Comparison of Southampton Women's Survey mother–child pairs with complete data with those lacking either maternal 25-hydroxyvitamin D or 6-year follow-up data but born in the same time period
| Mother–child pairs in analysis (n= 860) | Mother–child pairs with missing data (n= 625) | p Value | |
| Maternal characteristics | |||
| Age at child's birth, mean (SD) | 30.37 (3.81) | 29.63 (3.76) | <0.001 |
| Primiparous, n (%) | |||
| No | 462 (53.72) | 369 (59.04) | 0.042 |
| Yes | 398 (46.28) | 256 (40.96) | |
| Qualifications, n (%) | |||
| None | 14 (1.63) | 35 (5.61) | 0.001 |
| GCSE D–G | 84 (9.78) | 67 (10.74) | |
| GCSE A*–C | 248 (28.87) | 179 (28.69) | |
| A Level | 249 (28.99) | 186 (29.81) | |
| HND | 64 (7.45) | 40 (6.41) | |
| Degree | 200 (23.28) | 117 (18.75) | |
| Parents' social class, n (%) | |||
| 1 | 88 (10.35) | 57 (12.26) | 0.031 |
| 2 | 425 (50.00) | 201 (43.23) | |
| 3N | 234 (27.53) | 123 (26.45) | |
| 3M | 67 (7.88) | 54 (11.61) | |
| 4 | 34 (4.00) | 23 (4.95) | |
| 5 | 2 (0.24) | 7 (1.51) | |
| Smoked in pregnancy, n (%) | |||
| No | 723 (85.46) | 469 (78.17) | <0.001 |
| Yes | 123 (14.54) | 131 (21.83) | |
| Maternal asthma, n (%) | |||
| No | 673 (78.9) | 468 (75.97) | 0.184 |
| Yes | 180 (21.1) | 148 (24.03) | |
| Maternal childhood eczema, n (%) | |||
| No | 703 (82.51) | 501 (81.33) | 0.561 |
| Yes | 149 (17.49) | 115 (18.67) | |
| Maternal rhinitis, n (%) | |||
| No | 494 (57.91) | 372 (60.39) | 0.341 |
| Yes | 359 (42.09) | 244 (39.61) | |
| Maternal atopy, n (%) | |||
| No | 406 (53.28) | 255 (56.67) | 0.253 |
| Yes | 356 (46.72) | 195 (43.33) | |
| Pre-pregnancy body mass index (kg/m2), median (IQR) | 24.32 (22.01–27.53) | 24.05 (21.93–27.35) | 0.996 |
| Height (cm), mean (SD) | 163.50 (6.65) | 162.81 (6.01) | 0.041 |
| Serum 25-hydroxyvitamin D (nmol/litre), median (IQR) | 59.00 (40.52–84.89) | 53.00 (38.47–79.19) | 0.027 |
| Paternal characteristics | |||
| Paternal asthma, n (%) | |||
| No | 697 (82.39) | 486 (80.46) | 0.351 |
| Yes | 149 (17.61) | 118 (19.54) | |
| Paternal childhood eczema, n (%) | |||
| No | 739 (88.29) | 531 (88.06) | 0.893 |
| Yes | 98 (11.71) | 72 (11.94) | |
| Paternal rhinitis, n (%) | |||
| No | 558 (66.59) | 400 (66.12) | 0.852 |
| Yes | 280 (33.41) | 205 (33.88) | |
| Child's characteristics | |||
| Gender, n (%) | |||
| Boy | 445 (51.74) | 333 (53.45) | 0.516 |
| Girl | 415 (48.26) | 290 (46.55) | |
| Birth weight (kg), mean (SD) | 3483.63 (494.52) | 3467.09 (498.12) | 0.529 |
| Gestational age, (weeks), median (IQR) | 40.14 (39.14–41.00) | 40.14 (39.14–41.00) | 0.914 |
| Months of breastfeeding, n (%) | |||
| None | 132 (15.70) | 131 (23.69) | <0.001 |
| <1 | 168 (19.98) | 116 (20.98) | |
| 1–3 | 157 (18.67) | 122 (22.06) | |
| 4–6 | 156 (18.55) | 72 (13.02) | |
| 7–11 | 139 (16.53) | 81 (14.65) | |
| 12 or more | 89 (10.58) | 31 (5.61) | |
| Age of introducing solid food (weeks), median (IQR) | 17.38 (15.04–17.67) | 17.38 (15.04–17.38) | 0.282 |
| Mother smoked during child's infancy, n (%) | |||
| No | 707 (82.88) | 439 (76.88) | 0.005 |
| Yes | 146 (17.12) | 132 (23.12) | |
| Cats/dogs in home during child's infancy, n (%) | |||
| No | 432 (50.47) | 295 (53.25) | 0.307 |
| Yes | 424 (49.53) | 259 (46.75) | |
| Age at testing (years), median (IQR) | 6.46 (6.34–6.61) | 6.44 (6.35–6.60) | 0.797 |