Menstrual synchrony by chance when there is menstrual cycle variability. Yang and Schank argued that when there is cycle variability (i.e., either women have irregular cycles, have cycles of different frequencies, or both), most women will have the opportunity to experience synchrony even though it is a result of cycle variability and not a result of a mechanism such as the exchange of pheromones. For example, consider two women A and B. Suppose A has menstrual cycles that are 28 days long and B has cycles that are 30 days long. Suppose further that when A and B become close friends, B
Menstrual cup capable of growing on menstrual cups. However, there have only been two confirmed cases of toxic shock syndrome (TSS) associated with the use of the menstrual cups. The first case was a woman who had a history of Hashimoto’s thyroiditis and chronic menorrhagia. In the second case, the menstrual cup had been left in for 7 days. Menstrual cups are generally bell-shaped, with a few exceptions. Most brands use medical grade silicone as the material for the menstrual cup, although latex and thermoplastic elastomer are also options. Menstrual cups made from silicone are generally designed to last for 1–5 years.