Menstrual cycle shortest and longest cycle lengths is considered very irregular. The average menstrual cycle lasts 28 days. The variability of menstrual cycle lengths is highest for women under 25 years of age and is lowest, that is, most regular, for ages 25 to 39. Subsequently, the variability increases slightly for women aged 40 to 44. The luteal phase of the menstrual cycle is about the same length in most individuals (mean 14.13 days, standard deviation 1.41 days) whereas the follicular phase tends to show much more variability (log-normally distributed with 95% of individuals having follicular phases between 10.3 and 16.3 days).
The Great Pheromone Myth mice and rats is a vestigial organ in humans. Menstrual synchrony has long been viewed as a physiological phenomenon in humans that could only be explained by the exchange of pheromones among women. He argues, however, that methodological critiques of menstrual cycle research and recent research indicate the menstrual synchrony does not occur among women. Finally, he reviews the literature on human pheromones and argues that there are serious methodological issues in all studies reporting human pheromones and that no human pheromone has ever been definitively identified. His conclusion is that human pheromones are a myth that is driven in