Risk factors

Often, the specific cause of premature birth isn't clear. However, there are known risk factors of premature delivery, including:

• Having a previous premature birth
• Pregnancy with twins, triplets or other multiples
• An interval of less than six months between pregnancies
• Conceiving through in vitro fertilization
• Problems with the uterus, cervix or placenta
• Smoking cigarettes or using illicit drugs
• Some infections, particularly of the amniotic fluid and lower genital tract
• Some chronic conditions, such as high blood pressure and diabetes
• Being underweight or overweight before pregnancy
• Stressful life events, such as the death of a loved one or domestic violence
• Multiple miscarriages or abortions
• Physical injury or trauma

For unknown reasons, black women are more likely to experience premature birth than are women of other races. But premature birth can happen to anyone. In fact, many women who have a premature birth have no known risk factors.