Cryopreservation: the practicalities of evaluation.

An attempt was made to integrate data from cryopreserved embryos with those from fresh embryos to obtain a realistic assessment of the role of cryopreservation in assisted reproductive treatment. Principles were applied to previously published data from a large prospective randomized multicentre study comprising recombinant and urinary follicle stimulating hormone in in-vitro fertilization.