Extended culture up to the blastocyst stage: a strategy to avoid multiple pregnancies in assisted reproductive technologies.

The aim of this study was to review the experience and outcomes of assisted reproduction cycles with embryos grown up to day 5 of development, comparing different parameters according to the ages of the patients. We retrospectively studied 1,874 assisted reproduction cycles where embryo culture was extended up to the fifth or sixth day of development. All IVF and ICSI cycles were included, comparing, according to patient age, the following rates: blastocyst formation, pregnancy, implantation and abortion.

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

Objective: 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.

Design: Prospectively randomized study using donor oocytes.

Setting: Private infertility clinic.

Centrifugation of 2-cell mouse ova: cytoplasm stratification and recovery.

Two-cell mouse ova, which were centrifuged for l h at 70 000-90 000xg, showed a precise stratification of the cytoplasm and an elongation of the nucleus. The ova were fixed at different times and observed by light and electron microscopy using cytochemical methods and detergent extractions. Within 40 min after centrifugation the normal-looking morphology was recovered except for the persisting lipid caps at the centripetal poles of the blastomeres.