• Late or no prenatal care

• Substance abuse, including alcohol, illicit drugs and smoking

• Certain chronic diseases, such as high blood pressure, diabetes and lupus

• Poor nutrition or being overweight or underweight

• Infections, including sexually transmitted diseases

• Age — under 20 or over 40

• Multiple pregnancy (twins, triplets, etc.)

• History of preterm delivery

• Certain uterine or cervical abnormalities

• Stress or lack of emotional support

• Short term between pregnancies — less than six months

• Race — blacks have a higher incidence of preterm births