Preterm Labor: Prevention and Management

 

In the United States, preterm delivery is the leading cause of neonatal morbidity and is the most common reason for hospitalization during pregnancy. The rate of preterm delivery (before 37 weeks' gestation) has been declining since 2007. Clinical diagnosis of preterm labor is made if there are regular contractions and concomitant cervical change. Less than 10% of women with a clinical diagnosis of preterm labor will deliver within seven days of initial presentation. Women with a history of spontaneous preterm delivery are 1.5 to two times more likely to have a subsequent preterm delivery. Antenatal progesterone is associated with a significant decrease in subsequent preterm delivery in certain pregnant women. Current recommendations are to prescribe vaginal progesterone in women with a shortened cervix and no history of preterm delivery, and to use progesterone supplementation regardless of cervical length in women with a history of spontaneous preterm delivery. Cervical cerclage has been used to help correct structural defects or cervical weakening in high-risk women with a shortened cervix. A course of corticosteroids is the only antenatal intervention that has been shown to improve postdelivery neonatal outcomes, including a reduction in neonatal mortality, intracranial hemorrhage, necrotizing enterocolitis, and neonatal infection. Tocolytics, especially prostaglandin inhibitors and calcium channel blockers, may allow time for the administration of antenatal corticosteroids and transfer to a tertiary care facility if necessary. When used in specific at-risk populations, magnesium sulfate provides neuroprotection and decreases the incidence of cerebral palsy in preterm infants.

Spontaneous preterm delivery is the leading cause of neonatal morbidity in the United States and is the most common reason for hospitalization during pregnancy. The rate of all-cause preterm deliveries in the United States decreased from 10.4% in 2007 to 9.6% in 2015. In 2014, preterm deliveries occurred in 7.7% of single gestation pregnancies.1 Multiple gestation pregnancies are associated with increased rates of preterm delivery (50% of twins and 90% of triplets are delivered before 37 weeks' gestation).2 Preterm delivery (birth before 37 weeks' gestation) is further delineated into very early preterm (before 32 weeks), early preterm (32 0/7 to 33 6/7 weeks), and late preterm (34 0/7 to 36 6/7 weeks).

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SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferences

In women with a single gestation pregnancy and a history of spontaneous preterm delivery, progesterone supplementation is beneficial starting at 16 to 24 weeks' gestation and continuing through 34 weeks' gestation.

A

3, 12, 2325

Once preterm labor is confirmed, a single course of corticosteroids (betamethasone or dexamethasone) is the only intervention for improving neonatal outcomes. It is recommended between 24 and 34 weeks' gestation and may be considered as early as 23 weeks' gestation.

A

21, 37

Antenatal magnesium sulfate provides neuroprotection, decreasing the risk of cerebral palsy in infants born at less than 32 weeks' gestation.

B

3841

Tocolytics, such as prostaglandin inhibitors and calcium channel blockers, should be used to prolong the time to delivery so that antenatal corticosteroids and potentially magnesium sulfate can be administered, and the mother can be transferred to a tertiary facility with a neonatal intensive care unit.

A

21, 41


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to http://www.aafp.org/afpsort.

SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingReferences

In women with a single gestation pregnancy and a history of spontaneous preterm delivery, progesterone supplementation is beneficial starting at 16 to 24 weeks' gestation and continuing through 34 weeks' gestation.

A

3, 12, 2325

Once preterm labor is confirmed, a single course of corticosteroids (betamethasone or dexamethasone) is the only intervention for improving neonatal outcomes. It is recommended between 24 and 34 weeks' gestation and may be considered as early as 23 weeks' gestation.

A

21, 37

Antenatal magnesium sulfate provides neuroprotection, decreasing the risk of cerebral palsy in infants born at less than 32 weeks' gestation.

B

3841

Tocolytics, such as prostaglandin inhibitors and calcium channel blockers, should be used to prolong the time to delivery so that antenatal corticosteroids and potentially magnesium sulfate can be administered, and the mother can be transferred to a tertiary facility with a neonatal intensive care unit.

A

21, 41


A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice,

The Authors

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KRISTEN RUNDELL, MD, is a visiting associate professor in the Department of Family Medicine at The Ohio State University Wexner Medical Center in Columbus....

BETHANY PANCHAL, MD, is an assistant professor in the Department of Family Medicine at The Ohio State University Wexner Medical Center.

Address correspondence to Kristen Rundell, MD, The Ohio State University College of Medicine, 2231 North High St., Columbus, OH 43201 (e-mail: kristen.rundell@osumc.edu). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

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