Background: Weight gain is often considered a side effect of combination hormonal contraceptives, and many women and clinicians believe that an association exists. Concern about weight gain can limit the use of this highly effective method of contraception by deterring the initiation of its use and causing early discontinuation among users. However, a causal relationship between combination contraceptives and weight gain has not been established.

Objectives: The aim of the review was to evaluate the potential association between combination contraceptive use and changes in weight.

Search strategy: We searched the computerized databases MEDLINE, POPLINE, CENTRAL, EMBASE, and LILACS for studies of combination contraceptives. We also wrote to known investigators and manufacturers to request information about other published or unpublished trials not discovered in our search.

Selection criteria: All English-language, randomized controlled trials were eligible if they had at least three treatment cycles and compared a combination contraceptive to a placebo or to a combination contraceptive that differed in drug, dosage, regimen, and/or study length.

Data collection and analysis: All titles and abstracts located in the literature searches were assessed. Data were entered and analyzed with RevMan, and a second author verified the data entered. Depending on the data available, the weighted mean difference using a fixed effects model with 95% confidence intervals (CI) was calculated for the mean change in weight between baseline and post-treatment measurements or the Peto odds ratio with 95% confidence intervals was calculated using the proportion of women who gained or lost more than a specified amount of weight.

Main results: The three placebo-controlled, randomized trials did not find evidence supporting a causal association between combination oral contraceptives or a combination skin patch and weight gain. Most comparisons of different combination contraceptives showed no substantial difference in weight. In addition, discontinuation of combination contraceptives because of weight gain did not differ between groups where this was studied.

Authors' conclusions: Available evidence was insufficient to determine the effect of combination contraceptives on weight, but no large effect was evident.