What causes hg in pregnancy

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Last updated: April 4, 2026

Quick Answer: HG, or hyperemesis gravidarum, is a severe form of nausea and vomiting during pregnancy. While the exact cause is unknown, it's strongly linked to high levels of the hormone human chorionic gonadotropin (hCG), which rises rapidly in early pregnancy.

Key Facts

What is Hyperemesis Gravidarum (HG)?

Hyperemesis gravidarum (HG) is a rare but serious condition characterized by extreme, persistent nausea and vomiting during pregnancy. It is a more severe form than the common 'morning sickness' experienced by many pregnant individuals. While morning sickness usually subsides by the second trimester and doesn't typically cause significant weight loss or dehydration, HG can persist throughout the entire pregnancy and lead to significant health complications for both the pregnant person and the fetus.

What Causes HG in Pregnancy?

The precise cause of hyperemesis gravidarum is not fully understood, but it is believed to be multifactorial, with hormonal changes playing a significant role. The most widely accepted theory points to the rapid increase in certain pregnancy hormones.

Hormonal Factors: The Role of hCG

The primary suspect in the development of HG is the hormone human chorionic gonadotropin (hCG). This hormone is produced by the placenta shortly after conception and is essential for maintaining the pregnancy. hCG levels rise dramatically in the first trimester, peaking around 8-11 weeks of gestation. In individuals with HG, hCG levels are often significantly higher than in those with typical morning sickness. Researchers believe that these exceptionally high levels of hCG may directly stimulate the vomiting center in the brain, leading to severe nausea and vomiting.

Another hormone, estrogen, also increases significantly during pregnancy and may contribute to nausea. Some studies suggest that the sensitivity of the pregnant person's body to these hormonal surges plays a crucial role. Individuals who are more sensitive to the effects of hCG and estrogen are more likely to develop HG.

Other Potential Contributing Factors

While hormones are considered the main driver, other factors can increase the risk or severity of HG:

Symptoms and Complications of HG

The symptoms of HG go far beyond mild queasiness. They can include:

The complications of untreated HG can be serious, including malnutrition, liver damage, kidney problems, nerve damage, and in rare instances, may even pose a risk to the life of the pregnant person. Fetal complications can include low birth weight and preterm birth, often related to the mother's inability to gain adequate weight and nutrients.

Diagnosis and Treatment

Diagnosing HG involves ruling out other causes of vomiting and assessing for signs of dehydration and malnutrition. Treatment focuses on managing symptoms, preventing dehydration, and ensuring adequate nutrition. This often requires hospitalization and may involve:

It's crucial for anyone experiencing severe nausea and vomiting during pregnancy to seek medical attention immediately to prevent serious complications.

Sources

  1. Hyperemesis gravidarum - WikipediaCC-BY-SA-4.0
  2. Hyperemesis gravidarum: Causes, risks, and treatments - Mayo Clinicfair-use
  3. Severe vomiting and morning sickness in pregnancy - NHSfair-use

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