about 10,000 women a year in the uk are affected by the debilitating hyperemesis gravidarum - a severe form of morning sickness which causes constant vomiting , crippling weakness and dehydration .
pregnant women with hyperemesis gravidarum - the severe morning sickness suffered by the duchess of cambridge during both her pregnancies triples the risk of developmental problems compared with women who have normal nausea and vomiting .