Hyperemesis Gravidarum

(Severe Morning Sickness; Persistent Vomiting of Pregnancy; HG)


Hyperemesis gravidarum (HG) is an uncommon condition characterized by frequent, persistent, and severe vomiting and nausea during pregnancy. As a result, you may be unable to take in a sufficient amount of food and fluids. It can cause a weight loss of more than 5% of your pre-pregnancy body weight. This can also cause dehydration and vitamin and mineral deficiencies. Treatment may require hospitalization. HG is a more severe form of nausea and vomiting of pregnancy (NVP), also called morning sickness. Morning sickness affects anywhere between 70% to 80% of pregnant women. HG is estimated to occur in up to 2% of pregnancies.


There are many theories about the causes of HG, but none have been confirmed. HG is a complex disease that is likely caused by many factors. Some of these include:
  • Vitamin B deficiency
  • Human chorionic gonadotropin (hCG)—hyperemesis most severe during period of highest hCG levels
  • Hyperthyroidism —may be a result of hCG levels
  • High levels of estrogen
  • A multiple pregnancy
  • Brain nausea-control-center sensitivity to pregnancy changes
The Brain May Be Cause of Nausea
Brainstem and brain
Copyright © Nucleus Medical Media, Inc.

Risk Factors

Factors that may increase your chance of HG include:
  • History of HG in previous pregnancies
  • Molar pregnancy—an abnormal mass made up of placental tissue which may or may not contain some fetal tissue
  • Mother or sister with HG
  • A multiple pregnancy
  • Young maternal age
  • No previous completed pregnancies
  • First-time pregnancy
  • Obesity

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