This table shows the percentiles of birthweights in grams by weeks of the pregnancy and gestational age.
Percentiles of Birth Weight (grams) for gestational Age: US 1991 Single Births
Alexander et al Ob-Gyn 1996
| Weeks | 10th%tile | Average | 90th%tile |
| 20 | 275 | 412 | 772 |
| 21 | 314 | 433 | 790 |
| 22 | 376 | 496 | 826 |
| 23 | 440 | 582 | 882 |
| 24 | 498 | 674 | 977 |
| 25 | 558 | 779 | 1138 |
| 26 | 625 | 899 | 1362 |
| 27 | 702 | 1035 | 1635 |
| 28 | 798 | 1196 | 1977 |
| 29 | 925 | 1394 | 2361 |
| 30 | 1085 | 1637 | 2710 |
| 31 | 1278 | 1918 | 2986 |
| 32 | 1495 | 2203 | 3200 |
| 33 | 1725 | 2458 | 3370 |
| 34 | 1950 | 2667 | 3502 |
| 35 | 2159 | 2831 | 3596 |
| 36 | 2354 | 2974 | 3668 |
| 37 | 2541 | 3117 | 3755 |
| 38 | 2714 | 3263 | 3867 |
| 39 | 2852 | 3400 | 3980 |
| 40 | 2929 | 3495 | 4060 |
| 41 | 2948 | 3527 | 4094 |
| 42 | 2935 | 3522 | 4098 |
| 43 |
2907 | 3505 | 4096 |
| 44 | 2885 | 3491 | 4096 |