Many women, and indeed many clinicians, believe that taking a combination oral contraceptive pill (i.e., one that contains 2 ingredients, estrogen and progestin) will result in weight gain. Such perceptions often lead to a significant number of women (especially younger ones) being reluctant to use this highly effective method of contraception, and also cause many women who are already using this method to stop using it and switch to other methods in the process. However, is there indeed a link between the use of compounded oral contraceptives and weight gain? In 2014, Gallo and other experts conducted a study on the topic of whether compounded oral contraceptives have an effect on body weight. They searched all studies on combination oral contraceptives in CENTRAL, MEDLINE, POPLINE, EMBASE, LILACS, Clinicaltrial.com, and ICTRP repositories through November 2013, and also contacted known investigators and pharmaceutical companies for unretrieved published and unpublished information and data from clinical trials. Randomized controlled trials of combination oral contraceptives written in English and applied for more than 3 cycles versus placebo or blank controls, or one combination oral contraceptive versus another combination oral contraceptive (differing in formulation, dose, method of administration, or duration of study) were included for further analysis. Data from these sources were analyzed and processed using RevMan software; and another investigator verified the information screened into the study and the processed data. For continuous data, mean differences (MDs) and 95% confidence intervals (CIs) were calculated for changes in weight at baseline and after administration of the contraceptive pill (or placebo, blank control) using fixed-effects models. For count information, such as the proportion of people who gained or lost weight to a particular value, the ratio (PetoOR, or OR) and 95% CI were calculated. A total of 49 clinical trials met the requirements for in-depth analysis studies. These clinical trials included 52 randomized controlled, comparisons of different contraceptives (or placebo); the results of four randomized controlled comparisons of contraceptives with placebo (or blank controls) did not support a causal relationship between the use of combination oral contraceptives or combination contraceptive skin patches (combination contraceptive patches) and weight change. Most comparisons between different combination oral contraceptives did not show substantial weight change. In addition, no difference was shown between groups in terms of discontinuation of oral contraceptives due to weight change, i.e., no increase in discontinuation of combination contraceptives or combination patches was observed among women due to weight change. Based on these findings, Gallo et al. concluded that although the available evidence is not sufficient to determine that the combination oral contraceptive pill has no effect on body weight at all, it is certain that the evidence for a modest effect of the combination oral contraceptive pill on body weight is still sufficient. Clinical trials evaluating the relationship between compounded oral contraceptives and changes in body weight require a control group of placebo or non-hormonal contraceptive methods to control for other factors that affect body weight, such as the effect of time on body weight.