A risk factor is something that increases your likelihood of getting a disease or condition.

It is possible to have preterm labor with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of having preterm labor. If you have a number of risk factors, ask your healthcare provider what you can do to reduce your risk.

Risk factors for preterm labor include:

  • A previous preterm birth
  • Low socioeconomic status
  • Non-white race
  • Age less than 18 or greater than 35 years
  • Premature rupture of the membranes
  • Carrying more than one baby
  • History of one or more spontaneous second-trimester abortions
  • Risky behaviors:
    • Smoking
    • Illicit drug use
    • Alcohol use
    • Lack of prenatal care
  • Uterine problems:
    • Fibroids —This is a benign tumor in the wall of the uterus.
    • Abnormally shaped uterus—This does not allow enough space for the baby to grow.
    • Incompetent cervix—The cervix dilates too early in the pregnancy.
    • Exposure to diethylstilbestrol (DES)—Before its dangers were known, DES was given to pregnant women to decrease the risk of miscarriage; if your mother took DES while she was pregnant with you, your reproductive organs may be damaged
  • Infections:
    • Amniotic fluid infection
    • Urinary tract infections (including kidney or bladder)
    • Infection in the cervix, uterus, or vagina
    • Sexually transmitted infections, such as trichomoniasis
  • Fetal causes:
    • Intrauterine fetal death
    • Intrauterine growth retardation
    • Birth defects in the baby
  • Placental abruption (early separation of the placenta from the wall of the uterus)
  • Presence of a retained intrauterine device
  • Being underweight or obese prior to pregnancy
  • Poor eating habits
  • Physical, sexual, or emotional abuse
  • Lack of social support
  • Stress
  • Working long hours with long periods of standing and/or doing physically strenuous work
  • Less than six months between giving birth and the beginning of the next pregnancy
  • Diabetes
  • High blood pressure
  • Pre-eclampsia (a combination of high blood pressure, water retention, and protein in the urine)
  • Clotting disorders (thrombophilia)
  • Vaginal bleeding after 16 weeks, or during more than one trimester
  • Being pregnant with a single fetus after in vitro fertilization (IVF)
  • Too much or too little fluid in the amniotic sac surrounding the baby
  • Surgery on your abdomen during pregnancy, such as removal of the appendix
  • Hormonal imbalance