Objectives A better understanding of Chlamydia trachomatis infection (chlamydia)–related sequelae can provide a framework for effective chlamydia control strategies. The objective of this study was to estimate risks and risk factors of pelvic inflammatory disease (PID), ectopic pregnancy and tubal factor infertility (TFI) with a follow-up time of up until 8 years in women previously tested for chlamydia in the Chlamydia Screening Implementation study (CSI) and participating in the Netherlands Chlamydia Cohort Study (NECCST).
Methods Women who participated in the CSI 2008–2011 (n=13 498) were invited in 2015–2016 for NECCST. Chlamydia positive was defined as a positive CSI-PCR test, positive chlamydia serology and/or self-reported infection (time dependent). Data on PID, ectopic pregnancy and TFI were collected by self-completed questionnaires. Incidence rates and HRs were compared between chlamydia-positive and chlamydia-negative women corrected for confounders.
Results Of 5704 women included, 29.5% (95% CI 28.3 to 30.7) were chlamydia positive. The incidence rate of PID was 1.8 per 1000 person-years (py) (1.6 to 2.2) overall, 4.4 per 1000 py (3.3 to 5.7) among chlamydia positives compared with 1.4 per 1000 py (1.1 to 1.7) for chlamydia negatives. For TFI, this was 0.4 per 1000 py (0.3 to 0.5) overall, 1.3 per 1000 py (0.8 to 2.1) and 0.2 per 1000 py (0.1 to 0.4) among chlamydia positives and negatives, respectively. And for ectopic pregnancy, this was 0.6 per 1000 py (0.5 to 0.8) overall, 0.8 per 1000 py (0.4 to 1.5) and 0.6 per 1000 py (0.4 to 0.8) for chlamydia negatives. Among chlamydia-positive women, the strongest risk factor for PID was symptomatic versus asymptomatic infection (adjusted HR 2.88, 1.4 to 4.5) and for TFI age <20 versus >24 years at first infection (HR 4.35, 1.1 to 16.8).
Conclusion We found a considerably higher risk for PID and TFI in chlamydia-positive women, but the incidence for ectopic pregnancy was comparable between chlamydia-positive and chlamydia-negative women. Overall, the incidence rates of sequelae remained low.
Trial registration NTR-5597.
- chlamydia trachomatis
- pelvic inflammatory disease
- ectopic pregnancy
- tubal factor infertility
- cohort study
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Handling editor Jane S Hocking
Contributors All authors developed the study design. BMH collected the data for NECCST and performed among others the laboratory analyses. SAM coordinated the laboratory analyses. BMH led on the statistical analyses with oversight of IVFvdB and BHBvB. The data interpretation was done by BMH, IVFvdB, BHBvB and SAM and discussed with JEAMvB, MABvdS, JAL, HMG, CJPAH and NHTMD-M. All authors contributed to drafting and revision of the paper and all authors approved the final manuscript.
Funding This work was supported by the Netherlands Organisation for Health Research and Development (ZonMW Netherlands, a governmental organisation grant (registration no. 50-53000-98-103)) and Research Funding from the Ministry of Health, Welfare and Sports to the Centre of Infectious Disease Control.
Disclaimer The funders had no role in study design, data collection and analysis, interpretation of data, decision to publish or preparation of the manuscript.
Competing interests None declared.
Patient consent for publication Obtained.
Ethics approval This study was approved by the Medical Ethical Committee Noord-Holland, Alkmaar, the Netherlands (NL 51553.094.14/M014-042).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement On request, (anonymised) data and available biological material can be provided for research related to STI, after approval by an advisory committee.
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