Britain's Catherine, Duchess of Cambridge made headlines recently when news of her pregnancy broke after she was admitted to hospital suffering from acute morning sickness. Morning sickness is an unwelcome side effect that can detract from the joy of pregnancy.
"Nausea and vomiting are one of the most common side effects of early pregnancy, affecting 70 to 80 per cent of all pregnant woman," says Dr Julia Dresel of the Kandang Kerbau Women's and Children's Hospital in Singapore. "The expression 'morning sickness' is misleading, since it is not a real sickness, but a feeling of nausea that can last throughout the whole day."
The degree of nausea and vomiting varies widely between women, and as in the duchess' case, can be so severe that it warrants a stay in hospital. While severe morning sickness occurs in women carrying both boys and girls, it is commonly associated with women carrying girls or multiple fetuses.
Severe morning sickness, or hyperemesis gravidarum, is defined by the loss of at least 5 per cent of total body weight and affects about one in 200 to 500 pregnant women. Weight loss occurs because of frequent vomiting and the inability to keep down food and liquids, leading to dehydration and malnutrition.
The condition can lead to medical complications and should be rapidly treated with anti-sickness medication and intravenous hydration. Before the introduction of intravenous treatment in the 1950s, severe morning sickness could prove fatal to both mother and fetus.
One rare complication that can arise is a neurological disorder known as Wernicke's encephalopathy. This occurs because of a lack of vitamin B1. Women who are admitted to hospital for severe morning sickness are typically given supplementation of this vitamin and electrolytes through intravenous hydration. Causes of morning sickness remain poorly understood but it is believed that several factors are involved.
One theory points towards high levels of the pregnancy hormone human chorionic gonadotropin that peaks during the first trimester, before falling after week 12. This hormonal change at the early stage of pregnancy coincides with the time when symptoms of morning sickness predominantly appear.