Table 1.
Characteristics of mothers and offspring who had information on at least one set of outcome variables (questionnaire‐based, asthma, allergic sensitisation, IgE or lung function) by quintiles of the mother's first pregnancy haemoglobin measurement (total N = 7,270)
| Total N (%) | Quintiles of first haemoglobin % or mean (SD) | P for difference | |||||
|---|---|---|---|---|---|---|---|
| 1st(≤11.8 g/dL) | 2nd (11.9‐12.3 g/dL) | 3rd(12.4‐12.7 g/dL) | 4th(12.8‐13.2 g/dL) | 5th(≥13.3 g/dL) | |||
| Gestation at first haemoglobin (wk) | 7270 | 10.8 (2.9) | 10.3 (2.6) | 10.1 (2.6) | 9.9 (2.5) | 9.6 (2.5) | <.001 |
| Last maternal haemoglobin (g/dL) | 7270 | 11.03 (0.91) | 11.24 (0.82) | 11.40 (0.82) | 11.54 (0.88) | 11.87 (0.93) | <.001 |
| Gestation at last haemoglobin (wk) | 7270 | 34.5 (3.1) | 34.3 (3.0) | 34.3 (3.1) | 34.2 (3.1) | 34.4 (3.2) | .13 |
| Late pregnancy anaemia | 7270 | ||||||
| No | 5006 | 52.7 | 63.5 | 71.8 | 75.6 | 85.1 | <.001 |
| Yes | 2264 | 47.3 | 36.5 | 28.2 | 24.4 | 14.9 | |
| Hayfever | 6189 | ||||||
| No | 5639 | 90.3 | 91.2 | 90.8 | 91.1 | 92.3 | |
| Yes | 550 | 9.7 | 8.8 | 9.2 | 8.9 | 7.7 | .53 |
| Eczema | 6204 | ||||||
| No | 5177 | 83.8 | 83.8 | 83.1 | 82.5 | 83.9 | |
| Yes | 1027 | 16.2 | 16.2 | 16.9 | 17.5 | 16.1 | .85 |
| Wheezing | 6219 | ||||||
| No | 5551 | 89.3 | 88.6 | 89.0 | 88.7 | 90.7 | |
| Yes | 668 | 10.7 | 11.4 | 11.0 | 11.3 | 9.3 | .48 |
| Asthma | 6163 | ||||||
| No | 4895 | 80.0 | 77.3 | 81.2 | 79.3 | 79.8 | |
| Yes | 1268 | 20.0 | 22.7 | 18.8 | 20.7 | 20.2 | .19 |
| Allergic sensitisation | 4956 | ||||||
| No | 3908 | 78.6 | 75.9 | 80.5 | 80.2 | 79.7 | |
| Yes | 1048 | 21.4 | 24.1 | 19.5 | 19.8 | 20.3 | .07 |
| IgE (ku/L)a | 3772 | 59.7 (20.9, 179.0) | 55.5 (21.2, 210.0) | 55.4 (21.4, 178.0) | 60.3 (21.3, 189.0) | 59.5 (18.2, 201.0) | .83 |
| FEV1 SD scoreb | 5076 | 0.02 (1.00) | 0.01 (1.00) | 0.00 (0.98) | 0.03 (1.00) | −0.02 (0.99) | .97 |
| FVC SD scoreb | 5149 | 0.00 (1.00) | 0.00 (1.00) | 0.04 (0.99) | 0.01 (0.99) | −0.01 (1.00) | .80 |
| FEF25‐75 SD scoreb | 5149 | 0.02 (0.98) | 0.01 (0.97) | −0.04 (1.02) | 0.01 (1.00) | 0.00 (1.03) | .65 |
| Gender | 7270 | ||||||
| Male | 3749 | 51.8 | 52.6 | 51.8 | 49.6 | 51.9 | |
| Female | 3521 | 48.2 | 47.4 | 48.2 | 50.4 | 48.1 | .55 |
| Multiple pregnancy | 7270 | ||||||
| Singleton | 7106 | 96.5 | 98.6 | 97.4 | 98.2 | 98.2 | |
| Twin | 164 | 3.5 | 1.4 | 2.6 | 1.8 | 1.8 | .001 |
| Maternal ethnicity | 6960 | ||||||
| White | 6829 | 96.8 | 98.1 | 98.5 | 98.6 | 98.8 | |
| Non‐white | 131 | 3.2 | 1.9 | 1.5 | 1.4 | 1.2 | <.001 |
| Maternal BMI (kg/m2) | 6563 | 22.36 (3.48) | 22.66 (3.41) | 22.93 (3.66) | 23.21 (3.74) | 23.84 (4.48) | <.001 |
| Maternal age (y) | 7270 | 28.93 (4.63) | 28.93 (4.49) | 28.79 (4.58) | 28.78 (4.61) | 28.34 (4.64) | .003 |
| Maternal parity | 7014 | ||||||
| Nulliparous | 3304 | 41.8 | 43.7 | 47.3 | 49.3 | 54.9 | |
| Multiparous | 3710 | 58.2 | 56.3 | 52.7 | 50.7 | 45.1 | <.001 |
| Maternal smoking in pregnancy | 7069 | ||||||
| Never | 5146 | 70.4 | 74.5 | 73.4 | 73.7 | 72.3 | |
| 1st trimester | 857 | 12.1 | 12.2 | 13.6 | 11.2 | 11.6 | |
| Throughout | 1066 | 17.5 | 13.3 | 13.0 | 15.1 | 16.1 | .01 |
| Maternal education | 6991 | ||||||
| CSE/vocational | 1720 | 25.1 | 23.6 | 23.6 | 24.8 | 25.8 | |
| O level | 2510 | 35.4 | 36.0 | 34.8 | 35.9 | 37.4 | |
| A level | 1739 | 25.1 | 26.4 | 24.8 | 23.2 | 24.6 | |
| Degree | 1022 | 14.3 | 14.1 | 16.7 | 16.1 | 12.1 | .11 |
| Maternal asthma | 7002 | ||||||
| No | 6242 | 91.3 | 90.2 | 88.2 | 87.8 | 87.6 | |
| Yes | 760 | 8.7 | 9.8 | 11.8 | 12.2 | 12.4 | .003 |
| Maternal eczema | 7002 | ||||||
| No | 5370 | 77.1 | 78.9 | 78.0 | 74.7 | 74.7 | |
| Yes | 1632 | 22.9 | 21.1 | 22.0 | 25.3 | 25.3 | .02 |
| Gestational age (wk)a | 7270 | 40 (39, 41) | 40 (39, 41) | 40 (39, 41) | 40 (39, 41) | 40 (39, 41) | .92 |
| Birthweight (g) | 7213 | 3442.4 (536.3) | 3456.0 (509.1) | 3445.0 (527.6) | 3446.3 (533.2) | 3404.2 (557.1) | .10 |
a
Median (interquartile range) is presented due to the skewed distributions of these variables.
b
Lung function SD scores are standardised by age, sex and height.