Preterm birth is when a baby is born too early, before 37 weeks of pregnancy have been completed. In 2016, preterm birth affected about 1 of every 10 infants born in the United States. Preterm birth rates decreased from 2007 to 2014, and CDC research shows that this decline is due, in part, to declines in the number of births to teens and young mothers. However, the preterm birth rate rose for the second straight year in 2016. Additionally, racial and ethnic differences in preterm birth rates remain. For example, in 2016, the rate of preterm birth among African-American women (14%) was about 50 percent higher than the rate of preterm birth among white women (9%).

Premature Birth


In most cases, preterm labor (labor that happens too soon, before 37 weeks of pregnancy) begins unexpectedly and the cause is unknown. Like regular labor, signs of early labor are—

  • Contractions (the abdomen tightens like a fist) every 10 minutes or more often
  • Change in vaginal discharge (a significant increase in the amount of discharge or leaking fluid or bleeding from the vagina)
  • Pelvic pressure—the feeling that the baby is pushing down
  • Low, dull backache
  • Cramps that feel like a menstrual period
  • Abdominal cramps with or without diarrhea

Many times we do not know what causes a woman to deliver early, but several known factors may increase the likelihood that a woman could deliver early.

Social, Personal, and Economic Characteristics
Teens and women over age 35
Black race
Women with low income

Pregnancy and Medical Conditions
Prior preterm birth
Carrying more than 1 baby (twins, triplets, or more)

Tobacco use
Substance use


Preventing preterm birth remains a challenge because there are many causes of preterm birth, and because causes may be complex and not always well understood. However, pregnant women can take important steps to help reduce their risk of preterm birth and improve their general health. These steps are to—

  • Quit smoking. For help quitting, see How to Quit Smoking
  • Avoid alcohol and drugs
  • Get prenatal care as soon as you think you may be pregnant and throughout the pregnancy
  • Seek medical attention for any warning signs or symptoms of preterm labor
  • Talk with your doctor or other healthcare provider about the use of progesterone treatment if you had a previous preterm birth