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Ultrasound Anomaly: Amniotic Fluid Index (AFI) vs. Deepest Vertical Pocket (DVP)

  • Writer: Mayta
    Mayta
  • Dec 28, 2024
  • 2 min read

Introduction

The assessment of amniotic fluid levels during pregnancy is crucial for fetal well-being. Two main methods are employed: Amniotic Fluid Index (AFI) and Deepest Vertical Pocket (DVP). While both approaches aim to estimate amniotic fluid levels, they differ in methodology, sensitivity, specificity, and clinical implications.

 

Amniotic Fluid Index (AFI)

Definition:

  • The AFI is the sum of the maximum vertical depths of amniotic fluid in each of the four uterine quadrants. The quadrants are created by dividing the uterus using the linea nigra (longitudinal) and a transverse line through the umbilicus.

Normal Range:

  • 5–25 cm:

    • Low normal: 5–8 cm.

    • Normal: 8–25 cm.

  • <5 cm: Indicates oligohydramnios (insufficient amniotic fluid).

  • >25 cm: Indicates polyhydramnios (excessive amniotic fluid).

Utility:

  • Widely utilized in fetal biophysical profiles (BPP).

  • Peaks at 32–34 weeks of gestation, decreasing as pregnancy progresses.

Advantages:

  • Sensitivity: Effective in detecting fluid volume changes, especially decreases.

  • Provides a comprehensive overview of overall amniotic fluid volume.

Disadvantages:

  • Over-diagnoses oligohydramnios, which can lead to unnecessary interventions like induction or cesarean delivery.


 

Deepest Vertical Pocket (DVP)

Definition:

  • Measures the depth of the single largest vertical pocket of amniotic fluid free from umbilical cord and fetal parts.

Normal Range:

  • 2–8 cm:

    • <2 cm: Oligohydramnios.

    • >8 cm: Polyhydramnios.

Utility:

  • Often used as an alternative or adjunct to AFI in amniotic fluid assessment.

Advantages:

  • Specificity: Reduces over-diagnosis of oligohydramnios compared to AFI.

  • Easier and faster to perform in clinical practice.

Disadvantages:

  • May miss small or localized changes in amniotic fluid distribution.


 

Comparison Between AFI and DVP

Aspect

AFI

DVP

Method

Summation of fluid pockets in four quadrants.

Single deepest pocket measurement.

Normal Range

5–25 cm

2–8 cm

Sensitivity

Higher sensitivity for oligohydramnios.

Lower sensitivity.

Specificity

Lower specificity; prone to overdiagnosis.

Higher specificity.

Overdiagnosis

More frequent.

Less frequent.

Use in BPP

Frequently included.

Sometimes preferred for simplicity.

Outcome Prediction

Controversial; study results vary.

Controversial; study results vary.

Clinical Implications

Oligohydramnios:

  • AFI: Likely to detect more cases due to higher sensitivity, potentially leading to over-treatment.

  • DVP: Provides a conservative approach, reducing unnecessary interventions.

Polyhydramnios:

  • Both methods identify excess amniotic fluid well. However, DVP may miss localized pockets of excess fluid due to its focused measurement.


 

Conclusion

The choice between AFI and DVP depends on clinical context, the clinician’s expertise, and equipment availability. AFI offers a broader picture of fluid volume but may overestimate abnormalities, whereas DVP provides simplicity and specificity, reducing false positives for oligohydramnios. Integrating both methods when necessary can enhance diagnostic accuracy and guide appropriate management.

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Message for International Readers
Understanding My Medical Context in Thailand

By Uniqcret, M.D.
 

Dear readers,
 

My name is Uniqcret, which is my pen name used in all my medical writings. I am a Doctor of Medicine trained and currently practicing in Thailand, a developing country in Southeast Asia.
 

The medical training environment in Thailand is vastly different from that of Western countries. Our education system heavily emphasizes rote memorization—those who excel are often seen as "walking encyclopedias." Unfortunately, those who question, critically analyze, or solve problems efficiently may sometimes be overlooked, despite having exceptional clinical thinking skills.
 

One key difference is in patient access. In Thailand, patients can walk directly into tertiary care centers without going through a referral system or primary care gatekeeping. This creates an intense clinical workload for doctors and trainees alike. From the age of 20, I was already seeing real patients, performing procedures, and assisting in operations—not in simulations, but in live clinical situations. Long work hours, sometimes exceeding 48 hours without sleep, are considered normal for young doctors here.
 

Many of the insights I share are based on first-hand experiences, feedback from attending physicians, and real clinical practice. In our culture, teaching often involves intense feedback—what we call "โดนซอย" (being sliced). While this may seem harsh, it pushes us to grow stronger, think faster, and become more capable under pressure. You could say our motto is “no pain, no gain.”
 

Please be aware that while my articles may contain clinically accurate insights, they are not always suitable as direct references for academic papers, as some content is generated through AI support based on my knowledge and clinical exposure. If you wish to use the content for academic or clinical reference, I strongly recommend cross-verifying it with high-quality sources or databases. You may even copy sections of my articles into AI tools or search engines to find original sources for further reading.
 

I believe that my knowledge—built from real clinical experience in a high-intensity, under-resourced healthcare system—can offer valuable perspectives that are hard to find in textbooks. Whether you're a student, clinician, or educator, I hope my content adds insight and value to your journey.
 

With respect and solidarity,

Uniqcret, M.D.

Physician | Educator | Writer
Thailand

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