We don’t really know what causes hyperemesis gravidarum (HG), but it is believed to be related to the rise of hormone levels associated with pregnancy. Whatever the cause, this disorder can be extremely unpleasant and even dangerous - symptoms include nausea and vomiting so severe that women can’t keep food and fluids down. This inability to eat and drink can result in weight loss (from five to 20 pounds) and a disturbance of electrolytes. In the worst cases, women report dizziness, fainting, weakness, and vomiting blood; the resulting dehydration and nutritional deficiencies may lead to kidney and liver failure. Kate Middleton’s case apparently was serious enough to require a stay in the hospital and intravenous fluids.
HG itself is relatively rare, and not every pregnant woman with this condition requires hospitalization – most cases are treated on an outpatient basis with dietary changes, rest, and antacids. Obviously, HG is much more serious than common morning sickness, which afflicts up to 80 percent of pregnant women and usually subsides at the end of the first trimester.
According to the American Pregnancy Association, the symptoms of HG usually appear between four and six weeks of pregnancy and may ease off after 13 weeks. However, as many as 20 percent of women diagnosed with HG may suffer from the condition throughout their entire pregnancies. A study published in 2010 by the U.S. Agency for Healthcare Research and Quality found that, in the U.S., HG affects between 0.5 and 2.0 percent of pregnant women annually and accounts for more than 285,000 hospitalizations per year. Babies born to mothers who have suffered with prolonged HG may also have serious problems, including low birth weight or being born preterm. In rare cases, HG leads to fetal or neonatal death.
There is no known way to prevent hyperemesis gravidarum. Research suggests that risks of the condition may be higher among women who are overweight, have allergies, become pregnant at a young age, or have been on some type of restrictive diet. Being lactose intolerant or having food sensitivities also appear to increase the risk. Some research has indicated that HG may be autoimmune in nature, but this has not been proved. Over the years, the condition has been attributed to toxins, ulcerations, infection, an abnormality of the reproductive system or abnormal functioning of the esophageal sphincter. In the early years of the 20th century, HG was deemed psychological in nature, a theory that still persists among some medical personnel. Unfortunately, there hasn’t been a lot of research into HG, but current theories hold that the underlying cause is a reaction to increased estrogen levels associated with pregnancy.
Andrew Weil, M.D.