In the hours that follow fertilization, the cytoplasm inside mouse eggs moves with a characteristic, although not uniform, rhythm. Screening human embryos for these movements might boost the success rate of in vitro fertilization (IVF).

Magdalena Zernicka-Goetz at the University of Cambridge, UK, and her team took rapid time-lapse microscopy footage of mouse eggs for two hours after sperm entry and measured the cells' fluid dynamics. Fertilization induced oscillations in the cells' calcium ion concentration, which, in turn, caused the eggs' protein skeletons to contract rhythmically.

Embryos in which contractions had been more rapid but less frequent were more likely to lead to successful pregnancy in surrogate mice.

Nature Commun. 2, 417 (2011)