PMS is an irritating and uncontrollable factor in many women's lives. A household of two women (or even close female friends who don't live together), often will experience this hormonal impairment either at or near the same time. There is no humor involved. There is no rational behavior involved. There is no way to stop and think and be the reasonable people we usually are. Our household is one of those.
Some months (not every month, just the once-in-a-while-oh-god-stand-back-because-I'm-looking-for-a-fight-and-you're-gonna-give-it-to-me-whether-you-want-to-or-not-goddamnit months), those hormones coursing through my system make me insanely reactive. To the slightest provocation. Or maybe even no provocation at all. Like the sun getting in my eyes and me not having my shades in my purse. Or the supermarket being out of asparagus when I have a whole meal planned around asparagus. Or gas costing over $2 a gallon and my tank being empty. Everyday things that normally I just move right past, accept with grace and seek alternative solutions... well, not an alternative solution for the gas. That one I just grit my teeth and cough up the dough. Gas is, unfortunately, more important in my life than asparagus OR my shades.
There are many jokes about men and pregnancy and how they couldn't handle it. I think that the majority of men could handle pregnancy, with labor and the whole child raising thing included even. I know many men who are strong enough to handle it (well... maybe). But PMS? Every 28 days? Over and over month in and month out for over 40 years of their lives? Childbirth they may survive, but if PMS hit them every month it would drop them in their tracks.