How to calculate fetal weight from B-ultrasound
During pregnancy, one of the issues that expectant mothers are most concerned about is the growth and development of the fetus. Through B-ultrasound examination, doctors can obtain various data of the fetus and estimate the fetal weight. This article will introduce in detail how to calculate fetal weight from single B-ultrasound data, and attach a structured data table to help expectant mothers better understand.
1. Key data on the B-ultrasound sheet
The following key data are usually displayed on the B-ultrasound sheet, which are the basis for calculating fetal weight:
| Data name | Abbreviation | Description |
|---|---|---|
| biparietal diameter | BPD | The maximum distance between the left and right sides of the fetal head |
| Abdominal circumference | AC | The circumference of the fetal abdomen |
| femur length | FL | fetal thigh bone length |
| Head circumference | HC | Circumference of fetal head |
2. Fetal weight calculation formula
Based on the data on the B-ultrasound sheet, doctors usually use the following formula to estimate fetal weight:
| Formula name | Calculation formula | Applicable gestational age |
|---|---|---|
| Hadlock formula | Log10(weight) = 1.326 - 0.00326 × AC × FL + 0.0107 × HC + 0.0438 × AC + 0.158 × FL | whole pregnancy |
| Shepard formula | Log10(weight) = -1.7492 + 0.166 × BPD + 0.046 × AC - 0.002646 × AC × BPD | Middle and late period |
| Simple formula | Body weight (g) = 1.07 × BPD³ + 0.3 × AC² × FL | late pregnancy |
3. How to interpret B-ultrasound single data
The following is an example of B-ultrasound single data and corresponding fetal weight estimation:
| Data name | numerical value | unit |
|---|---|---|
| Biparietal diameter (BPD) | 8.5 | cm |
| Abdominal circumference (AC) | 27.6 | cm |
| Femoral length (FL) | 6.7 | cm |
| Head circumference (HC) | 30.2 | cm |
| Estimated weight | About 2500g | grams |
4. Precautions
1.Data error: There is a certain error in the fetal weight estimated by B-ultrasound, usually the error range is between ±10% and 15%.
2.Doctor's interpretation: The data on the B-ultrasound sheet needs to be interpreted by a professional doctor, and expectant mothers should not over-interpret it on their own.
3.Regular inspection: Fetal growth and development is a dynamic process, and it is recommended to conduct regular B-ultrasound examinations to monitor growth trends.
4.comprehensive assessment: The estimation of fetal weight needs to combine multiple data, and a single data may not accurately reflect the actual situation.
5. Comparison table of fetal weight and gestational age
The following is a reference comparison table of fetal weight and gestational age:
| Gestational age | Average weight (g) | Normal range(g) |
|---|---|---|
| 20 weeks | 300 | 250-350 |
| 24 weeks | 600 | 500-700 |
| 28 weeks | 1100 | 900-1300 |
| 32 weeks | 1800 | 1500-2100 |
| 36 weeks | 2700 | 2400-3000 |
| 40 weeks | 3400 | 3000-3800 |
6. Summary
Calculating fetal weight from single B-ultrasound data is an important means of monitoring fetal growth and development during pregnancy. Expectant mothers should understand the key data on the B-ultrasound sheet, but do not need to pay too much attention to the specific values. They should pay more attention to the doctor's professional interpretation and suggestions. Regular prenatal check-ups, a reasonable diet and appropriate exercise are the keys to ensuring healthy fetal development.
If you have any questions about the data on the B-ultrasound sheet, it is recommended to consult an obstetrician in time to obtain professional answers and guidance.
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