Colorado Center for Reproductive Medicine, Englewood, CO 80110, USA
Dear Sir,
We read the comments of Damario and Dumesic on our publication on blastocyst culture and transfer (Gardner et al., 1998) with interest. We were pleased to see that they agreed with our final conclusion of our paper that a further prospective trial on a non-selected group of patients is required to determine the final niche of blastocyst culture and transfer in human assisted reproductive technologies (ART).
According to their concerns with regard to the time of patient selection, the majority of patients received human chorionic gonadotrophin (HCG) on day 8. However, in those patients not given HCG on day 8, 10 follicles could clearly be seen at the time of ultrasound. It was assumed that there would be little, if any, atresia of such follicles over the following 1 or 2 days before HCG was administered. In addition, only patients who fitted the set criteria were approached to take part in the trial.
The reason for choosing patients with at least 10 follicles was not arbitrary, rather an analysis of previous patients attending our centre revealed that such a patient population represented 90% of high order multiple gestations (triplets or higher). It was therefore decided that this was the patient population that would have most to gain from blastocyst culture and transfer. Indeed our prospective trial verified this hypothesis. One point that should be born in mind during analysis of the study, was that it was both prospective and randomized. So in each arm of the trial, both day 3 and day 5 transfer consisted of a similar population of patients with the same number of oocytes and embryos. It was not that the day 5 transfers occurred in patients with a better prognosis. As such the data stands, and has confirmed that blastocyst culture and transfer has a niche in human ART, that being the elimination of high order multiple gestations, while maintaining high pregnancy rates.
Notes
1 To whom correspondence should be addressed
References
Gardner, D.K., Schoolcraft, W.B., Wagley, L. et al. (1998) A prospective randomized trial of blastocyst culture and transfer in in-vitro fertilization.Hum. Reprod., 13, 34343440.[Abstract]