Table I.

Clinical Results of Vitrified Human Blastocysts that Were Diluted Following Either a 6-Step or a 2-Step Dilution Method

	6-step	2-step
No. of cycles	66	85
No. of blastocysts thawed	209	261
No. (%) of blastocysts surviving	186 (89.0)	239 (91.6)
No. (%) of blastocysts hatched at ET	142 (76.3)	208 (87)
No. (mean) of blastocysts transferred	170 (2.6)	220 (2.6)
No. (%) of clinical pregnancies	27 (40.9)	39 (45.9)
No. (%) of blastocysts implanted	33 (19.4)	53 (24.1)

Note. After ET, surplus expanded blastocysts were vitrified on an EM-grid following artificial shrinkage. Vitrified blastocysts were warmed using either a 6-step or a 2-step dilution method with sucrose for cryoprotectant removal. Data reflect the postthaw survival, hatching, implantation, and clinical pregnancy rates in patients who participated in our thawing-ET program.