Table 1.
Characteristics of included mothers categorized by low and high (median split) iodine (urinary concentrations, UIC) and selenium (plasma concentrations, P-Se) status.
| Characteristics | n (% within group) and/or median (5−95th percentile) | ||||||
|---|---|---|---|---|---|---|---|
| All | UIC1 | p | P-Se2 | p | |||
| Mothers | n = 604 | Low n = 294 | High n = 294 | Low n = 295 | High n = 295 | ||
| Age (years) | 30 (23–39) | 30 (23–39) | 30 (24–39) | 0.470 | 30 (23–39) | 30 (24–39) | 0.272 |
| Missing | 1 | – | 1 | – | 1 | ||
| Early-pregnancy BMI (kg/m2) | 24.3 (19.4–35.0) | 24.7 (19.6–35.9) | 24.3 (19.2–34.2) | 0.053 | 24.7 (19.9–35.8) | 24.2 (19.3–34.5) | 0.018 |
| Underweight (<18.5) | 10 (2) | 5 (2) | 4 (1) | 0.049t | 5 (2) | 4 (1) | 0.032t |
| Normal weight (18.5–24.9) | 327 (56) | 148 (52) | 166 (58) | 144 (51) | 171 (59) | ||
| Overweight (25.0–29.9) | 163 (28) | 81 (28) | 81 (28) | 84 (29) | 78 (27) | ||
| Obesity (≥30.0) | 88 (15) | 53 (18) | 34 (12) | 52 (18) | 36 (12) | ||
| Missing | 16 | 7 | 9 | 10 | 6 | ||
| Education | |||||||
| Elementary school, 9 year | 13 (2) | 8 (3) | 5 (2) | 0.134 | 10 (4) | 3 (1) | 0.066 |
| High school, 12 year | 167 (28) | 91 (31) | 71 (25) | 0.046t | 85 (29) | 75 (26) | 0.041t |
| University or other, >12 year | 416 (70) | 193 (66) | 212 (74) | 194 (67) | 215 (73) | ||
| Missing | 8 | 2 | 6 | 6 | 2 | ||
| Smoking before pregnancy (yes) | 37 (6) | 21 (7) | 16 (5) | 0.401f | 21 (7) | 16 (6) | 0.497f |
| Missing | 8 | 5 | 3 | 3 | 5 | ||
| Vegetarian (yes) | |||||||
| Pregnancy, GW34 | 9 (2) | 4 (1) | 5 (2) | 1.000f | 8 (3) | 1 (<1) | 0.019f |
| Missing | 32 | 14 | 12 | 18 | 10 | ||
| Postpartum, 4M | 7 (1) | 4 (1) | 3 (1) | 1.000f | 6 (2) | 1 (<1) | 0.123f |
| Missing | 57 | 27 | 29 | 27 | 30 | ||
| Pescatarian (yes) | |||||||
| Pregnancy, GW34 | 10 (2) | 1 (<1) | 9 (3) | 0.020f | 2 (1) | 8 (3) | 0.107f |
| Missing | 32 | 14 | 12 | 18 | 10 | ||
| Postpartum, 4M | 14 (3) | 2 (1) | 11 (4) | 0.012f | 3 (1) | 10 (4) | 0.053f |
| Missing | 57 | 27 | 29 | 27 | 30 | ||
| Omnivores (yes) | |||||||
| Pregnancy, GW34 | 553 (97) | 275 (98) | 268 (95) | 0.059f | 267 (96) | 276 (97) | 0.819f |
| Missing | 32 | 14 | 12 | 18 | 10 | ||
| Postpartum, 4M | 526 (96) | 261 (98) | 251 (95) | 0.072f | 259 (97) | 254 (96) | 0.656f |
| Missing | 57 | 27 | 29 | 27 | 30 | ||
| Supplement use (yes)3 | |||||||
| Pregnancy, GW34 | 232 (41) | 65 (23) | 159 (56) | <0.001f | 71 (26) | 156 (55) | <0.001f |
| Missing | 32 | 14 | 12 | 18 | 10 | ||
| Postpartum, 4M | 100 (18) | 28 (10) | 70 (26) | <0.001f | 31 (12) | 68 (26) | <0.001f |
| Missing | 57 | 27 | 29 | 27 | 30 | ||
| Iodized salt use (yes) | 388 (86) | 182 (84) | 198 (88) | 0.279f | 192 (86) | 187 (85) | 0.685f |
| Missing | 151 | 77 | 68 | 73 | 75 | ||
Divided into two groups with median split of maternal urinary iodine concentrations at gestational week 29. Low includes values ≤ 113.4 μg/L and high >113.4 μg/L.
Divided into two groups with median split of maternal plasma selenium concentrations at gestational week 29. Low includes values ≤ 64.73 μg/kg and high >64.73 μg/kg.
Regular use (every day or several days a week) of multivitamins with minerals. Differences in distribution between low and high groups were tested with Fisher's exact test and Pearson Chi-Square for categorical variables, and Mann-Whitney U test for continuous variables.
Linear-by-linear association.
Fisher's exact test.