AFI = Sum of deepest vertical pocket in 4 quadrants (cm)
Normal: 5–25 cm | Oligo: <5 cm | Poly: >25 cm
Amniotic Fluid Index (AFI) Calculator 2025: Detect Oligo & Polyhydramnios
Amniotic fluid protects baby. Our calculator uses **AFI** and **gestational age** to flag **low (oligohydramnios)** or **high (polyhydramnios)** levels.
Normal AFI by Gestational Age
| Weeks | 5th %ile | 50th %ile | 95th %ile |
|---|---|---|---|
| 16 | 7.1 | 12.1 | 18.5 |
| 20 | 8.0 | 13.9 | 21.9 |
| 24 | 9.0 | 14.7 | 22.3 |
| 28 | 9.5 | 14.6 | 21.8 |
| 32 | 9.0 | 14.4 | 21.2 |
| 36 | 7.9 | 13.8 | 20.7 |
| 40 | 5.8 | 11.0 | 19.3 |
AFI Categories
- Normal: 5–25 cm
- Oligohydramnios: <5 cm (or <2 cm deepest pocket)
- Polyhydramnios: >25 cm (or >8 cm deepest pocket)
Causes of Low AFI
- Ruptured membranes (PROM)
- Fetal kidney issues
- Post-term pregnancy
- Maternal dehydration
Causes of High AFI
- Gestational diabetes
- Fetal swallowing defect
- Twins (TTTS)
- Idiopathic
Risks
- Low: Cord compression, growth restriction, preterm birth
- High: Preterm labor, placental abruption, C-section
Management
- Low: Hydration, amnioinfusion, early delivery
- High: Indomethacin, serial amnioreduction
Monitoring
- Weekly NST + BPP if abnormal
- Track with Fetal Growth
FAQs
Can I increase AFI? Drink 2–3L water/day; rest.
AFI vs SDP? SDP = single deepest pocket. AFI more accurate.
Twins AFI? Measured per sac.
Conclusion
Use our **2025 AFI Calculator** with ultrasound results. **Report abnormal AFI to OB immediately**.
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