I think it is a common thing while pregnant- I just had that flu from hell and while at emergency, the (male) doctor says to me "so eighteen weeks pregnant right? I suppose you are now wetting yourself every time you cough?"... He was sooooo right- I had only cried to my DH the day before when I wet my pants while coughing
I am guessing vomitting would have a similar effect...... Ahhh, the joys.....