Vomiting and heartburn

Abstract

The present concept of the vomiting mechanism is that emesis may be induced by direct action on the vomiting centre in the medulla or by lowering its threshold to stimulation. Excitation of the vomiting centre may result from direct visceral impulses or be secondary to stimulation of the chemoreceptor trigger zone. In early pregnancy both oestrogen and human chorionic gonadotrophin have been suspected as aetiological factors. When morning sickness is severe it is not uncommon for it to recur in the last few weeks of pregnancy, after the presenting part engages in the pelvis.