Five Top Tips for Measuring Amniotic Fluid
Sally Holloway, Rachel Wilkins, Ellen Dyer, Research Sonographers working on the Pregnancy Outcome Prediction Study 2, and employed by the University of Cambridge at the Rosie Hospital, Cambridge, share their 5 top tips for measuring amniotic fluid.
- When measuring the amniotic fluid, the patient should be supine or semi recumbent on the couch with the ultrasound probe held perpendicular to the floor. The gain and TGC should be set so no artefact can be seen within the fluid, especially along the anterior and posterior walls. This prevents under-measuring of fluid.
- The chosen pockets of amniotic fluid should be at least 1cm wide and free from fetal parts and umbilical cord. Use colour Doppler to check no cord is present.
- Be aware of your department guidelines. Does your department use Amniotic Fluid Index (AFI) or Deepest Vertical Pool (DVP)? It is important to ensure that all staff are using the same method and normal ranges, especially when new staff and locums join. Always take at least two measurements of the amniotic fluid as the amount can go up or down depending on fetal activity.
- It is good practice to save images of the amniotic fluid measurement as well as documenting the measurement in the patients’ reports. Fluid should be assessed and measured at every 3rd trimester scan. If there is reduced amniotic fluid (oligohydramnios) or increased (polyhydramnios), check and document whether you can visualise the fetal urinary bladder and stomach.
- When there is no history of ruptured membranes it is important to look for any structural cause to explain why the amniotic fluid is abnormal. This includes absent kidneys, absent stomach, double bubble sign or cleft lip.
Co-authored by Sally Holloway, Rachel Wilkins, Ellen Dyer. All are research sonographers working on the Pregnancy Outcome Prediction Study 2, and employed by the University of Cambridge at the Rosie Hospital, Cambridge.