From the Guidelines
A fluid and growth ultrasound is performed by measuring key fetal biometric parameters and assessing amniotic fluid levels, with the entire procedure typically taking 20-30 minutes and being painless, as described in the most recent study 1. The procedure begins with the patient lying on an examination table with their abdomen exposed. The sonographer applies a clear gel to the abdomen to enhance sound wave transmission. Using a handheld transducer, the technician moves the device across the abdomen to capture images of the fetus and surrounding structures. During the examination, the sonographer measures key fetal biometric parameters including:
- Head circumference
- Biparietal diameter
- Abdominal circumference
- Femur length to assess fetal growth, as outlined in the study 1. Amniotic fluid is evaluated by:
- Measuring the deepest vertical pocket
- Calculating the amniotic fluid index (AFI) by summing the deepest vertical pockets in four quadrants of the uterus, as described in the study 1. The study 1 highlights the importance of assessing amniotic fluid volumes, which can indicate fetal well-being and proper placental function. Patients should arrive with a moderately full bladder if in early pregnancy (before 20 weeks) to improve visualization. This ultrasound is crucial for:
- Identifying growth abnormalities
- Detecting conditions like intrauterine growth restriction or macrosomia
- Assessing amniotic fluid volumes, as emphasized in the study 1.
From the Research
Procedure for Performing a Fluid and Growth Ultrasound
To perform a fluid and growth ultrasound, the following steps are typically involved:
- Assessment of amniotic fluid volume, which is a routine part of sonographic evaluation of fetal status 2
- Measurement and quantification of amniotic fluid volume using methods such as the four-quadrant amniotic fluid index 3
- Evaluation of fetal growth and development, including measurement of fetal parameters such as abdominal circumference 4
- Assessment of fetal wellbeing using biophysical profile scoring, which includes evaluation of fetal tone, movement, breathing, and heart rate 5, 4
Equipment and Techniques
The following equipment and techniques may be used:
- Ultrasound transducers, such as 3.5-MHz linear, sector, or convex transducers 3
- Doppler ultrasonography to assess fetal blood flow and umbilical artery pulsatility index 4
- Biophysical profile scoring to assess fetal wellbeing 5, 4
Interpretation of Results
The results of the fluid and growth ultrasound are interpreted in the context of fetal wellbeing and growth. Abnormalities in amniotic fluid volume or fetal growth may indicate potential fetal compromise 2, 6. The results of biophysical profile scoring and Doppler ultrasonography are also used to assess fetal wellbeing and identify potential complications 5, 4.