Why do women get hg in pregnancy

Content on WhatAnswers is provided "as is" for informational purposes. While we strive for accuracy, we make no guarantees. Content is AI-assisted and should not be used as professional advice.

Last updated: April 8, 2026

Quick Answer: Hyperemesis gravidarum (HG) is a severe form of nausea and vomiting during pregnancy that affects approximately 0.3-3% of pregnant women, with symptoms typically beginning between 4-6 weeks of gestation and often peaking around 9-13 weeks. The exact cause is multifactorial but strongly linked to elevated levels of human chorionic gonadotropin (hCG), with studies showing women with HG have hCG levels 50-100% higher than those with normal pregnancy nausea. Treatment often involves intravenous fluids, antiemetic medications, and nutritional support, with hospitalization required in about 1-2% of cases. Research published in 2018 in Nature Communications identified GDF15 as another key hormone involved, with higher levels correlating with more severe symptoms.

Key Facts

Affects 0.3-3% of pregnant women worldwide
Symptoms typically begin 4-6 weeks after conception
Associated with hCG levels 50-100% higher than normal pregnancy nausea
Hospitalization required in approximately 1-2% of affected women
2018 Nature Communications study identified GDF15 as contributing hormone

Overview

Hyperemesis gravidarum (HG) represents the most severe form of nausea and vomiting during pregnancy, distinguished from typical morning sickness by its intensity and potential complications. First described medically in the 19th century, HG gained broader recognition when Catherine, Duchess of Cambridge, was hospitalized for the condition during her pregnancies in 2012, 2014, and 2018. The condition affects approximately 0.3-3% of pregnant women globally, with variations across populations. Historically, HG was often misunderstood or dismissed as psychological, but modern research has established its biological basis. The economic impact is substantial, with studies estimating direct medical costs exceeding $200 million annually in the United States alone, plus additional indirect costs from lost productivity. Research accelerated significantly after 2011 when the HER Foundation established the first international HG registry to collect systematic data.

How It Works

The pathophysiology of hyperemesis gravidarum involves complex hormonal interactions, primarily centered on human chorionic gonadotropin (hCG). Produced by the placenta, hCG levels rise rapidly in early pregnancy, peaking around 8-11 weeks—coinciding with the worst HG symptoms for most women. Elevated hCG stimulates the chemoreceptor trigger zone in the brainstem, increasing sensitivity to nausea triggers. Additionally, hCG shares structural similarities with thyroid-stimulating hormone (TSH), which may explain why some women with HG develop transient hyperthyroidism. Research published in 2018 identified growth differentiation factor 15 (GDF15) as another key player; women with genetic variants producing higher GDF15 levels before pregnancy experience more severe symptoms when exposed to pregnancy-induced GDF15 increases. These hormonal effects combine with slowed gastric emptying and enhanced olfactory sensitivity to create a perfect storm of persistent nausea and vomiting that can lead to dehydration, electrolyte imbalances, and weight loss exceeding 5% of pre-pregnancy body weight.

Why It Matters

Hyperemesis gravidarum has significant medical and psychosocial consequences that extend beyond physical symptoms. Medically, untreated HG can lead to serious complications including Wernicke's encephalopathy from thiamine deficiency, esophageal tears from forceful vomiting, and preterm birth. Psychologically, women with HG experience higher rates of depression and anxiety during and after pregnancy, with one study showing 29% meeting criteria for post-traumatic stress disorder related to their HG experience. The condition also impacts family dynamics and career trajectories, with many women requiring extended leave from work. Recognition of HG as a legitimate medical condition has improved through advocacy efforts, leading to better treatment protocols and insurance coverage in many regions. Research continues to explore genetic factors, with the hope of developing targeted therapies that could prevent or mitigate this debilitating condition.