Why do women get hg

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Last updated: April 8, 2026

Quick Answer: Women get hyperemesis gravidarum (HG), a severe form of nausea and vomiting during pregnancy, due to hormonal changes, particularly elevated human chorionic gonadotropin (hCG) levels. It affects approximately 0.3-3% of pregnancies, with symptoms often starting around weeks 4-6 of gestation and potentially lasting throughout pregnancy. Risk factors include a history of HG, multiple pregnancies, and certain genetic predispositions. Treatment typically involves antiemetic medications, intravenous fluids, and nutritional support to prevent complications like dehydration and weight loss.

Key Facts

Hyperemesis gravidarum affects 0.3-3% of pregnancies worldwide
Symptoms typically begin between weeks 4-6 of pregnancy
Human chorionic gonadotropin (hCG) levels peak around weeks 8-12, correlating with severe symptoms
Without treatment, HG can lead to 5% or greater weight loss from pre-pregnancy weight
Intravenous rehydration is required in approximately 25% of hospitalized cases

Overview

Hyperemesis gravidarum (HG) is a severe form of nausea and vomiting during pregnancy that extends beyond typical morning sickness. First described medically in the 19th century, HG gained broader recognition when Catherine, Duchess of Cambridge, was hospitalized for it in 2012 and 2014 during her pregnancies. The condition affects approximately 0.3-3% of pregnancies globally, with variations across populations. Historically, HG was sometimes fatal before modern medical interventions; mortality rates have decreased significantly with improved treatment protocols. The economic impact is substantial, with estimated healthcare costs exceeding $1 billion annually in the United States alone due to hospitalizations and lost productivity. Research has accelerated in recent decades, with the HER Foundation establishing in 2000 to support patients and advance scientific understanding.

How It Works

Hyperemesis gravidarum develops through complex physiological mechanisms primarily driven by hormonal changes in early pregnancy. Elevated levels of human chorionic gonadotropin (hCG), produced by the placenta, directly stimulate the vomiting center in the brain's medulla oblongata. hCG levels typically peak between weeks 8-12 of gestation, coinciding with the most severe HG symptoms. Additionally, increased estrogen and progesterone levels may contribute by relaxing gastrointestinal smooth muscle and delaying gastric emptying. Genetic factors play a role, with women whose mothers had HG being approximately three times more likely to develop it. The condition may also involve thyroid dysfunction, as hCG can weakly stimulate thyroid receptors, potentially causing transient hyperthyroidism. Recent research suggests that Helicobacter pylori infection might exacerbate symptoms in some cases.

Why It Matters

Hyperemesis gravidarum has significant real-world consequences for maternal and fetal health. Untreated HG can lead to severe dehydration, electrolyte imbalances, and nutritional deficiencies, potentially causing Wernicke's encephalopathy or other neurological complications. Pregnancies complicated by HG have higher rates of preterm birth and low birth weight infants. The psychological impact is substantial, with many patients experiencing depression, anxiety, and even considering pregnancy termination. Economically, HG results in considerable healthcare expenditures and lost work productivity. Beyond physical effects, HG affects family dynamics and quality of life, sometimes requiring extended bed rest or hospitalization. Increased awareness has led to better treatment protocols and support systems, improving outcomes for affected women worldwide.