Preterm Birth

Preterm birth is when a baby is born too early, before 37 weeks of pregnancy have been completed. In 2021, preterm birth affected about 1 of every 10 infants born in the United States. The preterm birth rate rose 4% in 2021, from 10.1% in 2020 to 10.5% in 2021. However, racial and ethnic differences in preterm birth rates remain. In 2021, the rate of preterm birth among African-American women (14.8%) was about 50 percent higher than the rate of preterm birth among white or Hispanic women (9.5% and 10.2% respectively).

A developing baby goes through important growth throughout pregnancy─ including in the final months and weeks. For example, the brain, lungs, and liver need the final weeks of pregnancy to fully develop. Read Your Baby Grows Throughout Your Entire Pregnancy [PDF-312KB]. Babies born too early (especially before 32 weeks) have higher rates of death and disability. In 2020 [PDF – 176 KB], preterm birth and low birth weight accounted for about 16% of infant deaths (deaths before 1 year of age). Babies who survive may have

Breathing problems
Feeding difficulties
Cerebral palsy
Developmental delay
Vision problems
Hearing problems

Preterm births may also take an emotional toll and be a financial burden for families.

Frequently Asked Questions: For Women and Their Families

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

If you think you are experiencing preterm labor, it is important that you see a healthcare provider right away. If you are having preterm labor, your provider may be able to give you medicine so that the baby will be healthier at birth.

infographic: some factors associated with preterm birth

[PDF - 561 KB]

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. This preterm birth infographic [PDF – 561 KB] gives some examples of these factors by medical and pregnancy conditions, behavioral factors, and social, personal, and economic characteristics. Talk with your doctor about signs of preterm labor and what to do.

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

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

Behavioral
Tobacco use
Substance use
Stress

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

Another step women and their partners can take to reduce the risk of preterm birth is waiting at least 18 months between pregnancies.

Women who conceive through ART are at higher risk for preterm birth, primarily because they are more likely to be pregnant with more than one baby at a time. More detailed information on ART and preterm birth can be found at Single Embryo Transfer.

Your baby grows throughout your entire pregnancy

[PDF - 2 MB]

Important growth and development occur throughout pregnancy—all the way through the final few weeks. Unless there is a medical need, delivery should not be scheduled before 39 weeks of pregnancy. Read: Your Baby Grows Throughout Your Entire Pregnancy [PDF – 2 MB].

What is CDC’s Division of Reproductive Health doing to prevent preterm birth?

CDC’s Division of Reproductive Health is engaged in a variety of research and science to practice activities aimed at understanding and reducing preterm birth. CDC scientists are collaborating with many partners, including state health departments, university researchers, and other health care professionals to understand why preterm births occur and what can be done to help prevent them. Read about our preterm birth activities.