| Head circumference (mm) | |||
| GA (weeks) | 50th centile | 5th centile | 95th centile |
| 12 | 68.1 | 75.1 | 79.2 |
| 13 | 82.2 | 70.8 | 93.6 |
| 14 | 96.0 | 84.2 | 107.8 |
| 15 | 109.7 | 79.5 | 121.9 |
| 16 | 123.1 | 110.6 | 135.7 |
| 17 | 136.4 | 123.4 | 149.3 |
| 18 | 149.3 | 136.0 | 162.7 |
| 19 | 162.0 | 148.3 | 175.7 |
| 20 | 174.5 | 160.4 | 188.6 |
| 21 | 186.6 | 172.1 | 202.1 |
| 22 | 198.5 | 183.6 | 213.3 |
| 23 | 210.0 | 194.8 | 225.3 |
| 24 | 221.2 | 205.6 | 236.9 |
| 25 | 232.1 | 216.1 | 248.1 |
| 26 | 242.6 | 226.2 | 259.0 |
| 27 | 252.7 | 235.9 | 269.5 |
| 28 | 262.5 | 245.3 | 279.6 |
| 29 | 271.8 | 254.3 | 289.4 |
| 30 | 280.7 | 262.8 | 298.7 |
| 31 | 289.2 | 270.9 | 307.6 |
| 32 | 297.3 | 278.6 | 316.0 |
| 33 | 304.9 | 285.8 | 324.0 |
| 34 | 312.0 | 292.6 | 331.5 |
| 35 | 318.7 | 298.8 | 338.5 |
| 36 | 324.8 | 340.6 | 345.0 |
| 37 | 330.4 | 309.8 | 351.0 |
| 38 | 335.5 | 314.5 | 356.5 |
| 39 | 340.0 | 318.7 | 361.4 |
| 40 | 344.0 | 322.3 | 365.8 |
| 41 | 347.4 | 325.3 | 369.6 |
| 42 | 350.3 | 327.7 | 372.8 |