When did she ovulate?
Some time ago New Scientist had an article on ovulation. Apparently, once ultrasound scanning became detailed enough that they could image the ovaries and egg production, the scientists running the study were startled to discover that there was no relationship between an egg being released into the fallopian tubes and a woman’s period. They discovered that egg production in the ovaries is on its own cycle; sometimes coinciding with the mensuration cycle, and other times not. I found the whole study fascinating in a “ooh, human bodies are *neat*” kind of way. Short answer: there’s really no definite way to say (without an ultrasound examination) of when ovulation has occurred.
