What are the key ultrasound criteria for diagnosing intrauterine growth restriction (IUGR) in a pregnant patient?

Key ultrasound criteria to diagnose intrauterine growth restriction (IUGR) include:

• Estimated fetal weight (EFW) below the 10th percentile for gestational age, based on biometric parameters such as head circumference, abdominal circumference, and femur length.
• Abdominal circumference (AC) measurement is particularly important, as a small AC is a sensitive marker of fetal growth restriction.
• Doppler ultrasound assessment of umbilical artery blood flow is critical; abnormal Doppler findings such as increased resistance or absent/reversed end-diastolic flow indicate placental insufficiency associated with IUGR.
• Assessment of amniotic fluid volume, typically by measuring the deepest vertical pocket (DVP), with oligohydramnios (reduced fluid) supporting the diagnosis of IUGR.
• Serial ultrasound scans to monitor fetal growth velocity and weight discordance, especially in multiple pregnancies, help confirm growth restriction.

In clinical practice, symphysis-fundal height measurements guide the need for ultrasound but are not diagnostic alone. Ultrasound is offered when fundal height is small for gestational age or when other clinical concerns arise NICE NG201. The Royal College of Obstetricians and Gynaecologists recommends using multiple biometric parameters and Doppler studies to assess fetal wellbeing and growth NICE NG201.

Recent international guidelines and literature emphasize the integration of biometric measurements with Doppler velocimetry for a comprehensive assessment. The Society for Maternal-Fetal Medicine and ISUOG guidelines highlight that EFW below the 10th percentile combined with abnormal umbilical artery Doppler is the most reliable indicator of true IUGR rather than constitutionally small fetuses Society for Maternal-Fetal Medicine 2020Salomon et al. 2019. They also recommend serial growth assessments to detect slowing growth velocity, which is a hallmark of IUGR Unknown 2021.

Therefore, the diagnosis of IUGR relies on ultrasound criteria including low estimated fetal weight (<10th percentile), small abdominal circumference, abnormal umbilical artery Doppler flow, and reduced amniotic fluid volume, supported by serial growth monitoring NICE NG201; Society for Maternal-Fetal Medicine 2020Salomon et al. 2019Unknown 2021.