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

Am J Obstet Gynecol. 2000 Sep;183(3):662-8. doi: 10.1067/mob.2000.106556.


Objective: This study was undertaken to determine the association between genitourinary tract infection with Chlamydia trachomatis and spontaneous preterm birth.

Study design: Genitourinary tract infection with C trachomatis was determined 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 (spontaneous preterm birth at <37 weeks' gestation; n = 190) and control subjects (delivery at >/=37 weeks' gestation, matched for race, parity, and center; n = 190) were selected from 2929 women enrolled in the Preterm Prediction Study of the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

Results: Genitourinary C trachomatis infection (11% overall) was significantly 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 (57.1% vs 32.9%; P =.002) and a short cervical length (</=25 mm; 33.0% vs 17.9%; P =.02) but not a body mass index <19.8 kg/m(2) (35.0% vs 23.9%; P =.17) or a positive fetal fibronectin test result (7.1% vs 9.5%; P =.62). After adjustment for risk factors for spontaneous preterm birth, women with C trachomatis infection at 24 weeks' gestation were 2 times as likely as uninfected women to have a spontaneous preterm birth at <37 weeks' gestation (odds ratio, 2.2; 95% confidence interval, 1.03-4.78) and 3 times as likely to have a spontaneous preterm birth at <35 weeks' gestation (odds ratio, 3.2; 95% confidence interval, 1.08-9.57).

Conclusion: Genitourinary C trachomatis infection at 24 weeks' gestation was associated with a 2-fold to 3-fold increased risk of subsequent spontaneous preterm birth.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Case-Control Studies
  • Chlamydia Infections / complications*
  • Chlamydia Infections / epidemiology
  • Chlamydia trachomatis* / genetics
  • Chlamydia trachomatis* / isolation & purification
  • DNA Ligases
  • DNA, Bacterial / urine
  • Female
  • Female Urogenital Diseases / microbiology*
  • Gene Amplification
  • Gestational Age*
  • Humans
  • Obstetric Labor, Premature / microbiology*
  • Pregnancy
  • Pregnancy Complications, Infectious*
  • Pregnancy Trimester, Second
  • Retrospective Studies
  • Risk Factors


  • DNA, Bacterial
  • DNA Ligases