Received August 01, 2008
Accepted August 28, 2008

Objective: The objective of this study was to assess blastocyst development and pregnancy rates after embryo culture in the WOW system, which consists of a microenvironment obtained through “micro-holes” on a culture dish cavity. Methodology: The present study was carried out in 14 patients aged between 20 and 43 years that were submitted to in-vitro fertilization treatment. The embryos were cultured in WOW dishes until day 5 of their development (d5). Transfer was carried out on day 3 (d3), on day 5, or on both days. Results: From 112 embryos obtained, 28 were transferred on d3, and 84 placed in culture medium until d5, of which 25 became blastocysts (25%). From 14 patients, 11 had classes I and II embryos transferred on d3, and their remaining embryos staying in culture until d5. The other 3 patients had embryos transferred only on d5. From the 11 patients that received the embryos on d3, 7 also had blastocysts transferred on d5 (64%). Therefore, from the 14 patients in the study, 10 received blastocysts, and a total of 8 patients got pregnant (57%). Discussion: The pregnancy rate obtained in this study demonstrates that the WOW system seems to be a promising alternative for the development of in-vitro embryos. The positive effect may be explained by the extremely low amount of medium around the embryo, allowing the embryo to keep its own environment with an efficient manifestation of autocrine and paracrine factors.