Birth characteristics of a sample of Danish twin pairs, 3–9 years of age
| Zygosity | Number (%) | Birth weight mean (SD) | Birth length mean (SD) | Birth BMI (SD) | Gestational age (SD) | Apgar score | Current age (SD) | Asthma (%) |
| MZ | 1950 (11.8) | 2508 (547) | 47.75 (3.33) | 11.00 (1.30) | 253.03 (17.39) | 9.70 (1.03) | 5.92 (1.99) | 213 (11.8) |
| DZ-ss | 4854 (29.3) | 2580 (582) | 48.10 (3.35) | 11.15 (1.45) | 254.59 (17.84) | 9.73 (0.94) | 5.86 (1.98) | 499 (11.0) |
| DZ-os | 6350 (38.3) | 2567 (594) | 47.99 (3.59) | 11.14 (1.52) | 253.97 (19.31) | 9.68 (1.16) | 5.90 (2.00) | 412 (10.3) |
| All DZ | 11204 (67.7) | 2572 (589) | 48.04 (3.49) | 11.15 (1.49) | 254.24 (18.69) | 9.70 (1.07) | 5.88 (1.99) | 911 (10.7) |
| UZ | 3406 (20.6) | 2418 (671) | 47.01 (4.45) | 10.94 (1.66) | 249.30 (23.85) | 9.48 (1.62) | 6.03 (2.02) | 31 (6.9) |
| Males | 8491 (51) | 2567 (623) | 48.03 (3.82) | 11.13 (1.52) | 252.52 (20.35) | 9.63 (1.25) | 5.92 (1.98) | 698 (12.7) |
| Females | 8069 (49) | 2498 (583) | 47.56 (3.57) | 11.05 (1.49) | 253.67 (19.22) | 9.68 (1.15) | 5.92 (2.01) | 457 (8.7) |
| Total | 16560 (100) | 2534 (605) | 47.80 (3.71) | 11.09 (1.51) | 253.08 (19.81) | 9.65 (1.20) | 5.92 (2.00) | 1155 (10.7) |
Birth weight is given in g, birth length in cm, BMI is in kg/m2, gestational age is in days and current age is in years.
Means and proportions are calculated from available data for the individual variables.
BMI, body mass index; DZ-os, dizygotic opposite sex; DZ-ss, dizygotic same sex; MZ, monozygotic; UZ, unknown zygosity.