Risk factors are things that may make it more likely that your child will get attention deficit hyperactivity disorder (ADHD). But it's important to realize that having a risk factor does not mean your child will definitely get ADHD. We know only that children who have ADHD are more likely to have these things.

• Family history: A tendency to get ADHD can be passed on through families. If one member of your family has ADHD, then there is a greater chance that another member also will have it.¹
• Smoking d ur ing pregnancy: Mothers of children with ADHD are more likely to have smoked during their pregnancy than mothers of children without ADHD. One study estimated that smoking during pregnancy raised the risk of having a child with ADHD by around a third.¹
• Lo w birth weight: If your child's weight at birth was below average, then he or she has a greater chance of getting ADHD. For every four or five newborns weighing less than 52.5 ounces (about 3 pounds, 4 ounces), one will go on to develop ADHD. However, less than 1 in 10 children born at a normal weight will develop the condition.
• Having surgery within the first month of life: This raises a child's risk, but only slightly.^{1 2}

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.