Hyperemesis gravidarum - Causes
The actual cause of hyperemesis gravidarum is not known with certainty. It is believed to be associated with the hormonal changes of pregnancy which are highest between the 9th and the 12th week of pregnancy. It is also thought that infection with the ulcer causing bacterium helicobacter pylori predisposes one to severe nausea and vomiting. Other conditions like stress and the sex of the baby are still speculative.