Lost ≤ −1 kg/m2 from previous pregnancy | Weight stable (> –1 to <1 kg/m2) | Gained 1–3 kg/m2 from previous pregnancy | Gained ≥3 kg/m2 from previous pregnancy | P value* | |
N | 2548 | 5785 | 4446 | 3161 | |
Maternal age, years (mean±SD) | 28.7±5.4 | 29.8±5.3 | 29.2±5.4 | 27.3±5.5 | <0.001 |
Timing of first booking appointment, weeks (mean±SD) | 10.8±2.3 | 11.0±2.3 | 11.1±2.4 | 11.0±2.6 | <0.001 |
Maternal BMI at booking, kg/m2 (mean±SD) | 24.1±5.1 | 23.8±4.4 | 25.9±4.7 | 30.8±5.9 | <0.001 |
Maternal BMI at booking in first pregnancy (%, 95% CI) | |||||
Underweight (<18.5) | 0.8 (0.5 to 1.2) | 4.3 (3.8 to 4.8) | 5.3 (4.7 to 6.0) | 3.7 (3.1 to 4.4) | <0.001 |
Normal weight (18.5 to 24.9) | 47.6 (45.6 to 49.5) | 67.4 (66.2 to 68.6) | 62.5 (61.0 to 63.9) | 49.0 (47.2 to 50.7) | |
Overweight (25.0 to 29.9) | 30.1 (28.3 to 31.9) | 19.4 (18.4 to 20.5) | 22.0 (20.8 to 23.3) | 29.5 (28.0 to 31.2) | |
Obese (≥30.0) | 21.5 (19.9 to 23.2) | 8.9 (8.2 to 9.7) | 10.2 (9.3 to 11.1) | 17.8 (16.5 to 19.2) | |
Maternal BMI at booking in second pregnancy (%, 95% CI) | |||||
Underweight (<18.5) | 6.9 (5.9 to 7.9) | 4.3 (3.8 to 4.8) | 0.6 (0.4 to 0.9) | 0.0 (0.0 to 0.2) | <0.001 |
Normal weight (18.5 to 24.9) | 61.1 (59.2 to 63.0) | 66.8 (65.6 to 68.1) | 50.7 (49.2 to 52.1) | 14.9 (13.7 to 16.2) | |
Overweight (25.0 to 29.9) | 20.1 (18.6 to 21.7) | 19.7 (18.7 to 20.7) | 32.6 (31.2 to 34.0) | 36.7 (35.0 to 38.4) | |
Obese (≥30.0) | 11.9 (10.7 to 13.3) | 9.2 (8.5 to 10.0) | 16.1 (15.0 to 17.2) | 48.3 (46.6 to 50.1) | |
Maternal smoking status at booking (%, 95% CI) | |||||
Never smoked/quit | 57.2 (55.3 to 59.2) | 63.0 (61.8 to 64.3) | 60.5 (59.0 to 62.0) | 50.7 (48.9 to 52.4) | <0.001 |
Stopped >1 year before conceiving | 16.1 (14.6 to 17.5) | 17.2 (16.3 to 18.2) | 17.7 (16.5 to 18.8) | 14.9 (13.7 to 16.2) | |
Stopped <1 year prior to conceiving | 4.0 (3.3 to 4.8) | 2.8 (2.4 to 3.2) | 3.5 (3.0 to 4.1) | 4.9 (4.2 to 5.7) | |
Stopped when pregnancy confirmed | 6.8 (5.8 to 7.8) | 5.9 (5.3 to 6.6) | 6.9 (6.2 to 7.7) | 10.3 (9.3 to 11.4) | |
Continued smoking | 15.9 (14.5 to 17.4) | 11.0 (10.2 to 11.8) | 11.4 (10.5 to 12.4) | 19.1 (17.8 to 20.6) | |
Maternal education (%, 95% CI) | |||||
Secondary (GCSE) or under | 30.7 (28.9 to 32.5) | 24.0 (22.9 to 25.2) | 29.4 (28.1 to 30.8) | 36.3 (34.6 to 38.0) | <0.001 |
College (A levels) | 40.4 (38.5 to 42.3) | 38.8 (37.6 to 40.1) | 39.5 (38.1 to 41.0) | 45.8 (44.0 to 47.5) | |
University degree or above | 28.9 (27.2 to 30.7) | 37.1 (35.9 to 38.4) | 31.1 (29.7 to 32.5) | 17.9 (16.6 to 19.3) | |
Maternal employment (%, 95% CI) | |||||
Employed | 66.2 (64.3 to 68.0) | 71.7 (70.5 to 72.9) | 67.2 (65.8 to 68.5) | 56.5 (54.8 to 58.2) | <0.001 |
Unemployed | 31.8 (30.0 to 33.7) | 26.9 (25.8 to 28.1) | 31.1 (29.7 to 32.5) | 41.6 (39.8 to 43.3) | |
In education | 0.9 (0.6 to 1.4) | 0.8 (0.6 to 1.1) | 1.1 (0.8 to 1.4) | 1.3 (0.9 to 1.8) | |
Not specified | 1.0 (0.7 to 1.5) | 0.6 (0.4 to 0.8) | 0.7 (0.5 to 1.0) | 0.6 (0.4 to 1.0) | |
Ethnicity (%, 95% CI) | |||||
White | 89.9 (88.7 to 91.1) | 88.0 (87.1 to 88.8) | 85.1 (84.0 to 86.1) | 84.8 (83.5 to 86.1) | <0.001 |
Mixed | 0.8 (0.5 to 1.3) | 0.9 (0.7 to 1.2) | 1.4 (1.1 to 1.8) | 1.6 (1.1 to 2.0) | |
Asian | 4.8 (4.0 to 5.7) | 5.6 (5.0 to 6.0) | 7.2 (6.5 to 8.0) | 7.7 (6.8 to 8.7) | |
Black/African/Caribbean | 0.6 (0.4 to 1.0) | 1.0 (0.8 to 1.3) | 1.6 (1.3 to 2.1) | 2.4 (1.9 to 3.0) | |
Other | 0.7 (0.4 to 1.1) | 1.0 (0.8 to 1.3) | 1.0 (0.8 to 1.4) | 1.3 (0.9 to 1.7) | |
Not specified | 3.1 (2.5 to 3.9) | 3.5 (3.0 to 4.0) | 3.6 (3.1 to 4.2) | 2.2 (1.8 to 2.8) | |
Interpregnancy interval (median, IQR) | 21.7 (14.4 to 32.7) | 21.6 (14.1 to 32.0) | 23.7 (14.4 to 35.6) | 27.7 (16.0 to 45.6) | <0.001 |
Interpregnancy interval (%, 95% CI) | |||||
0–11 months | 17.4 (15.9 to 18.9) | 17.6 (16.6 to 18.6) | 18.1 (17.0 to 19.3) | 16.6 (15.4 to 17.9) | <0.001 |
12–23 months | 39.8 (37.8 to 41.7) | 39.9 (38.6 to 41.1) | 33.1 (31.7 to 34.5) | 26.3 (24.8 to 27.9) | |
24–35 months | 22.6 (21.0 to 24.2) | 23.6 (22.5 to 24.7) | 24.4 (23.2 to 25.7) | 20.5 (19.1 to 21.9) | |
36 months or more | 20.3 (18.7 to 21.9) | 18.9 (17.9 to 20.0) | 24.3 (23.1 to 25.6) | 36.5 (34.9 to 38.2) | |
Birth weight, g (mean±SD) | 3463±563 | 3467±523 | 3507±536 | 3531±558 | |
Previous size at birth (first pregnancy) | |||||
Small-for-gestational age | 13.1 (11.8 to 14.4) | 12.6 (11.8 to 13.5) | 11.7 (10.8 to 12.7) | 12.4 (11.3 to 13.6) | 0.11 |
Appropriate-for-gestational age | 79.6 (77.9 to 81.1) | 81.1 (80.0 to 82.1) | 81.2 (80.1 to 82.4) | 79.9 (78.4 to 81.3) | |
Large-for-gestational age | 7.4 (6.4 to 8.5) | 6.3 (5.7 to 7.0) | 7.1 (6.3 to 7.8) | 7.7 (6.8 to 8.7) | |
Size at birth (second pregnancy) | |||||
Small-for-gestational age | 8.7 (7.6 to 9.8) | 7.0 (6.4 to 7.7) | 6.2 (5.5 to 6.9) | 6.7 (5.9 to 7.6) | <0.001 |
Appropriate-for-gestational age | 79.0 (77.3 to 80.5) | 81.1 (80.0 to 82.1) | 80.3 (79.1 to 81.5) | 77.4 (75.9 to 78.9) | |
Large-for-gestational age | 12.4 (11.1 to 13.7) | 11.9 (11.1 to 12.8) | 13.5 (12.5 to 14.5) | 15.9 (14.6 to 17.2) |
↵*P values calculated using ANOVA for continuous and χ2 test for categorical variables.