Table 3.
Results according to the duration of iodine containing (≥150 μg/day) pregnancy supplement consumption
| Nonusers (n = 74) | Pregnancy starters (n = 51) | Prepregnancy starters (n = 27) | p valuea | |
|---|---|---|---|---|
| Start of iodine supplementation | n.a. | At the time of detection of pregnancy | At least 4 weeks before pregnancy | n.a. |
| Duration (weeks) | 0 | 10 (5–12) | 25 (20–33) | <.001 |
| Age (years) | 29.8 ± 5.8 | 30.2 ± 5.3 | 30.9 ± 4.0 | .641 |
| UIC (μg/L) | 130 (75–212) | 240 (145–360) | 205 (104–492) | <.001 |
| UIC/Cr (μg/g creatinine) | 113 (84–199) | 193 (131–315) | 202 (128–289) | <.001 |
| Tg (μg/L) | 14.6 (10.7–26.2) | 14.5 (8.3–26.3) | 9.1 (4.8–20.4) | .022 |
| Tg ≥44 μg/L (n) | 6 (8%) | 5 (10%) | 1 (4%) | .634 |
| TSH (mU/L) | 1.62 (0.99–2.01) | 1.97 (1.4–2.78) | 1.72 (1.03–2.63) | .006 |
| fT4 (pmol/L) | 13.3 (12.5–14.4) | 13.2 (12.5–14.3) | 13.9 (12.0–14.7) | .923 |
| fT3 (pmol/L) | 4.8 (4.4–5.0) | 4.6 (4.3–5.0) | 4.8 (4.5–5.1) | .282 |
| hCG (IU/L) | 28391 (21645–40760) | 33029 (20801–44414) | 34856 (27267–43289) | .419 |
| Iodized salt consumption (n) | 26 (35%) | 21 (41%) | 14 (52%) | .311 |
| Smokers (n) | 23 (31%) | 14 (28%) | 5 (19%) | .458 |
Note. Age is expressed as mean ± standard deviation; laboratory parameters and the duration of iodine supplement use are expressed as median and interquartile range (in parenthesis). UIC = urinary iodine concentration; UIC/Cr = creatinine‐normalized urinary iodine concentration; Tg = thyroglobulin; TSH = thyroid‐stimulating hormone; fT4 = free thyroxine; fT3 = free triiodothyronine; hCG = human chorionic gonadotropin; n.a. = not applicable.
a
Analysis of variance (age), chi‐square test (rate of smoking and Tg ≥44 μg/L), and Kruskal–Wallis H test (other parameters).