BACKGROUND: For many subfertile women, assisted reproductive techniques (ART) is the only hope for a pregnancy and live birth. The combined oral contraceptive pill (OCP) given prior to the hormone therapy in an IVF cycle may result in better pregnancy outcomes of ART. OBJECTIVES: To assess whether pre-treatment with combined OCPs, progestogens or estrogens in ovarian stimulation protocols affects outcomes in subfertile couples undergoing ART. SEARCH STRATEGY: We searched the Cochrane Menstrual Disorders and Subfertility Group Specialised Register, The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, PsycINFO. Other electronic resources on the Internet, reference list of relevant articles were also searched as well as the ESHRE abstracts (2008). All these searches were conducted in November 2008. SELECTION CRITERIA: Randomised controlled trials of pre-treatment with combined OCP, progestogen or estrogen in subfertile women undergoing IVF/ICSI. DATA COLLECTION AND ANALYSIS: Two authors independently extracted the data and assessed risk of bias. We calculated Peto odds ratios for dichotomous data and weighted mean difference for continuous variables. Authors of trials were contacted in case of missing data. MAIN RESULTS: No evidence of effect was found with regard to the number of live births when using a pre-treatment. However, the combined OCP in GnRH antagonist cycles, compared to no pre-treatment, is associated with fewer clinical pregnancies (Peto OR 0.69, P = 0.03) and more days and a higher amount of gonadotrophin therapy (respectively: MD 1.44, P <0.00001; and MD 691.69, P <0.00001).