Background: The in vivo developing embryo is naturally exposed to constant vibrations of around 6 Hz, increasing to 20 Hz when the oviductal fluid is mechanically agitated by the cilia. This study examines the effects on viability of subjecting human pronuclear oocytes and embryos to mechanical agitation during their in vitro culture before transplantation.

Methods: Metaphase-II oocytes were ICSI/IVF with morphologically normal spermatozoa and then divided into two groups according to whether the cells underwent mechanical agitation (20 Hz over 5 seconds once per hour) of the culture medium (Group 2, n=23) or were cultured without mechanical agitation (Group 1, n=23). The fertilization rate of oocytes was recorded 18 hours later. Embryo development was monitored every day during the whole period of in vitro culture up to the embryo transfer on day 3, 4 or 5.

Results: Pregnancy rates after the transfer of 3 Day embryos in Group 1 and Group 2 were 50% and 80%, and of 5 Day embryos in Group 1 and Group 2 were 36% and 73%, respectively.

Conclusions: The in vitro culture of human embryos in a medium subjected to regular short bursts of mechanical agitation drastically increases their development rate.