The following are risk factors for increased risk of premature labor and premature births.

1. Carrying twins, triplets, or other multiples
2. Short cervix
3. Genital-tract infections
4. Having little or no prenatal care
5. Previous preterm labor or birth
6. Preterm labor or warning signs during this pregnancy
7. Carrying a fetus with anomalies
8. Having too much amniotic fluid
9. A history of more than one second-trimester induced abortion
10. An abnormal cervix (after conization surgery, for example)
11. An abnormal uterus (bicornuate uterus, fibroids)
12. Placenta previa (placenta covering the cervix)
13. Smoking cigarettes or using cocaine
14. Maternal DES exposure as a fetus
15. Short interpregnancy intervals (less than 18 month and more than 59 months)
16. Working long hours; work-related fatigue; standing for prolonged periods
17. Abdominal surgery during the current pregnancy
18. Serious infection or bleeding during the current pregnancy
19. Being underweight or weighing less than 100 pounds (BMI under 19)