Table 1.
Sociodemographic, lifestyle, and clincial characteristics of the 462 mother-neonate pairs and by tertiles of placental iodine concentration
| Characteristics | Total (n = 462) | Tertile 1 (n = 154) | Tertile 2 (n = 154) | Tertile 3 (n = 154) | p value for trend |
|---|---|---|---|---|---|
| Mother | |||||
| Age, years | 29.5 (4.4) | 29.3 (3.9) | 29.5 (4.8) | 29.6 (4.5) | 0.75 |
| Pre-pregnancy BMI, kg/m2 | 24.5 (4.7) | 24.8 (5.0) | 24.6 (4.6) | 24.2 (4.7) | 0.54 |
| Gestational weight gain, kg | 13.8 (5.7) | 14.5 (5.7) | 13.9 (5.6) | 13.0 (5.9) | 0.07 |
| Hypertension | 0.35 | ||||
| Yes | 27 (5.8%) | 6 (3.9%) | 12 (7.8%) | 9 (5.8%) | |
| Smoking status | 0.08 | ||||
| Never-smoker | 298 (64.5%) | 87 (56.5%) | 107 (69.5%) | 104 (67.5%) | |
| Cessation before pregnancy | 122 (26.4%) | 53 (34.4%) | 32 (20.8%) | 37 (24.0%) | |
| Current smoker | 42 (9.1%) | 14 (9.1%) | 15 (9.7%) | 13 (8.5%) | |
| Exposure to indoor second-hand smoke | 0.32 | ||||
| Yes | 26 (5.6%) | 12 (7.8%) | 6 (3.9%) | 8 (5.2%) | |
| Alcohol consumptiona | 0.50 | ||||
| None | 400 (86.6%) | 130 (84.4%) | 133 (86.4%) | 137 (89.0%) | |
| ≤2 glasses per week | 62 (13.4%) | 24 (15.6%) | 21 (13.6%) | 17 (11.0%) | |
| Educationb | 0.58 | ||||
| Low | 59 (12.8%) | 20 (13.0%) | 24 (15.6%) | 15 (9.7%) | |
| Middle | 153 (33.1%) | 54 (35.0%) | 47 (30.5%) | 52 (33.6%) | |
| High | 250 (54.1%) | 80 (52.0%) | 83 (53.9%) | 87 (56.8%) | |
| Multi-vitamin use | 0.12 | ||||
| Yes | 259 (56.1%) | 77 (50.0%) | 87 (56.5%) | 95 (61.7%) | |
| Fish consumption | 0.63 | ||||
| Never | 34 (7.4%) | 14 (9.1%) | 8 (5.2%) | 12 (7.8%) | |
| Less than once per week | 205 (44.4%) | 66 (42.9%) | 74 (48.1%) | 65 (42.2%) | |
| At least once per week | 223 (48.2%) | 74 (48.0%) | 72 (46.8%) | 77 (50.0%) | |
| Fruit and vegetable consumption | 0.58 | ||||
| Less than once per day | 55 (11.9%) | 17 (11.0%) | 16 (10.4%) | 22 (14.3%) | |
| Once per day | 146 (31.6%) | 50 (32.5%) | 54 (35.1%) | 42 (27.3%) | |
| More than once per day | 261 (56.5%) | 87 (56.5%) | 84 (54.6%) | 90 (58.4%) | |
| Neonate | |||||
| Gestational age, weeks | 39.9 (1.0) | 39.8 (1.1) | 39.8 (1.0) | 40.1 (0.9) | 0.07 |
| Birth weight, g | 3458 (426) | 3472 (465) | 3426 (431) | 3476 (378) | 0.51 |
| Birth length, cm | 50.3 (1.9) | 50.4 (1.9) | 50.2 (1.8) | 50.4 (1.8) | 0.75 |
| Sex | 0.48 | ||||
| Male | 237 (51.3%) | 77 (50.0%) | 85 (55.2%) | 75 (48.7) | |
| Ethnicity | 0.78 | ||||
| European | 403 (87.2%) | 135 (87.7%) | 136 (88.3%) | 132 (85.7%) | |
| Parity | 0.83 | ||||
| 1 | 244 (52.8%) | 79 (51.3%) | 80 (52.0%) | 85 (55.2%) | |
| 2 | 156 (33.8%) | 51 (33.1%) | 53 (34.4%) | 52 (33.8%) | |
| ≥3 | 62 (13.4%) | 24 (15.6%) | 21 (13.6%) | 17 (11.0%) | |
| Season at delivery | 0.04 | ||||
| Winter (Dec 21 to March 20) | 105 (22.7%) | 24 (15.6%) | 42 (27.3%) | 39 (25.3%) | |
| Spring (March 21 to June 20) | 111 (24.0%) | 34 (22.0%) | 44 (28.6%) | 33 (21.4%) | |
| Summer (June 21 to Sept 20) | 133 (28.8%) | 48 (31.2%) | 37 (24.0%) | 48 (31.2%) | |
| Autumn (Sept 21 to Dec 20) | 113 (24.5%) | 48 (31.2%) | 31 (20.1%) | 34 (22.1%) | |
| Placental iodine concentration, µg/kg | 26.1 (4.3) | 21.6 (2.0) | 25.8 (1.0) | 30.8 (2.7) | - |
Data are presented as mean (SD) or n (%). Tertiles are based on the placental iodine concentration: I ≤ 24.2; 24.2 < I ≤ 27.5; and I > 27.5
aFor full details, please see the population characteristics in the results section
bCoded as ‘low’ (no diploma or primary school), ‘middle’ (high school) and ‘high’ (college or university degree)
cClassification of ethnicity is based on the native country of the neonates' grandparents as either European (at least two grandparents were European) or non-European (at least three grandparents were of non-European origin)