Time-lapse cinematographic analysis of hatching of normal and frozen—thawed cow blastocysts

: This paper describes time-lapse cinematography on cattle blastocysts hatching from the zona in vitro. Four normal morulae were taken on Day 6 and cultured for 5 days. During this period 3 formed normal blastocysts of which 2 hatched from the zona without undergoing any contractions. Early blastocysts were taken on Day 7, frozen and stored at low temperature. After thawing they were cultured; only 1 of the 11 behaved like the normal embryos, and the others underwent contractions and failed to hatch. These contractions could be interpreted as a sign of an alteration of the trophoblastic structure and properties.