Quality assessment – Case-Control (Health only).

1Valid case definition provided?; 2Cases/controls representative of the general population e.g. community recruitment?; 3Power calculation; 4Systematic selection process used to select cases/controls e.g. matching, random selection, population based; 5Refusal to participate reported and reasonable; 6Exposure accurately measured; 7Exposure measured identically in cases and controls; 8Blinding used; 9Direction of the relationship explained; 10Appropriate confounders measured and accounted for; 11Measure of effect provided (e.g. OR/RR);12Confidence Intervals provided; 13P-Value provided. aRecruitment at infertility clinics; bUnclear how many controls refused participation; cAmongst many other potential confounders, sexual behaviour, a common cause of RTIs, not accounted for; dLow (3%) refusal rate; eSelf-reported menstrual hygiene; fAlthough data collected on STIs, not clear if OR adjusted.