What Is Hyperemesis Gravidarum During Pregnancy?

From symptoms to treatment options, here’s what to know about intense nausea and vomiting called hyperemesis gravidarum (HG) in pregnancy.

Young African American woman feeling nausea during breakfast time at dining room.
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If you have severe morning sickness, also called hyperemesis gravidarum (HG), you may wonder: Will I ever gain weight? Have I eaten anything this week? Can a fetus survive on iced tea alone?

According to the National Organization for Rare Disorders (NORD), while morning sickness is very common—affecting 50% to 90% of pregnant people—HG is rare affecting just 0.5% to 2% of pregnancies.

What Is Hyperemesis Gravidarum?

Hyperemesis gravidarum (HG) is severe and frequent nausea and vomiting during pregnancy. It can lead to dehydration and significant weight loss. In other words, it's morning sickness gone wild.

So whether you're struggling with HG, debating a diagnosis, or even just wondering what "HG" means, keep reading to learn more about hyperemesis gravidarum in pregnancy, including causes, symptoms, and treatment options.

What Causes HG in Pregnancy?

According to NORD, previous hypotheses about causes of HG that linked the condition to human chorionic gonadotropin (hCG), vitamin deficiency, metabolic conditions, reflux, bacterial infections, and psychological factors have since been disproven.

More current research, including a 2018 genome-wide association study, has implicated the GDF15 and IGFBP7 genes, which are responsible for placenta development and appetite.

Although certain lifestyle factors (getting rest, staying hydrated, and all those ginger tips) may be able to ease symptoms, rest assured your lifestyle isn't at fault for your HG symptoms. In fact, most of the known risk factors for HG are out of a person's control.

Risk Factors for Hyperemesis Gravidarum

According to the American College of Obstetricians and Gynecologists (ACOG), risk factors for HG include:

  • A multiple pregnancy (being pregnant with two or more fetuses)
  • A current or previous molar pregnancy
  • Higher maternal age
  • Having had morning sickness in a previous pregnancy
  • Having a first-degree relative who had HG
  • A history of motion sickness or migraines
  • Being pregnant with a female fetus

While having a history of HG in pregnancy does increase your risk of having it again in future pregnancies, you are not necessarily doomed to face HG with every pregnancy just because you have before. About half of people diagnosed with HG find that the symptoms recur in a subsequent pregnancy—but that also means that half of them don't!

Symptoms of Hyperemesis Gravidarum

So how do you know it's hyperemesis rather than run-of-the-mill morning sickness? Often via "a clinical diagnosis of exclusion," explains Jessie Rubin, M.D., an OB-GYN in Houston.

According to the National Library of Medicine, common HG symptoms include:

  • Severe nausea and vomiting during pregnancy
  • Excess salivation
  • Pregnancy weight loss
  • Dehydration symptoms, like dark urine, dry skin, weakness, dizziness, or fainting
  • Constipation
  • Inability to keep food or fluids down

How Long Does Hyperemesis Gravidarum Last?

According to ACOG, symptoms of HG typically crop up around nine weeks into pregnancy and tend to subside around the 14-week mark, though sometimes they last longer. Rarely HG can continue through an entire pregnancy.

Morning Sickness vs. Hyperemesis Gravidarum: What’s the Difference?

The main difference between morning sickness and HG is the severity of the symptoms. For example, you may experience nausea and vomiting feel with morning sickness, but these symptoms don't usually cause complications and most people are able to keep food and drink down for most of the day. Morning sickness tends to resolve after the first few months of pregnancy.

Hyperemesis gravidarum, on the other hand, is extreme morning sickness. You may vomit so much that you lose weight and become dehydrated. According to the March of Dimes, the following characteristics distinguish HG from morning sickness:

  • Vomiting more than a few times a day
  • Feeling dizzy after vomiting
  • Becoming dehydrated
  • Losing more than 10 pounds

Unlike morning sickness, which generally resolves by the second trimester, HG may persist well into your second trimester or even throughout your pregnancy.

Possible Complications From HG in Pregnancy

People with HG can be at high risk for complications. According to 2021 research, the most frequent reasons for HG hospital admission include the following:

  • Weight loss (greater than 5% of pre-pregnancy weight)
  • Ketonuria (high levels of ketones in the urine)
  • Dehydration
  • Electrolyte imbalance
  • Acid-base imbalances
  • Irregular heart rhythms

When people get this sick, the biggest medical concern is dehydration and electrolyte imbalance. Most often, the fetus is not affected by HG.

Katherine Hicks, M.D., an OB-GYN who practices in Northampton, Massachusetts, says she has always been amazed at the ability of the fetus to thrive despite the horrendous symptoms the gestational parent experiences. "The babies are almost always a healthy size—sometimes big!"

According to ACOG, however, if a gestational parent can not keep anything down throughout their pregnancy, it can sometimes affect the fetus' size at birth.

Fortunately, people with hyperemesis gravidarum in the early stages of pregnancy don't face a higher risk of miscarriage. In fact, morning sickness is usually associated with a healthy pregnancy.

Of course, if you're going days or hours without keeping food or liquids down, you should see a health care provider as you may require hospitalization, replenishment with IV fluids, or medication.

Diagnosing HG While Pregnant

There is no test to diagnose hyperemesis gravidarum, rather HG is diagnosed based on symptoms and medical history. NORD explains that diagnosis is one of exclusion, meaning that a health care provider will rule out other causes of nausea and vomiting before diagnosing hyperemesis gravidarum.

Hyperemesis Gravidarum Treatment Options

Treatment for hyperemesis gravidarum is often based on the severity of the person's symptoms. Health care providers will typically suggest dietary and lifestyle changes such as eating smaller, more frequent meals and avoiding triggers to help patients cope, but often medication is also needed to manage HG symptoms.

The first line of defense is typically a combination of doxylamine (the active ingredient in the sleep aid Unisom) and vitamin B6 or pyridoxine, both of which are generally considered safe during pregnancy. These medications are available separately over-the-counter or combined as a prescription under the brand names Diclegis and Bonjesta.

If the combination of doxylamine and pyridoxine doesn't relieve your symptoms, your health care provider may also talk to you about prescription antiemetics like Zofran (ondansetron), which are drugs that prevent vomiting. Many of these medications are safe to take during pregnancy, while others pose a higher risk. When deciding whether or not to take antiemetics to treat HG, it's important to weigh the risks and benefits.

Surgeon Sarah Ghanta, M.D., explains that if the pregnant person isn't eating at all, there comes a point when both they and the fetus are at risk. If the gestational parent is malnourished, the chances of having problems with the baby go up. "So you weigh that risk against the risk of a drug doing harm," she says. Most people think that as long as the drug isn't being taken frivolously, keeping yourself eating and nourished during pregnancy is best.

Dr. Rubin adds that currently, clinical studies on the potential teratogenic effects (whether it causes increased congenital disabilities) of Zofran are contradictory. "According to the American College of Obstetricians and Gynecologists, the absolute risk to the fetus is low," she says. "However, all medications should be considered only after an individualized assessment of the potential risks and benefits."

If your vomiting is so severe that you become dangerously hydrated, you may need a stay in the hospital for intravenous (IV) hydration. The weird thing about hyperemesis gravidarum is that the more dehydrated you become, the more nauseated you become and the more likely you are to vomit—and perpetuate the cycle. As a result, an essential piece of treatment for severe HG is supporting hydration. If you continue to lose weight while in the hospital, your provider may also recommend a feeding tube to ensure that you and your baby are getting the essential nutrients you need.

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  1. Placenta and appetite genes GDF15 and IGFBP7 are associated with hyperemesis gravidarum. Nature Communications. 2018.

  2. Life‑threatening complications of hyperemesis gravidarum. Experimental and Therapeutic Medicine. 2021.

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