I wouldn't say it's affected my career in the big picture in terms of choice or progression, but it has affected my performance at work.
Prior to having children mine were painful, as in sometimes curl up in tears on the disgusting stockroom floor because I'm too cramped up to stand, and lie there waiting to be found type of painful. The good news was that they were irregular and sporadic so I didn't have to go through it every month. The bad news was that by the time my body announced its arrival, it was too late for the prescription painkillers to really kick in for the first day. I always tried the soldier on approach, but sometimes I was too obviously struggling and sent home. Other times I could plough on with medication and a hot water bottle... not an ideal accessory in a room full of teenaged pupils (heat patches were a great discovery although there were times when.my shirt would ride up and horrified teenagers would ask why there was a sanitary towel stuck to my vest
) Neither heat option is the epitome of professionalism, but it was that or several times a year phone in sick and arrange cover.
I do wonder where the new uterus came from after having children. I can actually predict which week they will turn up in which is a marvellous novelty and so useful compared to guess the month! I can control any pains with regular painkillers. I do however notice that a day or two before and on the first day that my mental stamina goes and when I was working, it was not a productive time for things like catching up on marking. Mentally it is like wading through soup.
I think it would be better if we can accept that many women are significantly affected by our periods and where possible, a little flexibility to work around them wouldn't go amiss.
I must say that I'm glad my periods went this way around, partly because I'm feeling the benefit now
but really because I can appreciate that women's experiences vary, and the menstrual cycle can have a clear effect on life. If I'd had these periods first, there's a danger that I could have fallen into the "they're not so bad, plough on" attitude.