Fetal Growth Percentile Calculator | INTERGROWTH-21st Standards
Monitoring fetal growth is a critical part of prenatal care. The INTERGROWTH-21st study established international standards for fetal growth based on data from healthy pregnancies worldwide. This calculator helps you assess your baby's growth percentile based on gestational age and estimated fetal weight.
Understanding fetal growth percentiles can help identify potential concerns early. A baby below the 10th percentile may be small for gestational age (SGA), while a baby above the 90th percentile may be large for gestational age (LGA). Your healthcare provider will interpret these results in context of your individual pregnancy.
All calculations and data on this website are for informational reference only. This tool does not provide medical advice, diagnosis, or treatment. For health-related concerns, please consult a qualified healthcare professional.
Fetal Growth Assessment
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Calculation Examples
Example 1 �?Normal Growth (50th Percentile)
Gestational Age = 32 weeks
Estimated Fetal Weight = 1700 g
Mean Weight at 32 weeks = 1700 g
Z-Score = 0
Percentile = 50th
Classification = Appropriate for Gestational Age
Estimated Fetal Weight = 1700 g
Mean Weight at 32 weeks = 1700 g
Z-Score = 0
Percentile = 50th
Classification = Appropriate for Gestational Age
Example 2 �?Small for Gestational Age
Gestational Age = 34 weeks
Estimated Fetal Weight = 1500 g
Mean Weight at 34 weeks = 2000 g
Z-Score = -2.0
Percentile = 2.3rd
Classification = Small for Gestational Age (SGA)
Estimated Fetal Weight = 1500 g
Mean Weight at 34 weeks = 2000 g
Z-Score = -2.0
Percentile = 2.3rd
Classification = Small for Gestational Age (SGA)
Example 3 �?Large for Gestational Age
Gestational Age = 38 weeks
Estimated Fetal Weight = 4200 g
Mean Weight at 38 weeks = 3100 g
Z-Score = +2.5
Percentile = 99th
Classification = Large for Gestational Age (LGA)
Estimated Fetal Weight = 4200 g
Mean Weight at 38 weeks = 3100 g
Z-Score = +2.5
Percentile = 99th
Classification = Large for Gestational Age (LGA)
Data Source and References
- [1] INTERGROWTH-21st Project Group (2014). International standards for fetal growth. The Lancet, 384(9946):869-877.
- [2] WHO (2006). WHO Child Growth Standards. WHO Press.
- [3] ACOG (2023). Clinical Guidelines for Fetal Growth Surveillance. Obstetrics & Gynecology.
- [4] Villar J et al. (2014). International standards for newborn weight, length, and head circumference by gestational age and sex. The Lancet, 384(9946):878-888.
INTERGROWTH-21st Fetal Growth Standards
The INTERGROWTH-21st study established the following key findings for fetal growth:
| Gestational Age | Mean Weight (g) | 5th Percentile (g) | 50th Percentile (g) | 95th Percentile (g) |
|---|---|---|---|---|
| 20 weeks | 330 | 240 | 330 | 440 |
| 24 weeks | 650 | 480 | 650 | 870 |
| 28 weeks | 1100 | 820 | 1100 | 1470 |
| 32 weeks | 1700 | 1270 | 1700 | 2260 |
| 36 weeks | 2500 | 1870 | 2500 | 3320 |
| 40 weeks | 3500 | 2620 | 3500 | 4650 |
Fetal Growth Classification
| Percentile Range | Classification | Abbreviation | Clinical Significance |
|---|---|---|---|
| < 3rd | Severely Small | Severe SGA | High risk of adverse outcomes |
| 3rd - 10th | Small for Gestational Age | SGA | Requires closer monitoring |
| 10th - 90th | Appropriate for Gestational Age | AGA | Normal growth |
| 90th - 97th | Large for Gestational Age | LGA | Increased delivery complications |
| > 97th | Severely Large | Severe LGA | High risk of shoulder dystocia |
Factors Affecting Fetal Growth
Several factors can influence fetal growth patterns:
- Maternal Factors: Maternal weight, height, nutritional status, smoking, chronic conditions
- Placental Factors: Placental function, umbilical cord blood flow
- Genetic Factors: Parental size, fetal gender
- Environmental Factors: Exposure to toxins, infections
- Multiple Gestation: Twins, triplets typically have lower individual birth weights
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Frequently Asked Questions
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Fetal growth percentile compares your baby's estimated weight to the average weight of babies at the same gestational age. A percentile of 50 means the baby's weight is average. Percentiles below 10 or above 90 may indicate growth concerns that should be discussed with a healthcare provider.
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INTERGROWTH-21st is an international study that established new fetal growth standards based on data from healthy pregnancies across multiple ethnic groups. It provides more accurate growth percentiles than previous standards, especially for early and late gestations.
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Fetal weight is estimated through ultrasound measurements including: biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). These measurements are entered into mathematical formulas to calculate an estimated fetal weight (EFW).
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If fetal growth is below the 10th percentile (small for gestational age), your healthcare provider will monitor the pregnancy more closely. They may recommend additional ultrasounds, non-stress tests, or delivery planning if growth restriction is confirmed.
All calculations and data on this website are for informational reference only. This tool does not provide medical advice, diagnosis, or treatment. For health-related concerns, please consult a qualified healthcare professional.