Hyperemesis Gravidarum: Extreme Morning Sickness

Morning sickness
Hyperemesis gravidarum, an extreme form of morning sickness, affects 1 in 50 pregnant women. (Image credit: Africa Studio/Shutterstock)

Hyperemesis gravidarum (HG) is an extreme form of morning sickness. Women who are affected by this condition experience severe nausea and persistent vomiting during some, most or all of their pregnancy. 

Some women show signs of hyperemesis gravidarum as early as the fourth week of pregnancy, and the condition can last up until delivery, said Marlena Fejzo, who researches the condition at the David Geffen School of Medicine at the University of California, Los Angeles (UCLA) and at the Keck School of Medicine of the University of Southern California. 

The problem can occur in about 1 in 50 pregnant women, Fejzo said. (In comparison, 7 in 10 pregnant women can have some form of nausea or vomiting or both, commonly known as "morning sickness," at some point in their first trimester, Fejzo noted.)

Women with HG may throw up as many as 10 or 20 times a day. They have trouble holding down any food or liquids, making it challenging to nourish themselves and their babies. 

Extreme morning sickness can leave women severely dehydrated, weak and exhausted. The condition may also lead to rapid weight loss during pregnancy, along with vitamin and mineral deficiencies that might ultimately land these women in the hospital.


Women with HG have prolonged periods of nausea and vomiting. Unable to keep up their intake of food or liquids, women may become dehydrated and develop electrolyte imbalances and nutritional deficiencies. Constantly vomiting can reduce levels of important vitamins and minerals, such as thiamine (vitamin B1), potassium, sodium and magnesium.  

"These symptoms occur at a time women are supposed to be eating healthy during pregnancy," Fejzo told Live Science. But instead, women can show signs of malnutrition and starvation, she said.  

The condition may be diagnosed when a woman loses 5 percent or more of her pre-pregnancy weight and has other health problems stemming from dehydration, according to the American College of Obstetricians and Gynecologists.  

Another common symptom is that women with HG have an extreme sensitivity to smell, Fejzo said. It's not just food and cooking smells; it can also be perfumes or just about anything, she explained. 

Certain smells may cause a wave of nausea and vomiting, and women may also be sensitive to light, noise and temperature changes. A woman with the condition may confine herself to a separate room in her home to minimize her exposure to these potential triggers. 

Some women's symptoms of HG may begin to improve by the 15th to 20th week of pregnancy, while other women will have frequent relapses throughout pregnancy or have symptoms until they deliver.

Some women with HG experience hypersalivation, or an overproduction of saliva, which can worsen nausea, Fejzo said. They have tons of saliva, but the cause of this overproduction of saliva in women with HG is not known, she said. 

HG is hard on a woman's body both physically and mentally, and it can interfere with her home, work and social life. She may feel so sick and wiped out that she might need to stop working and spend much of the day resting in bed. 

Pregnancy is supposed to be a happy time, but women with HG feel horrible, Fejzo said. They may be unable to eat and drink, and they often can't be around other people, which can make it an extremely stressful, depressing and isolating time for them, she explained. 

Studies have found that the condition can be so distressful that about 10 percent to 15 percent of women with HG choose to terminate their pregnancies, Fejzo said. 

Risk factors

If a woman has HG during her first pregnancy, she is extremely likely to have the condition in subsequent pregnancies. The recurrence rate is about 80 percent, Fejzo said.

The condition also tends to run in families. In a study done by Fejzo and her colleagues, the researchers found that women with sisters who had HG were about 17 times more likely to also experience severe morning sickness during their pregnancies compared to women without HG. 

When researchers dug even deeper into the family trees of women with HG, they found even more evidence of a hereditary component. A woman with HG was more likely to have a mother who had the condition, and the family history of extreme nausea and vomiting in pregnancy could also be traced to both grandmothers of a woman with HG. 

The findings showed that 18 percent of women with HG had a maternal grandmother who had the condition and 23 percent had a paternal grandmother affected by it. This suggests the risk for HG can be inherited from a woman's mother or father. 

Besides genetics, three other known risk factors for HG include being pregnant with multiples, such as twins or triplets; being pregnant with a girl; or having a history of motion sickness or migraines, according to the American College of Obstetricians and Gynecologists.

These three risk factors only slightly increase a woman's risk for HG, and it certainly doesn't mean that if a woman is carrying a boy, she won't get the condition, Fejzo noted. 


The cause of HG is not yet known, but more and more evidence is pointing to a strong genetic link, Fejzo told Live Science. 

One of the long-standing misconceptions about hyperemesis gravidarum is that it is psychosomatic (meaning all in a person's head) or has a psychological cause, such as a rejection of pregnancy or a fear of childbirth or motherhood, Fejzo said. But research has debunked these ideas, she noted. 


IV fluids: If a woman is severely dehydrated and cannot hold down any liquids, she will be given intravenous fluids to restore fluids and replace electrolytes, Fejzo said. Vitamin supplementation, especially with thiamine (B1), may also be necessary if a woman can't hold down her prenatal vitamin, Fejzo said. 

Nutritional therapy: Some women with severe HG who cannot hold down any food may need to be given enteral feedings (through the stomach or intestines) or parenteral feedings through another route, such as via a vein. Tube feeding may be necessary to ensure that the mother and fetus are getting enough nutrients to sustain the pregnancy. 

Anti-emetic medication: Although pregnant women are often afraid of taking any medications during pregnancy, anti-emetic medications — used to prevent vomiting — may be necessary in severe cases of HG. Women should discuss their safety as well as weigh their risks and benefits with their health care providers, Fejzo said. 

The three most commonly prescribed medications for HG in the United States are ondansetron (Zofran), metoclopramide (Reglan) and promethazine (Phenergan), Fejzo told Live Science. Studies suggest that Zofran is the most effective treatment, she said. 

This medication is typically used to relieve chemotherapy-related vomiting, Fejzo said. Zofran may help control the vomiting from HG, but it doesn't always help with the nausea, she said. 

Avoiding triggers: Women should stay away from any smells that seem to trigger nausea, Fejzo said. (Besides odors, noise and light may also worsen symptoms.) She also recommended that women keep windows open, if possible, and use a fan to blow cold air on their faces, which may ease nausea.

Getting some support. Other women who have experienced HG have banded together to form an extremely supportive community available to help those going through the condition and to make them feel less alone. Fejzo encouraged women to join an online HG support group via Facebook or turn to the HelpHer website, an online resource from the Hyperemesis Education and Research Foundation, for the latest information on HG. 

Fejzo and her colleagues at UCLA have also developed a new app for women with HG to track their symptoms, intakes and treatment. It's called the HG Care app, and it is currently being tested. 

Possible risks to mother

Women with severe symptoms of HG are the most vulnerable to the following conditions: 

Esophageal bleeding or esophageal damage can result from frequent vomiting, as can dental problems, such as loose teeth. 

Weight loss or little weight gain may occur after the first trimester. Working with a dietitian can be helpful for getting tips on improving fluid or food intake to slow weight loss and break the vomiting cycle. Medication to stop the vomiting may be necessary. Some studies have found that if pregnant women fail to gain weight for two trimesters, it could harm the baby

Signs of malnutrition, such as increases in ketones (substances produced in the liver when your blood sugar is high) or increased protein in the urine, may be indicative of starvation during pregnancy. Malnutrition could result in vitamin deficiencies and electrolyte imbalances, which could be dangerous for the mother, Fejzo said. 

Weakened muscles may develop from extensive bed rest. If women with HG don't stand up, walk or move around several times a day, their muscles can become weak and the women may develop blood clots in their legs, Fejzo said. 

Wernicke's encephalopathy, a serious and sometimes fatal brain disorder caused by a thiamine (vitamin B1) deficiency, can be avoided, Fejzo said. If a woman can't tolerate taking an oral prenatal vitamin and has not been able to eat for a week, she likely needs a shot of thiamine to prevent this deficiency, Fejzo said. 

Even after women with HG deliver their babies, they could be at increased risk for post-traumatic stress disorder (PTSD), a study done by Fejzo and her colleagues found. 

Possible risks to children

Children of women who had severe HG during pregnancy or women whose HG symptoms were not properly treated may be at increased risk of being born prematurely, being small for their gestational age or having low birth weights. A woman with HG may also lose her baby during pregnancy. 

Studies are just beginning to investigate the possible long-term effects on children. So far, researchers have found that children whose mothers had HG were about three times more likely to develop speech or other neurodevelopmental delays than children whose mothers did not have severe morning sickness, Fejzo said. 

A woman's stress and anxiety during pregnancy, as well as her malnutrition, may affect the brain of the developing fetus, researchers have said. 

Another study done by Fejzo found that children who had mothers with HG were 3.5 times more likely to have emotional and behavioral problems by the time they reached their 30s, compared to children of mothers without the condition. Those problems can include such as anxiety, depression and bipolar disorder.

Additional resources

Live Science Contributor

Cari Nierenberg has been writing about health and wellness topics for online news outlets and print publications for more than two decades. Her work has been published by Live Science, The Washington Post, WebMD, Scientific American, among others. She has a Bachelor of Science degree in nutrition from Cornell University and a Master of Science degree in Nutrition and Communication from Boston University.