Chlamydia trachomatis immunoglobulin G3 seropositivity is a predictor of reproductive outcomes in infertile women with patent fallopian tubes

Fertil Steril. 2015 Dec;104(6):1522-6. doi: 10.1016/j.fertnstert.2015.08.022. Epub 2015 Sep 25.


Objective: To determine if Chlamydia trachomatis (C. trachomatis) seropositivity, as detected by the C. trachomatis elementary body (EB)-based enzyme-linked immunosorbent assay [EB ELISA] predicts pregnancy and pregnancy outcome among infertile women with documented tubal patency.

Design: Cohort study.

Setting: Outpatient clinics.

Patient(s): In all, 1,250 infertile women with documented tubal patency enrolled in 1 of 2 randomized controlled trials: Pregnancy in Polycystic Ovary Syndrome II; and the Assessment of Multiple Intrauterine Gestations From Ovarian Stimulation.

Intervention(s): Sera were analyzed for anti-C. trachomatis immunoglobulin G (IgG)1 and IgG3 antibodies, using a research C. trachomatis EB ELISA. The optical density (OD)405 readings of ≥ 0.35 and ≥ 0.1 were considered positive for IgG1 and IgG3, respectively.

Main outcome measure(s): Primary outcomes included pregnancy, live birth, and ectopic pregnancy. Log-linear regression was used to determine the relative risk after adjusting for age, race, treatment medication, smoking status, and current alcohol use.

Result(s): A total of 243 (19%) women were seropositive for anti-C. trachomatis IgG3. They tended to be nonwhite and smokers. Anti-C. trachomatis IgG3 seropositive women were significantly less likely to conceive (risk ratio [RR] 0.65, 95% confidence interval [CI] 0.52-0.83) or to have a live birth (RR 0.59, 95% CI 0.43-0.80); these associations were weakened after adjusting for number of hysterosalpingography-documented patent tubes (RR 0.73, 95% CI 0.56-0.97) and (RR 0.73, 95% CI 0.50-1.04), respectively. Anti-C. trachomatis IgG3 seropositive women who conceived had a ×2.7 risk (95% CI 1.40-5.34) of ectopic pregnancy.

Conclusion(s): Even in the presence of tubal patency, anti-C. trachomatis IgG3 seropositivity is associated with a lower likelihood of pregnancy. Anti-C. trachomatis IgG3 seropositive women have as high as 3 times the risk of ectopic pregnancy.

Clinical trial registration number: PPCOSII: NCT00719186 and AMIGOS: NCT01044862.

Keywords: Chlamydia trachomatis; ectopic pregnancy; infertility; pregnancy.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adult
  • Antibodies, Bacterial / blood*
  • Biomarkers / blood
  • Chi-Square Distribution
  • Chlamydia Infections / blood
  • Chlamydia Infections / complications
  • Chlamydia Infections / diagnosis
  • Chlamydia Infections / microbiology*
  • Chlamydia trachomatis / immunology*
  • Enzyme-Linked Immunosorbent Assay
  • Fallopian Tubes / diagnostic imaging
  • Fallopian Tubes / physiopathology*
  • Female
  • Humans
  • Immunoglobulin G / blood*
  • Infertility, Female / blood
  • Infertility, Female / diagnosis
  • Infertility, Female / microbiology
  • Infertility, Female / physiopathology
  • Infertility, Female / therapy*
  • Linear Models
  • Live Birth
  • Multivariate Analysis
  • Odds Ratio
  • Predictive Value of Tests
  • Pregnancy
  • Pregnancy Rate
  • Pregnancy, Ectopic / microbiology
  • Reproductive Techniques, Assisted*
  • Risk Assessment
  • Risk Factors
  • Serologic Tests
  • Treatment Outcome
  • Ultrasonography
  • Young Adult


  • Antibodies, Bacterial
  • Biomarkers
  • Immunoglobulin G

Associated data