Transactions from the Annual Meeting of the American Gynecological and Obstetrical Society
The epidemiology of threatened preterm labor: A prospective cohort study

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Objective

The purpose of this study was to describe the occurrence, timing, and outcomes of hospital-based diagnoses of preterm labor.

Study design

Administrative records identified hospital admissions for preterm labor among 2534 women in an ongoing cohort study. Factors that were considered risks for prematurity were examined by logistic regression for an association with any preterm labor diagnosis, a preterm labor diagnosis <33 weeks of gestation, or ≥33 weeks of gestation.

Results

Of 234 women (9%) who experienced hospitalization for preterm labor, 90 women (38%) were delivered in the first episode. Previous preterm birth consistently was associated with a diagnosis of preterm labor. Reporting a sexually transmitted infection (odds ratio, 1.8; 95% CI, 1.1-3.0) or bacterial vaginosis (odds ratio, 2.6; 95% CI, 1.7-4.1) early in pregnancy was associated with hospitalization for preterm labor between 24 and 32 weeks of gestation.

Conclusion

The incidence of first-time hospitalization for preterm labor was 9%, with most episodes not resulting in preterm birth. Previous preterm birth was associated therefore with a preterm labor diagnosis.

Section snippets

Material and methods

The Pregnancy, Infection, and Nutrition (PIN) study was a prospective cohort study that was designed to identify determinants of preterm birth. The cohort included pregnant women who sought care from prenatal clinics at the Wake County Human Services Department, Wake Medical Center/Wake Area Health Education Center, and the University of North Carolina (UNC) Healthcare System.5 The study included singleton pregnancies in women who speak English, who were >16 years of age at enrollment, who had

Results

The group was balanced between white (57%) and black women (43%) who were between the ages 16 and 45 years (mean, 26 years). Eighty-one percent of the study subjects had completed at least high school (Table I); 1355 patients (53.5%) were parous, and 13.4% of the total population had a previous preterm birth. Almost 10% of the women reported a sexually transmitted infection (eg, herpes, Chlamydia, gonorrhea, or syphilis) in the current pregnancy, and almost 12% of them reported bacterial

Comment

Our data demonstrate an overall prevalence of first-time hospital admission for threatened premature labor of 9%, which is comparable to that observed by others.8, 9 Just over one half of our cohort was first diagnosed between 24 and 32 weeks of gestation, and earlier first-time admissions were less likely to culminate in preterm birth. Previous preterm birth was a predictor of admission for threatened premature labor for first admissions at both 24 to 32 weeks of gestation and 33 to 37 weeks

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Supported by the National Institute of Child Health and Human Development, grant Nos. PIN 1-HD28684, PIN 2-HD28684A, PIN 3-HD37584, and PIN 3/plus/-HD39373.

Presented at the 23rd Annual Meeting of the American Gynecological and Obstetrical Society, September 9-11, 2004, Bolton Landing, NY.

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