Background: Semen preparation techniques for assisted reproduction, including intrauterine insemination (IUI), were developed to separate the motile morphological normal spermatozoa. Leucocytes, bacteria and dead spermatozoa produce oxygen radicals that negatively influence the ability to fertilize the egg. The yield of as many motile, morphologically normal spermatozoa as possible might influence treatment choices and therefore outcomes.

Objectives: To compare the effectiveness of gradient, swim-up, or wash and centrifugation semen preparation techniques on clinical outcome in subfertile couples undergoing intrauterine insemination (IUI).

Search strategy: We searched the Menstrual Disorders and Subfertility Group Trials Register (13 January 2007), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to January 2007 ), EMBASE (1980 to January 2007), Science Direct Database (1966 to January 2007), National Research Register (2000 to 2007), Biological Abstracts (2000 to January 2007), CINAHL (1982 to October 2006) and reference lists of relevant articles. We also contacted experts and authors in the field.

Selection criteria: Parallel randomized controlled trials (RCTs) comparing the efficacy of semen preparation techniques used for subfertile couples undergoing IUI in terms of clinical outcome were included.

Data collection and analysis: Two reviewer authors independently assessed trial quality and extracted data. Study authors were contacted for additional information.

Main results: Five RCTs, including 262 couples in total, were included in the meta-analysis (Dodson 1998; Grigoriou 2005; Posada 2005; Soliman 2005; Xu 2000). Xu compared the three techniques; Soliman compared a gradient technique versus a wash technique; Dodson and Posada compared a gradient technique versus a swim-up technique; whereas Grigoriou compared swim-up versus a wash technique. No trials reported the primary outcome of live birth. There was no evidence of a difference between pregnancy rates (PR) for swim-up versus a gradient or wash and centrifugation technique (Peto OR 1.57, 95% CI 0.74 to 3.32; Peto OR 0.41, 95% CI 0.15 to 1.10, respectively); nor in the two studies comparing a gradient technique versus wash and centrifugation (Peto OR 1.76, 95% CI 0.57 to 5.44). There was no evidence of a difference in the miscarriage rate (MR) in two studies comparing swim-up versus a gradient technique (Peto OR 0.13, 95% CI 0.01 to 1.33).

Authors' conclusions: There is insufficient evidence to recommend any specific preparation technique. Large high quality randomised controlled trials, comparing the effectiveness of a gradient and/ or a swim-up and/ or wash and centrifugation technique on clinical outcome are lacking. Further randomised trials are warranted.