Blastocyst transfer in day-5 embryo transfer depends primarily on the number of oocytes retrieved and not on age.

OBJECTIVE

To analyze the effects of patient age and treatment cycle number on the occurrence of blastocyst transfer and subsequent implantation.

DESIGN

Prospective study.

SETTING

Department of endocrinology and reproduction.

PATIENT(S): All 1,099 women had day-5 transfers after IVF or intracytoplasmic sperm injection treatment.

INTERVENTION(S): All patients were checked for embryo development in vitro in consecutive day-5 transfer cycles. Two blastocysts or three lesser-developed embryos were transferred.

MAIN OUTCOME MEASURE(S): Blastocyst formation rate or clinical pregnancy/implantation rate.

RESULT(S): Of 929 patients in the first cycle, 545 (59%) had at least one blastocyst available for ET. Among 151 patients with a blastocyst in cycle 1, 77 developed one or more blastocysts in cycle 2 (51%). Fifty of 143 patients without a blastocyst in cycle 1 had at least one blastocyst in cycle 2 (35%). After subdivision of all day-5 ETs according to the first four cycles, the following implantation rates per embryo were found for ET with one or more blastocysts: cycle 1 (n = 545), 23%; cycle 2 (n = 264), 23%; cycle 3 (n = 110), 14%; and cycle 4 (n = 27), 12%, and with noncavitating embryos, respectively: (n = 384) 6%, (n = 193) 6%, (n = 94) 2%, and (n = 35) 3%. The negative correlation of the age of the woman on blastulation depended primarily on the number of oocytes retrieved.

CONCLUSION(S): The blastocyst implantation rate decreased after cycle 2. Biologic ovarian age, rather than chronologic age, determines the frequency of blastocyst transfer or pregnancy rate.