Sashaying down the stage in a green gown and black Jimmy Choos, her skin glowing and chestnut locks bouncing around, Kate Middleton stunned the audience at an awards function in London on Monday. The Duchess of Cambridge must have hired a brilliant stylist considering she looked so resplendent despite her debilitating condition - she was recently hospitalised with hyperemesis gravidarum (HG) or severe pregnancy-related morning sickness.

Women with this form of unrelenting nausea and vomiting usually spend their pregnancies looking, and feeling, terrible. "My skin had become pale, my eyes sunken and my hair lifeless. I used to look in the mirror and wonder where that glow I had heard about was, " says Gunjan Goyal, mommy to an eight-month-old.

While 70 per cent of pregnant women suffer from nausea in the first trimester, HG affects less than one per cent. For this unfortunate bunch, the retching does not end by the fourth monthmark, nor is it confined to the mornings. "It should be called day-long sickness. I used to throw up 10 or 20 times, mostly in the evenings, " says Neeti Dagli, a Bangalore-based media professional who has a five-year-old daughter. Her suffering did not qualify as hyperemesis - women with HG lose five per cent of their pre-pregnancy body weight - but it was still acute enough to leave a terrible, and metallic, taste in her mouth.

"I used to push food down by distracting myself with TV. My husband used to work night shifts and I'd be alone at home, feeling miserable and force-feeding myself, " she says.

Goyal recalls with horror how she had to stop her car on a flyover to puke out her lunch, lean over the office toilet countless times and, worse still, clean it so colleagues could use the loo without getting nauseous, too. "Anything could trigger it. The very sight and smell of food made me feel sick. I remember my husband just said the word 'sausage' and I had to rush to the bathroom, " recalls Goyal. In a recent blog post empathising with Middleton, an HG sufferer, Luschka, notes that HG is like "being so hungover you can't even keep water in your body. And it's like that 24/7 for however long it lasts. "

Forget eating for two, HG sufferers find it difficult to even keep a sip of water down and sometimes land up in the hospital with dehydration. "A few of my patients had to be hospitalised multiple times during their pregnancies and put on intravenous fluids, " says Dr Manjit Kochar, senior obstetrician at Fortis La Femme hospital in Delhi. It is important to keep the mother hydrated so she does not become malnourished.

HG is believed to be caused by higher-thannormal levels of the pregnancy hormone, human chorionic gonadotropin or HCG. Women carrying more than one foetus are therefore more prone to it. Middleton's hospitalisation has therefore sparked a rumour that she is set to give birth to twin heirs. A recent study also suggests that women with hyperemesis are more likely to have a baby girl but there is very little evidence to support this hypothesis.

Doctors point out that extreme morning sickness is also more common among older women and those with molar pregnancies. Such pregnancies are not viable as they mean that the woman is carrying a foetus with abnormal DNA or benign growth. "It is also important to rule out gall bladder stones and liver disorders as they too may be associated with hyperemesis, " says Kochar.

HG is diagnosed after running a simple urine test to check for the presence of ketones - substances produced if the body is forced to break down fat for energy due to lack of nourishment.

Prior to the availability of IV therapy in the 1950s, HG was a major cause of maternal mortality. Jane Eyre author Charlotte Bronte who is believed to have died from HG four months into her pregnancy in 1955, wrote: "Let me speak the plain truth. . . my sufferings are very great. . . my nights indescribable. . . sickness with scarce a reprieve. . . I strain until what I vomit is mixed with blood. "

A year after the novelist's death, Thalidomide, a drug developed as a mild sleeping pill and morning sickness remedy, became available over the counter in Europe and was an instant hit with expectant mothers. But it had disastrous side effects. Babies were born with shortened limbs, blindness, deafness, heart problems and brain damage. By 1962 it was established that thalidomide was responsible for disabilities in over 10, 000 children.

The 'Thalidomide disaster' made the medical community even more reluctant to prescribe drugs during pregnancy and left countless women miserable. "My gynaecologist told me to just 'sip lemonade and live with it', " says Sheebani Banga, who suffered chronic morning sickness during her first pregnancy in 1983.

Fortunately for the Duchess, the scenario has changed. Several anti-emitic drugs like Ondansetron and an antihistamine-vitamin B6 combination - Doxylamine Succinate with Pyridoxine - have been proven safe and effective in putting an end to the vomiting without posing any risk to the foetus. "But we prescribe these medicines only when natural remedies like ginger or lemon drops fail. We also suggest oral rehydrants like Electrol, Enerzal and energy drinks like Glucon D, " says Dr Kiran Coelho, who heads Lilavati' hospital's gynaecology department.

Morning sickness usually does not have any adverse effect on the baby. Some studies have in fact shown that women suffering from it are less likely to miscarry. But it could increase the risk of intra-uterine growth restriction resulting in a low birth weight. Sufferers may also have to battle prenatal depression.