The advice given for the treatment of diarrhoea in pregnancy is no different from that given to non-pregnant people. Drinking plenty of fluids and resting the bowel by avoiding solid food for 12-24 hours is all that is needed. The foetus is very good at getting what it needs from you, and there is no evidence that a fluid-only diet for 24 hours poses any threat to the foetus. It is best (as for non-pregnant people) to avoid taking medication to stop the diarrhoea as this can prolong the episode, and might have potentially harmful effects. After the first day, a light diet should be taken, and gradually increased towards a normal intake. Most episodes of diarrhoea are due to viruses, and will go away with no treatment after a couple of days. If after three or four days the symptoms are not improving or you feel unwell in any other way, it would be wise to arrange to see your GP. An examination will reassure you that nothing serious is going on, and arrangements can be made to send a stool sample to the laboratory to look for bacterial infection.