LMP Based Fetal Biometry calculator

Fetal Biometry Calculator — Measurement Panels

The "Enter measurements shown below" area is now organized into three clear panels: Gestational Sac (GS / MSD), CRL (first trimester embryo), and Second/Third trimester biometry. Based on LMP the appropriate panel will be expanded automatically; you can still open other panels if needed.

Last Menstrual Period (LMP)

Gestational sac (GS) / Mean sac diameter (MSD)

Use MSD when embryo/CRL not visible (<6+0 wks). Enter MSD in mm.

MSD (mm)

Approx 10th–95th percentile MSD by week

Week	10th (mm)	Median (mm)	95th (mm)
4	4	5	6
5	9	10	12
6	13	15	18
7	17	20	23
8	21	25	29
9	26	30	35

Crown-Rump Length (CRL)

Preferred dating parameter from 6+0 to 13+6 weeks. Enter CRL in mm.

CRL (mm)

Approx 10th–95th percentile CRL by week

Week	10th (mm)	Median (mm)	95th (mm)
6	4	6	8
7	11	13	16
8	20	24	28
9	28	33	39
10	36	41	47
11	45	51	58
12	55	61	70
13	66	73	84

Second & Third Trimester Biometry

Enter standard measurements used from 14 weeks onwards. Each parameter shows approximate 10th–95th percentile for the current GA when calculated.

Biparietal diameter (BPD) — mm

Head circumference (HC) — mm

Abdominal circumference (AC) — mm

Femur length (FL) — mm

Fetal heart rate (FHR) — bpm

Amniotic fluid index (AFI) — cm

After entering measurements use the "Calculate Biometry & EFW" button to get percentiles (approx 10th–95th), flags, and EFW.

Notes:

• The calculator expands the panel recommended by LMP automatically, but you may open other panels manually.
• Percentile tables shown are approximate. For clinical reporting you can request integration of official centile datasets (INTERGROWTH, WHO, Hadlock).

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Fetal Biometry Calculator — User Manual

This calculator estimates gestational age (GA), expected due date (EDD), and compares fetal biometric parameters against approximate 10th–95th percentile ranges. It is intended for educational and reference use only.

How to Use

1. Enter LMP: Select the patient’s last menstrual period (LMP) date.
2. Automatic Mode Selection:
   • < 6+0 weeks → Gestational sac (GS/MSD) panel expands.
   • 6+0 to 13+6 weeks → CRL panel expands.
   • ≥ 14 weeks → 2nd/3rd trimester biometry panel expands.
3. Enter Measurements:
   • MSD: Enter mean sac diameter in mm (before embryo visible).
   • CRL: Enter crown–rump length in mm (preferred for 6–13+6 weeks).
   • 2nd/3rd Trimester: Enter BPD, HC, AC, FL (mm). Optionally add FHR (bpm) and AFI (cm).
4. Calculate: Click “Calculate Biometry & EFW” to compute percentile ranges, flags, and estimated fetal weight (EFW).
5. Interpretation:
   • Within 10–95th percentile: Normal range.
   • Below 10th percentile: Possible growth restriction (SGA).
   • Above 95th percentile: Possible large for gestational age (LGA).
   • AFI: Normal 5–25 cm. <5 → oligohydramnios; >25 → polyhydramnios.
   • FHR: Normal 110–160 bpm. Outside this → tachycardia or bradycardia.

Additional Features

• Panel Controls: Manual buttons let you expand/collapse GS, CRL, or 2nd/3rd trimester panels at any time.
• Percentiles: Displayed as approximate 10th–95th bands derived from median values. Official centile datasets (e.g., INTERGROWTH, WHO, Hadlock) can be integrated for precise centiles.
• EFW (Hadlock formula): Uses AC + FL (plus BPD/HC if entered). Compared with approximate median weight for GA and flagged if below 10th or above 95th.

Limitations

• Percentiles and medians used here are approximations, not validated charts.
• CRL, MSD, and biometric ranges vary between populations and equipment.
• EFW is an estimate and may vary ±10–15% from actual fetal weight.
• No database storage — results are not saved automatically.

Declaration

This calculator is intended for educational and reference purposes only. It must not be used as the sole basis for clinical diagnosis, treatment, or management. Clinical interpretation should always rely on validated growth charts, institutional guidelines, and professional judgment. The authors/developers accept no liability for misuse or clinical decisions based solely on this tool.