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

Nearly all women have some nausea or vomiting, or "morning sickness " -- particularly during the first 3 months of pregnancy. The cause of nausea and vomiting during pregnancy is believed to be rapidly rising blood levels of a hormone called HCG (human chorionic gonadotropin), which is released by the placenta.

Extreme nausea and vomiting during pregnancy can happen if you are pregnant with twins (or more) or if you have a hydatidiform mole.

• Severe, persistent nausea during pregnancy, often leads to weight loss
• Lightheadedness or fainting

The doctor will perform a physical exam. Blood pressure may be low. Pulse may be high.

The following laboratory tests will be done to check for signs of dehydration:

• Hematocrit
• Urine ketones

Your doctor may need to run tests to rule out liver and gastrointestinal problems.

A pregnancy ultrasound will be done to see if you are carrying twins or more, and to check for a hydatidiform mole.

Small, frequent meals and eating dry foods such as crackers may help relieve uncomplicated nausea.

You should drink plenty of fluids. Increase fluids during the times of the day when you feel the least nauseated. Seltzer or other sparkling waters may be helpful.

Vitamin B6 (no more than 100mg daily) has been shown to decrease the nausea in early pregnancy.

Medication to prevent nausea is reserved for cases where vomiting is persistent and severe enough to present potential risks to you and your unborn baby. In severe cases, you may be admitted to the hospital, where fluids will be given to you through an IV.

Nausea and vomiting usually peaks between 2 and 12 weeks of pregnancy and goes away by the second half of pregnancy. With proper identification of symptoms and careful follow up, this condition rarely presents serious complications for the infant or mother.

Too much vomiting is harmful because it leads to dehydration and poor weight gain during pregnancy.

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 have severe nausea and vomiting.

Hepatic and Gastrointestinal Diseases. In: Gabbe SG, Niebyl JR, Simpson JL. Obstetrics - Normal and Problem Pregnancies. 5th ed. New York, NY: Churchill Livingstone; 2007:Chap.43

Interventions for nausea and vomiting in early pregnancy. Cochrane Database Syst Rev. 2003;(4):CD000145. Review.