Time-lapse evaluation of human embryo development in single versus sequential culture media--a sibling oocyte study.

Objective: To compare the dynamics of early development between embryos cultured in single and sequential media.

Design: Randomized, comparative study.

Setting: Private IVF centre.

Patients: A total of 446 metaphase II oocytes from 51 couples who underwent oocyte retrieval procedure for intracytoplasmic sperm injection. Forty-nine resulted in embryo transfer.

Intervention: Oocytes were split between single and sequential media produced by the same manufacturer and cultured in a time-lapse incubator.

Main Outcome Measures: Morphokinetic parameters until the embryos reached the 5-cell stage (t5), utilization, clinical pregnancy and implantation rates.

Results: Embryos cultured in single media were advanced from the first mitosis cycle and reached 2- to 5-cell stages earlier. There was not any difference between the durations for cell cycle two (cc2 = t3-t2) and s2 (t4-t3). The utilization, clinical pregnancy and implantation rates did not differ between groups. The proportion of cryopreserved day 6 embryos to two pronuclei oocytes was significantly higher in sequential than in single media.

Conclusions: Morphokinetics of embryo development vary between single and sequential culture media at least until the 5-cell stage. The overall clinical and embryological parameters remain similar regardless of the culture system.