Tang W, Mao J, Li KT, et al. - Researchers sought to estimate the strength of the relationships between chlamydia infection and different reproductive health outcomes. Further, they examined the certainty of the evidence. Among 4,730 identified unique citations, 107 studies reporting 12 pregnancy and fertility-related outcomes were included in this work. Of these, 68 studies reported outcomes from high-income countries, 37 studies reported outcomes from low-income or middle-income countries, and 2 studies reported outcomes from both high-income and low-income countries. Findings revealed a positive correlation of chlamydia infection with almost all of the 12 included pregnancy and fertility-related adverse outcomes in unadjusted analyses, including stillbirth and spontaneous abortion. However, the design and conduct of individual studies seemed to be affected by biases, influencing the certainty of the overall body of evidence. Relative to high-income countries, low-income and middle-income countries had a higher risk of adverse outcomes associated with chlamydia.