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 doctor what you can do to reduce your risk.

Non-white women under the 18 years or over 35 years have an increased risk of preterm labor. Other factors that may increase your risk include:

Current and past pregnancy:

  • A previous preterm birth
  • Pre-eclampsia
  • Placental abruption
  • Premature rupture of the membranes
  • Vaginal bleeding after 16 weeks, or during more than 1 trimester
  • Being pregnant with a single fetus after in vitro fertilization (IVF)
  • Less than 6 months between giving birth and the beginning of the next pregnancy
  • Presence of a retained intrauterine device
  • History of 1 or more spontaneous second-trimester abortions
  • Too much or too little fluid in the amniotic sac surrounding the baby
  • Surgery on your abdomen during pregnancy

Fetal causes:

  • Carrying more than 1 baby
  • Intrauterine growth delay
  • Birth defects in the baby

Risky behaviors:

History of reproductive organ problems:

  • Uterine fibroids
  • Abnormally shaped uterus
  • Incompetent cervix—the cervix dilates too early in the pregnancy
  • Infection in the cervix, uterus, or vagina
  • Amniotic fluid infection
  • Procedures to remove abnormal cervical cells
  • Urinary tract infections
  • Sexually transmitted infections
  • 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. DES has not been used since the 1970s.

Social causes:

  • Low socioeconomic status
  • Lack of prenatal care
  • Lack of social support

Physical and psychological causes:

  • Being underweight or obese prior to pregnancy
  • A previous bariatric surgery
  • Physical, sexual, or emotional abuse
  • Severe depression or anxiety
  • Diabetes
  • High blood pressure
  • Clotting disorders
  • Certain medications

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