The American College of Obstetricians and Gynecologists (ACOG) and the American Institute of Ultrasound in Medicine have developed a clinical practice bulletin on the importance of obstetric ultrasound. The purpose of the bulletin is to present information and evidence regarding the methodology of, indications for, benefits of, and risks associated with obstetric ultrasonography in specific clinical situations. The following conclusions are based on good and consistent evidence (Level A):
- At various gestational ages, ultrasound examination is an accurate method of determining gestational age, fetal number, viability, and placental location, and it is recommended for all pregnant patients.
- Gestational age is most accurately determined in the first half of pregnancy.
- Measurement of nuchal translucency alone is less effective for first-trimester screening of the singleton pregnancy than is combined testing (nuchal translucency measurement and biochemical markers).
- In a center with trained personnel, Doppler measurement of peak systolic velocity in the fetal middle cerebral artery is an appropriate noninvasive means to monitor pregnancies at risk of fetal anemia.
- Umbilical artery Doppler velocimetry used in conjunction with standard fetal surveillance, such as nonstress tests, biophysical profiles, or both, is associated with improved outcomes in fetuses with fetal growth restriction.
The practice bulletin also offers conclusions based on limited or inconsistent evidence (Level B) and conclusions and recommendations based primary on consensus and expert opinion (Level C), including:
- In the absence of other specific indications, the optimal time for a single ultrasound examination is at 18 to 22 weeks of gestation (Level C).
Ultrasound in pregnancy. Practice Bulletin No. 175. American College of Obstetricians and Gynecologists. Obstet Gynecol. 2016;128:e241–56.
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