Development of hyperemesis gravidarum is the result from multiple genetic mutations. Hyperemesis gravidarum usually develops during the 2nd trimester of pregnancy.

The pathophysiology of nausea and vomiting during pregnancy is not entirely understood. It is believed to be associated with human chorionic gonadotropin (hCG), a hormone produced by the placenta during pregnancy [5].

The pathophysiology of nausea and vomiting during pregnancy is not entirely understood. It is believed to be associated with [human chorionic gonadotropin (hCG)], a hormone produced by the placenta during pregnancy. ^[1]

According to most studies, it is believed to be multifactorial and related to some genetic, endocrine and gastrointestinal factors.

• Genetic:
  • More commonly associated with female monozygotic twins
  • Higher risk in patients whose mothers had HG
  • Higher risk among patients that had history of HG in their first pregnancy ^[2]

• Endocrine:
  • hCG, estrogen and progesterone are linked to nausea and vomiting in pregnancy ^[2]
  • Patients that experience nausea and vomiting while taking combined oral contraceptive pills are more likely to develop HG in pregnancy. ^[3]

• Human Chorionic Gonadotropin hormone:
  • Peaks at weeks 9-12, which correlates with an increased severity of nausea and vomiting during pregnancy, as well as the symptoms of hyperemesis gravidarum.
  • The concentration of hCG in the blood and urine is found to be higher among patients with worsened symptoms of HG.^{[2] [4]}

• Gastrointestinal:
  • The presence of H pylori in the intestine is found to be commonly associated in women that experience HG. ^[5]