Hyperemesis gravidarum means severe vomiting in pregnancy. It is characterised by the inability to keep even fluids down, with consequent weight loss and dehydration. It affects round about 1 in 1000 pregnancies, and younger women with multiple pregnancies are more at risk. It can be precipitated by a urinary tract infection, which should be treated promptly. Women with protracted severe vomiting who become dehydrated are at risk of developing liver damage and therefore need prompt treatment to reverse the dehydration and stop the vomiting. Very rarely, in order to save the mother, it may be necessary to sacrifice the pregnancy.