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Ultrasound screening protocol for monitoring monochorionic multifetal pregnancies

Ultrasound screening protocol for monitoring monochorionic multifetal pregnancies
Gestational age Purpose of ultrasound examination and frequency
11 to 14 weeks
  • One examination for:
    • Assessment of gestational age and estimated date of delivery
    • Assessment of chorioamnionicity
    • Measurement of nuchal translucency*
16 AND 18 weeks
  • Fetal size
  • Early fetal anatomic survey, including presence and size of fetal bladders
  • MVP of amniotic fluid
  • Doppler measurement of MCA-PSV
  • Doppler measurement of end-diastolic velocity in the UA
  • Assessment for PDE
20 weeks
  • Fetal size
  • Detailed fetal anatomic survey, including presence and size of fetal bladders
  • MVP
  • Doppler measurement of MCA-PSV
  • Doppler measurement of UA end-diastolic flow velocity
  • PDE
  • Evaluate placental cord insertion sites (proximate cord insertion is defined by a distance between cord insertions below the fifth percentile for gestational age or by 3.3 to 4.0 cm at any gestational age)
20 to 22 weeks
  • Transvaginal ultrasound measurement of cervical length
  • Fetal echocardiogram
22 to 32 weeks
  • Serial examinations of fetal growth every 4 weeks
  • Serial examinations of the following every 2 weeks:
    • MVP
    • Presence and size of fetal bladders
    • Doppler measurement of MCA-PSV
    • Doppler measurement of UA end-diastolic flow velocity
    • PDE
32 to 36 weeks
  • Continue serial examinations of fetal growth every 4 weeks
  • Weekly examinations:
    • Biophysical profile score
    • Doppler measurement of MCA-PSV
    • Doppler measurement of UA end-diastolic flow velocity
    • PDE
MVP: maximum vertical pocket; MCA: middle cerebral artery; PSV: peak systolic velocity; UA: umbilical artery; PDE: placental discordance echogenicity.
* Increased nuchal translucency has been associated with trisomy 21, a variety of congenital anomalies, developmental and genetic syndromes, and twin-twin transfusion syndrome. Refer to UpToDate content on cystic hygroma and increased nuchal translucency.
Modified from:
  1. Khalil A, Rodgers M, Baschat A, et al. ISUOG Practice Guidelines: role of ultrasound in twin pregnancy. Ultrasound Obstet Gynecol 2016; 47:247.
  2. Society for Maternal-Fetal Medicine, Simpson LL. Twin-twin transfusion syndrome. Am J Obstet Gynecol 2013; 208:3.
  3. Sueters M, Middeldorp JM, Lopriore E, et al. Timely diagnosis of twin-to-twin transfusion syndrome in monochorionic twin pregnancies by biweekly sonography combined with patient instruction to report onset of symptoms. Ultrasound Obstet Gynecol 2006; 28:659.
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