They have inteviewed woman who do not have IBS and it is fairly typical for woman to have GI symptoms during or around their period. Which symptoms is pretty variable.Hormones vary during the month and hormones have wide-ranging effects on most systems of the body so it isn't too far fetched to assume the GI tract may respond.Also it is fairly common for things like ovary disease to cause GI problems, whether that is hormonal, or anatomical (the GI tract and the reproductive tract are close together so it could be one thing being unhappy and "spreading the misery" to those close by).K.