If you smoke and you're expecting a baby, expect to spend a lot more sleepless nights in the nursery.
A Danish study finds that babies are twice as likely to develop colic - a nightmare for parents - if their mothers smoke heavily.
Researchers in Denmark, where about a third of the population smokes, found that eleven percent of babies studied suffered from colic, but the rate doubled among women who smoked 15 or more cigarettes a day during pregnancy.
The results were the same even when researchers adjusted for other factors such as alcohol consumption, birth weight, the age of the mothers and smoking habits of the fathers. The results appear in the August issue of the journal Paediatrics.
Despite extensive publicity about the hazards of smoking during pregnancy, as many as one in four Danish women smoke while they're expecting, says study co-author Dr Charlotte Sondergaard, an epidemiologist at the University of Aarhus in Denmark.
No one knows what percentage of babies suffer from colic worldwide. The estimates vary from 8 percent to 40 percent, depending on how the number is calculated, Sondergaard says.
As millions of weary parents know, colic is very difficult to stop. It usually begins in the first three weeks of life and ends at three or four months.
Eyzaguirre says, "It will appear suddenly. The baby cries loudly and differently, which a mother can recognise better than anyone else. The crying can last for several hours."
The babies are clearly in intense pain. Their faces turn red. In some a white pallor appears around the lips. They pull their legs in and out, "and they have feet that are cold and hands that are clenched," Eyzaguirre says.
An episode of colic often ends in four or six hours when the baby reaches complete exhaustion, he says.
The many theories about the cause of colic involve gas and pressure in the gastrointestinal system. Some experts think the babies are suffering from hunger, while others suspect they have overeaten. Others point to milk allergies or sensitivity to carbohydrates in cereal or sugar added to milk.
While smoking and colic appear to be linked, no one knows why. Sondergaard says one possibility is that smoking delays the maturation of the central nervous or gastrointestinal systems.
Eyzaguirre says some smokers view cigarettes as a potent laxative, and nicotine may have the similar effect on babies but create cramps instead of relief.
The Danish researchers say the study did not look for a link between colic and smoking by mothers after birth.
What to do
The many ways to treat colic include some that try to expel gas with bouncing movements.
Eyzaguirre recommends taking the baby for a ride in a car or placing him or her on the top of a working washer or dryer. (Make sure a cotton cloth is under the baby, and by all means don't leave the child unattended.)
Smoking not always to blame