Regular (ICSI) versus ultra-high magnification (IMSI) sperm selection for assisted reproduction.

BACKGROUND: Subfertility is a condition found in up to 15% of couples of reproductive age. Gamete micromanipulation, such as intracytoplasmic sperm injection (ICSI), is very useful for treating couples with compromised sperm parameters. Recently a new method of sperm selection named 'motile sperm organelle morphology examination' (MSOME) has been described and the spermatozoa selected under high magnification (over 6000x) used for ICSI. This new technique, named intracytoplasmic morphologically selected sperm injection (IMSI), has a theoretical potential to improve reproductive outcomes among couples undergoing assisted reproduction techniques (ART).

OBJECTIVES: To compare the effectiveness and safety of IMSI and ICSI in couples undergoing ART.

SEARCH METHODS: We searched for randomised controlled trials (RCT) in electronic databases (Cochrane Menstrual Disorders and Subfertility Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO, CINAHL, LILACS), trials registers (ClinicalTrials.gov, Current Controlled Trials, World Health Organization International Clinical Trials Registry Platform), conference abstracts (ISI Web of knowledge), and grey literature (OpenGrey); in addition, we handsearched the reference lists of included studies and similar reviews. We performed the last electronic search on 8 May 2013.

SELECTION CRITERIA: We considered only truly randomised controlled trials comparing ICSI and IMSI to be eligible; we did not include quasi or pseudo-randomised trials. We included studies that permitted the inclusion of the same participant more than once (cross-over or 'per cycle' trials) only if data regarding the first treatment of each participant were available.

DATA COLLECTION AND ANALYSIS: Two review authors independently performed study selection, data extraction, and assessment of the risk of bias and we solved disagreements by consulting a third review author. We corresponded with study investigators in order to resolve any queries, as required.

MAIN RESULTS: The search retrieved 294 records; from those, nine parallel design studies were included, comprising 2014 couples (IMSI = 1002; ICSI = 1012). Live birth was evaluated by only one trial and there was no significant evidence of a difference between IMSI and ICSI (risk ratio (RR) 1.14, 95% confidence interval (CI) 0.79 to 1.64, 1 RCT, 168 women, I(2) = not applicable, low-quality evidence). IMSI was associated with a significant improvement in clinical pregnancy rate (RR 1.29, 95% CI 1.07 to 1.56, 9 RCTs, 2014 women, I(2) = 57%, very-low-quality evidence). We downgraded the quality of this evidence because of imprecision, inconsistency, and strong indication of publication bias. We found no significant difference in miscarriage rate between IMSI and ICSI (RR 0.82, 95% CI 0.59 to 1.14, 6 RCTs, 552 clinical pregnancies, I(2) = 17%, very-low-quality evidence). None of the included studies reported congenital abnormalities.

AUTHORS' CONCLUSIONS: Results from RCTs do not support the clinical use of IMSI. There is no evidence of effect on live birth or miscarriage and the evidence that IMSI improves clinical pregnancy is of very low quality. There is no indication that IMSI increases congenital abnormalities. Further trials are necessary to improve the evidence quality before recommending IMSI in clinical practice.