Pregnancy and fertility-related adverse outcomes associated withChlamydia trachomatisinfection: a global systematic review and meta-analysis

Abstract

BackgroundGenital chlamydia infection in women is often asymptomatic, but may result in adverse outcomes before and during pregnancy. The purpose of this study was to examine the strength of the relationships between chlamydia infection and different reproductive health outcomes and to assess the certainty of the evidence.MethodsThis review was registered and followed the Cochrane guidelines. We searched three databases to quantitatively examine adverse outcomes associated with chlamydia infection. We included pregnancy and fertility-related outcomes. We performed meta-analyses on different study designs for various adverse outcomes using unadjusted and adjusted analyses.ResultsWe identified 4730 unique citations and included 107 studies reporting 12 pregnancy and fertility-related outcomes. Sixty-eight studies were conducted in high-income countries, 37 studies were conducted in low-income or middle-income countries, and 2 studies were conducted in both high-income and low-income countries. Chlamydia infection was positively associated with almost all of the 12 included pregnancy and fertility-related adverse outcomes in unadjusted analyses, including stillbirth (OR=5.05, 95% CI 2.95 to 8.65 for case–control studies and risk ratio=1.28, 95% CI 1.09 to 1.51 for cohort studies) and spontaneous abortion (OR=1.30, 95% CI 1.14 to 1.49 for case–control studies and risk ratio=1.47, 95% CI 1.16 to 1.85 for cohort studies). However, there were biases in the design and conduct of individual studies, affecting the certainty of the overall body of evidence. The risk of adverse outcomes associated with chlamydia is higher in low-income and middle-income countries compared with high-income countries.ConclusionChlamydia is associated with an increased risk of several pregnancy and fertility-related adverse outcomes in unadjusted analyses, especially in low-income and middle-income countries. Further research on how to prevent the sequelae of chlamydia in pregnant women is needed.Trial registration numberCRD42017056818.

Online Japanese-Language Information on Lifestyle Factors Associated With Reduced Fertility: Content Analysis

“…In addition to genetic background and reproductive history, environmental factors and current lifestyle habits have been proposed as causes of male and female infertility [ 9 ]. According to large systematic reviews and meta-analyses, the lifestyle factors associated with reduced fertility are (1) sexually transmitted diseases, (2) psychological stress, (3) cigarette smoking, (4) alcohol use, (5) nutrition and diet, (6) physical activity and exercise, (7) underweight, (8) overweight and obesity, and (9) environmental pollutants [ 10 - 27 ]. Given the situation of one-third of Japanese couples currently or previously worrying about infertility, for those who are trying to conceive or hope to have a child in the future, knowledge about the lifestyle factors associated with reduced fertility may help to prevent infertility.…”

Chlamydia trachomatisand reproductive health: what can we learn from systematic reviews of observational studies?

“…Tang and colleagues have done a systematic review and meta-analysis,6 which substantially strengthen the completeness of the evidence base about the association between CT and adverse reproductive outcomes. They reviewed reports of 107 observational epidemiological studies (case–control, cohort or cross-sectional) published up to May 2018.…”

“…For outcomes with both univariable and multivariable analyses, the unadjusted estimate was higher than the adjusted estimate in 16 of 19 pairs, suggesting that confounding is present. For example, for preterm labour, the unadjusted and adjusted risk ratios in cohort studies were 1.54 (95% CI 1.48 to 1.60) and 1.09 (95% CI 1.03 to 1.15) and ORs in case–control studies were 1.29 (95% CI 1.11 to 1.50) and 1.15 (95% CI 0.95 to 1.39), respectively 6…”

“…Because of the wide scope of the review, there was little opportunity to discuss the questions about causality or of potential mechanisms for individual outcomes. For example, the authors suggest that there is increased evidence of associations with stillbirth and spontaneous abortion 6. However, these associations were only present in unadjusted analyses, the biological mechanism is unclear, and the certainty of the body of evidence was assessed as low or very low.…”

“…In an earlier systematic review, Olson-Chen et al examined eight adverse outcomes of pregnancy, but not fertility, and included 56 studies published between 1970 and 2013,8 with some overlap in outcomes and included studies with Tang et al . In both reviews, the strength of association was smaller in studies judged to be of better methodological quality 6 8. In neither review, however, did the authors identify which specific biases were associated with attenuation in the effect size.…”