The Preterm Prediction Study: Association of second-trimester genitourinary chlamydia infection with subsequent spontaneous preterm birth

OBJECTIVE: This study was undertaken to determine the association between g enitourinary tract infection with Chlamydia trachomatis and spontaneous pre term birth. STUDY DESIGN: Genitourinary tract infection with C trachomatis was determin ed with a ligase chain reaction assay of voided urine samples collected at 24 weeks' gestation (22 weeks' to 24 weeks 6 days' gestation) and 28 weeks' gestation (27 weeks' to 28 weeks 6 days' gestation). Case patients (sponta neous preterm birth at <37 weeks' gestation; n = 190) and control subjects (delivery at greater than or equal to 37 weeks' gestation, matched for race , parity, and center; n = 190) were selected from 2929 women enrolled in th e Preterm Prediction Study of the National Institute of Child Health and Hu man Development Maternal-Fetal Medicine Units Network. RESULTS: Genitourinary C trachomatis infection (11% overall) was significan tly more common among the case patients than among the control subjects at 24 weeks' gestation (15.8% vs 6.3%; P=.003) but not at 28 weeks' gestation (12.6% vs 10.9%; P=.61). Women with chlamydia infection were more likely to have bacterial vaginosis (54.1% vs 32.9%; P=.002) and a short cervical len gth (less than or equal to 25 mm; 33.0% vs 17.9%; P=.02) but not a body mas s index <19.8 kg/m(2) (35.0% vs 23.9%; P=.17) or a positive fetal fibronect in test result (7.1% vs 9.5%; P =.62). After adjustment for risk factors fo r spontaneous preterm birth, women with C trachomatis infection at 24 weeks ' gestation were 2 times as likely as uninfected women to have a spontaneou s preterm birth at <37 weeks' gestation (odds ratio, 2.2; 95% confidence in terval, 1.03-4.78) and 3 times as likely to have a spontaneous preterm birt h at <35 weeks' gestation (odds ratio, 3.2; 95% confidence interval, 1.08-9 .57). CONCLUSION: Genitourinary C trachomatis infection at 24 weeks' gestation wa s associated with a 2-fold to 3-fold increased risk of subsequent spontaneo us preterm birth.