Fetal BPD / AC / FL Reference Table
Median and reference-range values of BPD, AC, and FL for every week from 14 to 42, based on the Expert Consensus on Fetal Biometric Ultrasound Reference Values (2024).
| Weeks | BPD (mm) | AC (mm) | FL (mm) | Daily details |
|---|---|---|---|---|
| Week 14 | 26.4（22.8–30.6） | 78.4（68.8–89.4） | 12.2（9.8–15.3） | View week 14 |
| Week 15 | 30.1（26.1–34.7） | 90.4（79.7–102.5） | 15.7（12.7–19.3） | View week 15 |
| Week 16 | 33.6（29.3–38.5） | 102.5（90.8–115.6） | 19.1（15.7–23.3） | View week 16 |
| Week 17 | 36.9（32.4–42.1） | 114.5（101.8–128.6） | 22.4（18.7–26.9） | View week 17 |
| Week 18 | 40（35.3–45.4） | 126.3（112.9–141.4） | 25.4（21.4–30.1） | View week 18 |
| Week 19 | 43.1（38.1–48.6） | 138（123.8–153.9） | 28.2（24.1–33.1） | View week 19 |
| Week 20 | 46.1（41–51.8） | 149.6（134.6–166.3） | 31（26.7–36） | View week 20 |
| Week 21 | 49.2（44–55.1） | 161.1（145.3–178.6） | 33.8（29.4–38.8） | View week 21 |
| Week 22 | 52.3（47–58.4） | 172.4（155.9–190.6） | 36.5（32.1–41.5） | View week 22 |
| Week 23 | 55.5（49.9–61.6） | 183.4（166.2–202.5） | 39.1（34.7–44.2） | View week 23 |
| Week 24 | 58.6（52.9–64.9） | 194.3（176.3–214.1） | 41.7（37.2–46.8） | View week 24 |
| Week 25 | 61.7（55.9–68.1） | 204.9（186.1–225.6） | 44.2（39.6–49.4） | View week 25 |
| Week 26 | 64.7（58.8–71.3） | 215.4（195.7–237） | 46.6（42–51.8） | View week 26 |
| Week 27 | 67.7（61.6–74.3） | 225.8（205.2–248.4） | 49（44.2–54.2） | View week 27 |
| Week 28 | 70.6（64.4–77.3） | 236.1（214.5–259.9） | 51.2（46.3–56.6） | View week 28 |
| Week 29 | 73.3（67–80.2） | 246.7（223.9–271.7） | 53.4（48.4–58.9） | View week 29 |
| Week 30 | 76（69.5–83） | 257.3（233.4–283.7） | 55.5（50.4–61.1） | View week 30 |
| Week 31 | 78.5（71.9–85.6） | 268（242.8–295.9） | 57.5（52.3–63.4） | View week 31 |
| Week 32 | 80.8（74.1–88.1） | 278.7（252–308.2） | 59.5（54.1–65.5） | View week 32 |
| Week 33 | 83（76.2–90.4） | 289.1（260.9–320.4） | 61.4（55.8–67.6） | View week 33 |
| Week 34 | 85（78–92.6） | 299.3（269.5–332.3） | 63.2（57.5–69.6） | View week 34 |
| Week 35 | 86.8（79.7–94.5） | 309（277.6–343.9） | 65（59–71.5） | View week 35 |
| Week 36 | 88.5（81.2–96.3） | 318.3（285.2–355.1） | 66.7（60.6–73.4） | View week 36 |
| Week 37 | 89.9（82.6–97.9） | 327.2（292.4–366） | 68.3（62–75.1） | View week 37 |
| Week 38 | 91.1（83.7–99.2） | 335.9（299.4–376.8） | 69.7（63.3–76.8） | View week 38 |
| Week 39 | 92.1（84.6–100.3） | 344.5（306.2–387.7） | 71.1（64.5–78.3） | View week 39 |
| Week 40 | 93（85.3–101.3） | 353.3（312.9–398.9） | 72.4（65.6–79.9） | View week 40 |
Note: values show the 50th-percentile median with the 3rd–97th percentile range in brackets. Individual variation is common; a single measurement slightly outside the range is not necessarily abnormal. Always interpret with the full ultrasound report and a doctor's assessment.
About ultrasound reference values
- What is BPD (biparietal diameter)?
- The widest measurement across the fetal head, a key indicator for estimating gestational age and head development.
- What do AC and FL represent?
- AC (abdominal circumference) reflects the development of the abdominal organs and fat, while FL (femur length) reflects the lower-limb long bones. Together they help assess fetal growth.
- My values fall outside the range — is that normal?
- The reference ranges are population-based statistical intervals, not a hard pass/fail boundary. Being slightly outside may result from measurement angle, fetal position, or individual variation. A doctor should assess it together with other indicators; do not draw conclusions from a single measurement.
Data note: BPD, AC, and FL reference values follow the median and 3rd–97th percentile ranges of the Expert Consensus (2024) (weeks 14–40 in the consensus; weeks 41–42 are not listed because the consensus provides no ranges). This table is for pregnancy education and general reference only and does not replace professional ultrasound diagnosis.