Temporal trends in mean birth weight (g) in all births 1986–2012 (ONS data) and all, term and preterm births 2006–2012 (NN4B data)
| Unadjusted yearly birth weight change (g) (95% CI) | Adjusted* yearly birth weight change (g) (95% CI) | Unadjusted birth weight change (g) (95% CI) for whole study period† | Adjusted birth weight change (g) (95% CI) for whole study period† | |
| ONS births 1986–2012 | ||||
| Female births | 1.4 (1.3 to 1.4) | 1.6 (1.5 to 1.6) | 37.0 (35.9 to 38.3) | 42.9 (41.6 to 44.0) |
| Male births | 1.4 (1.4 to 1.5) | 1.6 (1.6 to 1.7) | 38.1 (36.7 to 39.2) | 44.0 (42.7 to 45.4) |
| NN4B 2006–2012 | ||||
| Female | ||||
| All births | 3.4 (3.0 to 3.7) | 3.9 (3.6 to 4.3) | 23.7 (21.2 to 26.1) | 27.6 (25.1 to 30.1) |
| Term births | 2.3 (1.9 to 2.6) | 2.7 (2.4 to 3.1) | 15.8 (13.6 to 18.1) | 19.2 (16.9 to 21.4) |
| Preterm births | 4.3 (2.3 to 6.2) | 4.3 (2.4 to 6.3) | 29.8 (16.3 to 43.3) | 30.2 (16.5 to 44.1) |
| Male | ||||
| All births | 3.8 (3.4 to 4.1) | 4.4 (4.0 to 4.8) | 26.5 (23.9 to 29.0) | 30.9 (28.3 to 33.5) |
| Term births | 2.5 (2.2 to 2.8) | 3.0 (2.7 to 3.3) | 17.6 (15.4 to 19.9) | 21 (18.8 to 23.3) |
| Preterm births | 4.4 (2.3 to 6.2) | 4.3 (2.5 to 6.1) | 30.6 (16.0 to 43.1) | 30.2 (17.4 to 43.0) |
*Adjusted for maternal age, marital status, area-level deprivation, area-level ethnicity (ONS) and individual ethnicity (NN4B).
†Birth weight change pooled for whole study period: ONS (1986–2012), NN4B (2006–2012).
NN4B, NHS Numbers for Babies; ONS, Office for National Statistics.