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Adherence compounds in embryo transfer media for assisted reproductive technologies.

BACKGROUND
In order to increase the success rate of assisted reproductive technologies (ART), adherence compounds such as hyaluronic acid and fibrin sealant have been introduced into subfertility management. Adherence compounds are added to the embryo transfer medium in order to increase the likelihood of embryo implantation, with the potential for higher clinical pregnancy and live birth rates.


OBJECTIVES
To determine whether embryo transfer media containing adherence compounds affect the live birth rate in ART compared to transfer media without adherence compounds.


SEARCH STRATEGY
The Menstrual Disorders and Subfertility Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and PsycINFO electronic databases were searched (to 26th May 2009) for publications which described randomised controlled trials of the addition of adherence compounds to embryo transfer media. Furthermore, reference lists of all obtained studies were checked and conference abstracts handsearched.


SELECTION CRITERIA
Only truly randomised controlled trials comparing embryo transfer media containing adherence compounds with transfer media without (or with lower doses of) adherence compounds were included. The adherence compounds that were evaluated were hyaluronic acid and fibrin sealant.


DATA COLLECTION AND ANALYSIS
One review author selected the trials for inclusion according to the above criteria, after which two authors independently extracted the data for subsequent analysis. The statistical analysis was performed in accordance with the guidelines developed by The Cochrane Collaboration.


MAIN RESULTS
Sixteen studies with a total of 3698 participants were analysed. One studied fibrin sealant, the other 15 studied hyaluronic acid. There was no evidence of a treatment effect of fibrin sealant as an adherence compound. For hyaluronic acid, there was no evidence of a treatment effect on live birth rate. Evidence of treatment effects could be found for the clinical pregnancy rate (OR 1.41, 95% CI 1.22 to 1.63; P < 0.00001) and the multiple pregnancy rate (OR 1.86, 95% CI 1.49 to 2.31; P < 0.00001), with higher rates in the hyaluronic acid groups. No evidence of treatment effect was found for the other outcomes.


AUTHORS' CONCLUSIONS
There is evidence of an improved clinical pregnancy rate with the use of adherence compounds in ART cycles but no evidence of an effect on live birth rate. The increase in multiple pregnancy rate may be the result of the use of a combination of an adherence compound and a policy of transferring more than one embryo. Further studies of adherence compounds with single embryo transfer need to be undertaken.