Causes
While there are numerous theories regarding the etiology of HG, none is as yet conclusive. It is thought that the cause is most likely not due to one factor alone and may vary between women depending on such factors as genetics, body chemistry and overall health. The disease is more frequently found with women pregnant with girls and twins.
The most studied theories suggest that it is an adverse reaction to the hormonal changes of pregnancy. In particular, hyperemesis gravidarum may be due to elevated levels of beta HCG (Human chorionic gonadotropin), as it is more common in multiple pregnancies and in gestational trophoblastic disease. This theory would also explain why hyperemesis gravidarum is most frequently encountered in the first trimester (often around 8 – 12 weeks of gestation), as HCG levels are highest at that time and decline afterward. It is thought that estrogen produces nausea and regurgitation of stomach acids in some women. There is also evidence that leptin may play a role in HG.
A recent study gives preliminary evidence that there may be a genetic component.
Read more about this topic: Hyperemesis Gravidarum