According to the Bihar school of yoga, surya namaskar (if the woman has already been doing it) may be practised up to 12 week of conception. Can u imagine that:) And our Indian women become suddenly supine when they become pregnant. I remember, while training for my ttc (junior level, teacher's training) a Canadian lady had taught us the entire sivananda sequence to be done during pregnancy, including mayurasana (which, I personally believe, must not be attempted for obvious pressure it applies at the abdomen)... but that is how it is. Last time I was at the ashram I had to lead the Advanced teachers' (including the men, some of whom displayed great hostility at that!) through a `pregnancy' class!!!