A study published online by the Journal of Advanced Nursing found that 87% of women seeking infertility treatment could not correctly identify which days of their menstrual cycle they were fertile, even though 68% said they had accurately timed intercourse in order to conceive.

Hampton, K. D., Mazza, D. and Newton, J. M. (2012), Fertility-awareness knowledge, attitudes, and practices of women seeking fertility assistance. Journal of Advanced Nursing. doi: 10.1111/j.1365-2648.2012.06095.x