Hyperemesis gravidarum is extreme, persistent nausea and vomiting during pregnancy that may lead to dehydration.

Nearly all women experience some degree of "morning sickness" -- nausea and vomiting during pregnancy, particularly during the first trimester. The cause of nausea and vomiting during pregnancy is believed to be rapidly rising serum levels of a hormone called HCG (human chorionic gonadotropin) secreted by the fetus. Increased estrogen levels have also been implicated.

However, too much vomiting can interfere with the weight gain needed to sustain the pregnancy and cause dehydration, which can be harmful to both mother and child. Extreme nausea and vomiting during pregnancy may indicate a multiple pregnancy (twins or more) or, extremely rarely, a hydatidiform mole or thyroid disorder.

• Symptoms of pregnancy
• Severe nausea
• Persistent excessive vomiting (often leading to weight loss)
• Lightheadedness or fainting

Signs of dehydration may occur, including:

• Ketones in urine
• Increased hematocrit
• Increased pulse rate
• Decreased blood pressure

Blood tests may be recommended for further evidence of dehydration.

Uncomplicated nausea may be treated with dry foods such as crackers and small, frequent meals.

It is important for a pregnant woman to maintain her fluid intake. Fluids should be increased during the times of the day when the woman feels the least nauseated. Seltzer or other sparkling waters may be helpful.

Medication to prevent nausea is reserved for cases where vomiting is persistent and severe enough to present potential risks to the mother and unborn baby. The most severe cases may require admission to a hospital and IV fluids.

An evaluation to rule out liver or gastrointestinal problems may be needed.

Nausea and vomiting usually peaks between 2 and 12 weeks gestation and resolves by the second half of a pregnancy. With adequate identification of symptoms and careful follow-up, this sickness rarely presents serious complications for the infant or mother.

Social or psychological problems may be associated with this disorder of pregnancy. If such problems exist, they need to be identified and addressed appropriately.

Call your health care provider if you are pregnant and are experiencing severe nausea with vomiting.