Table 2.
Birth size measurements, z‐scores and percent below established cut‐offs, relative to 2006 WHO child growth standards and acceptable size‐for‐gestational age distributions
| All | Gestational age (weeks) † | Sex | |||||
|---|---|---|---|---|---|---|---|
| n = 16 290 | ≥37 | 34 to <37 | 32 to <34 | <32 | Boys | Girls | |
| n = 12 042 | n = 2419 | n = 600 | n = 374 | n = 8296 | n = 7994 | ||
| Birth size, mean (SD) | |||||||
| Weight (g) | 2 433 (425) | 2 498 (392) | 2240 (411) | 2094 (493) | 2055 (553) | 2473 (437) | 2392* (408) |
| Length (cm) | 46.4 (2.4) | 46.8 (2.2) | 45.3 (2.5) | 44.4 (3.0) | 44.2 (3.3) | 46.7 (2.5) | 46.1* (2.3) |
| Head circumference (cm) | 32.4 (1.6) | 32.6 (1.5) | 31.6 (1.6) | 30.9 (2.1) | 30.9 (2.5) | 32.6 (1.7) | 32.1* (1.6) |
| Chest circumference (cm) | 30.4 (2.1) | 30.7 (1.9) | 29.4 (2.1) | 28.7 (2.6) | 28.4 (3.1) | 30.5 (2.1) | 30.3* (2.1) |
| Mid‐upper arm circumference (cm) | 9.3 (0.9) | 9.4 (0.8) | 9.0 (0.8) | 8.7 (1.0) | 8.7 (1.1) | 9.3 (0.9) | 9.3 (0.9) |
| Ponderal index, 100 × g cm–3 | 2.42 (0.30) | 2.43 (0.30) | 2.40 (0.30) | 2.35 (0.27) | 2.35 (0.34) | 2.42 (0.31) | 2.43 (0.29) |
| Birth size relative to WHO standard, mean (SD) | |||||||
| WAZ | −1.99 (1.07) | −1.82 (0.97) | −2.48 (1.07) | −2.87 (1.28) | −2.99 (1.46) | −1.99 (1.09) | −1.99 (1.06) |
| LAZ | −1.72 (1.29) | −1.52 (1.15) | −2.32 (1.32) | −2.78 (1.60) | −2.90 (1.78) | −1.75 (1.31) | −1.68* (1.26) |
| HCZ | −1.54 (1.32) | −1.33 (1.17) | −2.14 (1.33) | −2.70 (1.72) | −2.71 (2.04) | −1.50 (1.32) | −1.58* (1.32) |
| Low birthweight ¶ | 9 000 (55.2) | 6 042 (50.2) | 1774 (73.3) | 456 (76.0) | 290 (77.5) | 4224 (50.9) | 4776* (59.7) |
| ≤2 WAZ ¶ | 7 593 (46.6) | 4 924 (40.9) | 1604 (66.3) | 432 (72.0) | 266 (71.1) | 3829 (46.0) | 3773 (46.6) |
| ≤2 LAZ ¶ | 5 892 (37.0) | 3648 (30.9) | 1380 (58.4) | 372 (64.1) | 220 (62.5) | 3115 (38.5) | 2777* (35.5) |
| ≤2 HCZ ¶ | 5 431 (33.6) | 3 296 (27.6) | 1298 (54.1) | 363 (61.0) | 221 (60.4) | 2581 (31.4) | 2850* (35.9) |
| Low MUAC §§ ¶ | 5 065 (31.3) | 3 176 (26.5) | 1115 (46.5) | 331 (55.7) | 209 (58.1) | 2545 (30.9) | 2520 (31.7) |
| Low PI ¶¶ | 2 712 (18.4) | 2 318 (20.5) | 335 (13.8) | 43 (7.2) | 16 (4.3) | 1388 (18.4) | 1324 (18.5) |
| Gestational age at birth n (%) | |||||||
| SGA for weight n (%) | n = 15 435 | n = 12 042 | n = 2419 | n = 600 | n = 374 | n = 7881 | n = 7554 |
| Alexander** | 10 944 (70.9) | 9 647 (80.1) | 1169 (48.3) | 112 (18.7) | 16 (4.3) | 5524 (70.1) | 5420* (71.7) |
| Oken †† | 11 444 (72.2) | 9 892 (82.1) | 1146 (47.4) | 97 (16.2) | 9 (2.4) | 5623 (71.3) | 5521* (73.1) |
| Olsen ‡‡ | 8 533 (59.8) | 7 825 (72.0) | 625 (25.8) | 71 (11.8) | 12 (3.2) | 4290 (58.5) | 4243* (61.2) |
| Oken †† | 7 455 (48.3) | 6 986 (58.0) | 443 (18.3) | 26 (4.3) | 0 (0.0) | 3681 (46.7) | 3774* (50.0) |
| Olsen ‡‡ | 5 110 (35.8) | 4 847 (44.6) | 229 (9.5) | 32 (5.3) | 2 (0.5) | 2550 (34.8) | 2560* (36.9) |
| SGA with low PI n (%) (n = 15 435) ¶¶ | 2 543 (24.5) | 2 244 (24.8) | 268 (22.9) | 25 (22.3) | 6 (37.5) | 1302 (24.8) | 1241 (24.3) |
| SGA for length n (%) | 6423 (46.1) | 5916 (55.6) | 456 (19.3) | 47 (8.1) | 4 (1.1) | 3246 (45.5) | 3177 (46.8) |
| SGA for head circumference n (%) | 4361 (30.8) | 3862 (35.8) | 426 (17.8) | 59 (9.9) | 14 (3.8) | 2112 (29.1) | 2249* (32.3) |
SGA, small‐for‐gestational age; WAZ, weight‐for‐age z‐score; LAZ, length‐for‐age z‐score; HCZ, head circumference‐for‐age z‐score; PI, ponderal index; MUAC, mid‐upper arm circumference. *Indicates girls differ from boys at P < 0.05. †Missing data: gestational age and size for gestational age, n = 855; length and LAZ, n = 374; head circumference and HCZ, n = 135; arm circumference, n = 107; chest circumference, n = 273; Ponderal index, n = 374. ¶Percentages reflect proportion of those within the same gestational age category at birth and are based on number with available data. **Based on Alexander et al. (1996). ††Based on Oken et al. (2003). ‡‡Based on Olsen et al. (2010). §§Low MUAC defined as MUAC < 9 cm based on Goto (2011). ¶¶Low PI was defined as <10th percentile of reference chart of PI for each gestational‐age category based on Lubchenco et al. (1966); PI missing for n = 563 infants with gestational age >42 weeks and n = 521 for infant without gestational‐age data.