A Cochrane review included 31 studies. Twenty-one trials compared combined oral contraceptives (COCs); others examined different COC regimens, progestin-only pills, injectables, a vaginal ring, and implants. None included a placebo. No study was stratified by body weight (normal-weight versus overweight women). Results for desogestrel were often favorable regarding carbohydrate metabolism but inconsistent overall. Glucose and insulin means were more favorable for norethisterone in studies of progestin-only contraceptives. For other progestins, little or no difference was noted across trials.
Comment: The quality of evidence is downgraded by study quality (inadequate allocation concealment).