There is substantial evidence that smoking increases the risk of miscarriage: the Royal College of Physicians has estimated that the risk is increased by 25 per cent.
Smoking during pregnancy is an important cause of ill-health for both mother and foetus. Besides increasing the mother's risk for potentially serious complications, smoking during pregnancy is the largest preventable cause of foetal and infant ill health and death.
For example: one study of almost 60,000 women in Canada found a clear dose response, with the risk of miscarriage increasing with the number of cigarettes smoked. An increased risk was seen even amongst women smoking nine cigarettes or fewer daily.
In a study of nearly 1,300 Japanese women with a past pregnancy, researchers found that those who smoked heavily early in pregnancy were more than twice as likely as non-smokers to suffer a miscarriage in the first trimester.
There are many reasons for women to quit smoking before becoming pregnant. The habit has been linked to increased risks of stillbirth, preterm delivery and low birth weight.