekly home nursing assessments and injections and had telephone perinatal nursing and pharmacist support available to them 24 hours a day 7 days a week for any pregnancy-related concerns. A weekly intramuscular injection of 250 mg of 17P was prescribed from enrollment until either 36 completed weeks or preterm delivery. Unit-dose vials of 17P were delivered to the patients home from a qualified compounding pharmacy.
Clinical data were collected from the patient and her physician throughout provision of outpatient services with the use of standardized definitions, forms, and computer systems and were maintained in a relational database. Records that were identified for inclusion in the present study met the following criteria: women with a singleton pregnancy, a history of at least 1 previous SPTD, initiated 17P therapy at <25 weeks’ gestation, and a documented pregnancy outcome of the current pregnancy.
Maternal characteristics that were evaluated included maternal age, gravidity, prepregnancy body mass index, race, medical insurance status, marital status, smoking, and presence of cervical cerclage. Pregnancy history that included miscarriage, number of previous SPTDs (only 1 or ≥2), and the presence or absence of a previous term delivery were also obtained. We examined data regarding 17P administration that included gestational age at start of injections, number of injections received, and the percentage of women who received the expected injections based on a weekly dosing schedule. Pregnancy outcomes that were evaluated included gestational age at delivery, onset of labor and delivery (spontaneous labor vs medically indicated), and incidence of perinatal death including stillbirth (fetal death at ≥20.0 weeks’ gestation) and neonatal death (within 28 days of delivery). The main outcomes of the study were total rates of preterm delivery at <37 weeks’ gestation and the rates of recurrent SPTD at <37, <35, and <32 weeks’ gestation.
Data were grouped by number of previous SPTDs (1 previous SPTD or ≥2 SPTDs). Within each previous SPTD group (1 previous SPTD or ≥2 SPTD) maternal characteristics, 17P administration, and pregnancy outcomes were compared for women with and without a history of at least 1 term delivery. The results are expressed as mean ± standard deviation, median, or odds ratio with 95% confidence intervals. Univariate analyses included the use of χ 2 , Student t , and Mann-Whitney U test statistics. For the logistic regression models, we adjusted for those variables that had a probability value of < .1 in the univariate analyses. For all analyses, 2-sided probability values of < .05 were considered statistically significant. The institutional review board of Central Baptist Hospital approved the analysis of this data.
Results
A total of 5102 patients had 1 previous SPTD, and 2217 patients had ≥2 SPTDs. Results are presented by the number of previous SPTDs per group (1 or ≥2).
Women with 1 previous SPTD with or without previous term delivery
Maternal characteristics for this group of women are listed in Table 1 . Compared with women without previous term delivery, those with a previous term delivery had higher maternal age ( P = .004), a higher rate of a history of miscarriage ( P < .001), a higher rate of obese women ( P = .029), a higher rate of being unmarried ( P < .001), a higher rate of black race ( P < .001), and a higher rate of smoking ( P < .001).
| Variable | History of term delivery | P value | Odds ratio (95% CI) | |
|---|---|---|---|---|
| Yes (n = 1579) | No (n = 3523) | |||
| Mean maternal age, y a | 30.7 ± 5.2 | 30.1 ± 5.6 | .004 | — |
| Median b | 30 (19, 48) | 30 (16, 47) | < .001 | 0.65 (0.55–0.77) |
| <25 y, n (%) | 206 (13.0) | 661 (18.8) | ||
| Gravidity, n a | 4.4 ± 1.8 | 2.7 ± 1.2 | < .001 | — |
| Prepregnancy body mass index, kg/m 2 a | 27.0 ± 7.2 | 26.6 ± 6.9 | .042 | −0.44 (−0.86 to −0.02) |
| Body mass index, n (%) | ||||
| Lean | 62 (3.9) | 155 (4.4) | .435 | — |
| Normal | 702 (44.5) | 1619 (46.0) | .306 | — |
| Overweight | 359 (22.8) | 832 (23.7) | .480 | — |
| Obese | 454 (28.8) | 909 (25.9) | .029 | 1.16 (1.02–1.32) |
| Previous miscarriage, n (%) | 783 (49.6) | 1499 (42.5) | < .001 | 1.33 (1.17–1.50) |
| Black race, n (%) | 401 (25.4) | 726 (20.6) | < .001 | 1.31 (1.14–1.51) |
| Unmarried, n (%) | 549 (34.8) | 1031 (29.3) | < .001 | 1.29 (1.14–1.46) |
| Smoker, n (%) | 161 (10.2) | 188 (5.3) | < .001 | 2.01 (1.62–2.51) |
| Cerclage, n (%) | 181 (11.5) | 434 (12.3) | .385 | — |
| Medicaid, n (%) | 106 (6.7) | 230 (6.5) | .806 | — |
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