Hyperemesis gravidarum is the medical term for extreme, persistent nausea and vomiting; significant weight loss (more than five per cent of pre-pregnancy weight); and dehydration during pregnancy. It’s much worse than morning sickness, making daily activities impossible and often requiring admission to the hospital for care.

Up to 80 per cent of pregnant women have some degree of nausea, usually worse when first awakening in the morning that is termed “morning sickness”: the nausea is mild to moderate; there is occasional vomiting; and the woman can keep some food and fluids down. Most often it’s gone by the end of the first trimester (about 12 weeks into the pregnancy) but it can persist throughout. Management may involve wearing acupressure wristbands; eating ginger chews and drinking ginger teas; and small, frequent meals (approximately every two hours) of bland, dry food (for example: crackers, toast, white potatoes or rice).

Foods that are high in fat, greasy and/or spicy can make things worse. If needed, a medication called Diclectin is prescribed, which is a combination of an antihistamine (doxylamine) with a form of Vitamin B6 (pyridoxine). If certain foods seem to trigger symptoms, they can be avoided. For many women these changes work.

Sometimes, however (in 0.3 — 10.8 per cent of pregnancies), the nausea and vomiting can’t be controlled. There is constant, severe nausea; vomiting multiple times a day; an inability to keep liquids or solids down; eventually causing lightheadedness (dizziness), and extreme fatigue. The woman may even lose weight rather than gain. This puts both her and the baby at risk. This is true HG and to manage it the woman is often admitted to the hospital to intravenously replace the fluids and control her nausea. Fortunately for most women, even if it lasts the entire pregnancy (which it may not), once the baby is delivered the condition quickly resolves.

We now have a better idea of what causes HG in at least some cases. GDF 15 is a hormone that is normally made by the placenta. Some women have low levels of this hormone before they become pregnant and become very sensitive to the higher levels that they develop during the normal course of the pregnancy. The hormone triggers nausea and vomiting through its effect on a specific trigger zone in the brain.

There are known HG risk factors including: 1) carrying twins or triplets; 2) a first pregnancy; 3) having had HG in a previous pregnancy; 4) a history of motion sickness, migraines, menstrual pain and/or nausea before the period or difficulty tolerating the oral contraceptive; 5) being overweight (more than 170 lbs or 77 kg); 6) a positive family history of HG; 7) having gestational trophoblastic disease which involves abnormal cell growth in the uterus.

When should a pregnant women seek medical care since nausea and vomiting can be a regular and normal part of a pregnancy? Certainly, if you’re unable to drink for more than eight hours or eat for more than 24 hours; feeling dizzy or lightheaded; not urinating as often as you were and having urine that’s dark. Any of these is already enough of a reason to seek medical care.

To be clear: with morning sickness you should be able to eat and drink at some point during the day. With HG you often can’t. With morning sickness, you have nausea and occasional vomiting. With HG the nausea is almost constant, and the vomiting is repetitive during the day. Don’t wait for the symptoms to become full blown. If in doubt, talk to a health care professional earlier rather than later.

Faith could save you — and we're not just talking about your soul!

Learn about the science behind the importance of belonging (and community) with Dr. Mitch Shulman, who'll be speaking at the Dorshei Emet synagogue, 18 Cleve Road in Hampstead, on Monday, Sept. 21 starting at 4 p.m. You can attend in person or online. Find out what science can — and cannot — tell us about faith, belief and our health. For more information and to get tickets, visit dorsheiemet.com

Dr. Mitch Shulman is an Associate Professor in the Department of Emergency Medicine at McGill Medical School as well as an Attending Physician in the Emergency Department of the McGill University Health Centre. He’s also the CJAD AM 800 Medical Consultant.