Clinical Review

2022 Update on obstetrics

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Clinical guidance offerings from ACOG on prevention strategies for preterm birth, antepartum fetal surveillance in appropriate patients, and antenatal corticosteroid use in the periviable period



Obstetrical practice saw updates in 2021 to 3 major areas of pregnancy management: preterm birth prevention, antepartum fetal surveillance, and the use of antenatal corticosteroids.

Updated guidance on predicting and preventing spontaneous PTB

American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins–Obstetrics. Prediction and prevention of spontaneous preterm birth: ACOG practice bulletin, number 234. Obstet Gynecol. 2021;138:e65-e90.

Preterm birth (PTB) continues to pose a challenge in clinical obstetrics, with the most recently reported rate of 10.2% in the United States.1 This accounts for almost 75% of perinatal mortality and more than half of neonatal morbidity, in which effects last well past the neonatal period. PTB is classified as spontaneous (following preterm labor, preterm prelabor rupture of membranes, or cervical insufficiency) or iatrogenic (indicated due to maternal and/or fetal complications).

Assessing risk for PTB

The single strongest predictor of subsequent PTB is a history of spontaneous PTB. Recurrence risk is further increased by the number of prior PTBs and the gestational age at prior PTB. Identification of and intervention for a short cervix has been shown to prolong gestation. Transvaginal ultrasonography of the cervix is the most accurate method for evaluating cervical length (CL). Specific examination criteria exist to ensure that CL measurements are reproducible and reliable.2 A short CL is generally defined as a measurement of less than 25 mm between 16 and 24 weeks’ gestation.

Screening strategies

The American College of Obstetricians and Gynecologists (ACOG), with an endorsement from the Society for Maternal-Fetal Medicine (SMFM), recommends cervical evaluation during the anatomy ultrasound exam between 18 0/7 and 22 6/7 weeks’ gestation in all pregnant patients regardless of prior PTB.3 If transabdominal imaging is concerning for a shortened cervix, transvaginal ultrasonography should be performed to assess the CL.

Serial transvaginal CL measurements are recommended between 16 0/7 and 24 0/7 weeks’ gestation for patients with a current singleton pregnancy and history of a spontaneous PTB, but not for patients with a history of iatrogenic or indicated PTB.

Interventions: Mind your p’s and c’s

Interventions to reduce the risk of spontaneous PTB depend on whether the current pregnancy is a singleton, twins, or higher-order multiples; CL measurement; and history of spontaneous PTB. Preconception optimization of underlying medical conditions also is important to reduce the risk of recurrent indicated PTB.

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