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Am Fam Physician. 2022;106(3):337-339

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial relationships.

Key Points for Practice

• Preterm birth rates can be reduced by ceasing tobacco and alcohol use, increasing contraception access, and increasing interpregnancy intervals to at least 18 months.

• Daily vaginal progesterone starting between 20 and 24 weeks until 34 weeks’ gestation can reduce preterm birth risk for patients with cervical shortening or a history of preterm birth.

• When a visually dilated cervix is identified, cervical cerclage therapy increases pregnancy duration and improves neonatal survival.

From the AFP Editors

Preterm birth, or delivery occurring between 20 and 37 weeks' gestation, may be spontaneous or due to a maternal or fetal complication. Early preterm birth occurs up to 34 weeks' gestation, and late preterm birth occurs between 34 and 37 weeks' gestation. Preterm births account for one in 10 deliveries, and 3% of births are early preterm. The American College of Obstetricians and Gynecologists (ACOG) has new recommendations for predicting and preventing preterm birth.

Risk Factors

All pregnant patients are at risk for preterm birth, and one in 20 nulliparous patients will deliver preterm. Many risk factors for preterm birth are unmodifiable. Multiple pregnancies confer the highest risk, with preterm births occurring in 60% of twin pregnancies and 98% of triplet pregnancies.

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Coverage of guidelines from other organizations does not imply endorsement by AFP or the AAFP.

This series is coordinated by Michael J. Arnold, MD, Assistant Medical Editor.

A collection of Practice Guidelines published in AFP is available at

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