In vitro development and pregnancy outcomes for human embryos cultured in either a single medium or in a sequential...

To compare a single medium, with medium renewal on day 3, with a sequential media system for development of human embryos to the blastocyst stage and subsequent pregnancy outcome.

Prospectively randomized study using donor oocytes.

Private infertility clinic.

Oocytes were collected from 47 donors (mean +/- SD age = 25.6 +/- 3.5 years) from March to October 2006 and used for 79 patients (40.6 +/- 5.4 years). The patients were prospectively randomized to have their embryos cultured in a single medium or in a sequential media system.

The donor oocytes were fertilized with fresh patient partner sperm and the resultant zygotes cultured in either a single medium or a sequential media system from day 1 until the blastocyst stage. After endometrial preparation the embryos were transferred to the patients on day 5 or day 6.

In vitro embryo developmental characteristics and pregnancy and implantation rates.

In vitro development rates on days 3, 4, and 5 and implantation rates were significantly greater for embryos cultured in the single medium than for those cultured in the sequential media system.

A single medium was as good as or better than a sequential media system for human embryo culture from the zygote to blastocyst stage. The idea that a sequential media system is required for optimal development of the human embryo to the blastocyst stage is highly questionable.