Pregnancies and time to pregnancy in women with and without a previous Chlamydia trachomatis infection

A previous chlamydia infection did not result in fewer pregnant women, but among women with a pregnancy intention, time to pregnancy was longer compared with women without a previous infection. Supplemental digital content is available in the text.
Background A Chlamydia trachomatis infection (chlamydia) can result in tubal factor infertility in women. To assess if this association results in fewer pregnant women, we aimed to assess pregnancy incidences and time to pregnancy among women with a previous chlamydia infection compared with women without one and who were participating in the Netherlands Chlamydia Cohort Study (NECCST). Methods The NECCST is a cohort of women of reproductive age tested for chlamydia in a chlamydia screening trial between 2008 and 2011 and reinvited for NECCST in 2015 to 2016. Chlamydia status (positive/negative) was defined using chlamydia screening trial–nucleic acid amplification test results, chlamydia immunoglobulin G presence in serum, or self-reported chlamydia infections. Data on pregnancies were collected via questionnaires in 2015–2016 and 2017–2018. Overall pregnancies (i.e., planned and unplanned) and time to pregnancy (among women with a pregnancy intention) were compared between chlamydia-positive and chlamydia-negative women using Cox regressions. Results Of 5704 women enrolled, 1717 (30.1%; 95% confidence interval [CI], 28.9–31.3) women was chlamydia positive. Overall pregnancy proportions were similar in chlamydia-positive and chlamydia-negative women (49.0% [95% CI, 46.5–51.4] versus 50.5% [95% CI, 48.9–52.0]). Pregnancies per 1000 person-years were 53.2 (95% CI, 51.5–55.0) for chlamydia negatives and 83.0 (95% CI, 78.5–87.9) for chlamydia positives. Among women with a pregnancy intention, 12% of chlamydia-positive women had a time to pregnancy of >12 months compared with 8% of chlamydia negatives (P < 0.01). Conclusions Overall pregnancy rates were not lower in chlamydia-positive women compared with chlamydia-negative women, but among women with a pregnancy intention, time to pregnancy was longer and pregnancy rates were lower in chlamydia-positive women. Trial registration number: Dutch Trial Register NTR-5597.