«We can only extrapolate to humans, but in the mouse, our data show that the whole process [of egg maturation] takes 18 to 20 days, and we can detect this asymmetry by the second or third day of the process. (discovermagazine.com)
In 1976, Edwards realised that this was happening because a hormone given to the women beforehand to stimulate egg maturation later interfered with the pregnancy itself. (newscientist.com)
She discovered that in some species, environmental factors control egg maturation and subsequent ovulation; in others, such as rabbits, sexual intercourse with a male or even just his presence causes the release of the egg. (sciencemag.org)