Table 1.
Maternal Characteristics at Baseline.*
| Characteristic | Subclinical Hypothyroidism | Hypothyroxinemia | ||
|---|---|---|---|---|
| Levothyroxine (N = 339) | Placebo (N = 338) | Levothyroxine (N = 265) | Placebo (N = 261) | |
| Age — yr | 27.7±5.7 | 27.3±5.7 | 27.8±5.7 | 28.0±5.8 |
|
| ||||
| Race or ethnic group — no. (%)† | ||||
|
| ||||
| Black | 27 (8) | 25 (7) | 61 (23) | 65 (25) |
|
| ||||
| Hispanic | 195 (58) | 185 (55) | 131 (49) | 125 (48) |
|
| ||||
| White | 109 (32) | 117 (35) | 69 (26) | 69 (26) |
|
| ||||
| Other | 8 (2) | 11 (3) | 4 (2) | 2 (1) |
|
| ||||
| Body-mass index‡ | 28.1±6.4 | 28.2±6.4 | 30.3±6.4 | 30.2±7.1 |
|
| ||||
| Nulliparous — no. (%) | 124 (37) | 134 (40) | 69 (26) | 64 (25) |
|
| ||||
| Baseline thyrotropin — mU/liter | ||||
|
| ||||
| Median | 4.5 | 4.3 | 1.5 | 1.4 |
|
| ||||
| 95% CI | 4.4–4.7 | 4.2–4.5 | 1.4–1.6 | 1.3–1.5 |
|
| ||||
| Baseline free thyroxine — ng/dl§ | ||||
|
| ||||
| Median | 1.01 | 1.02 | 0.83 | 0.83 |
|
| ||||
| 95% CI | 1.00–1.02 | 1.01–1.04 | 0.82–0.83 | 0.82–0.83 |
|
| ||||
| Urinary iodine — μg/liter¶ | ||||
|
| ||||
| Median | 199 | 196 | 185 | 191 |
|
| ||||
| 95% CI | 184–238 | 172–229 | 167–219 | 164–208 |
| No. of weeks of gestation at randomization | 16.6±3.0 | 16.7±3.0 | 18.0±2.8 | 17.7±2.9 |
*
Plus–minus values are means ±SD. There were no significant differences at baseline between the levothyroxine group and the placebo group in either trial (P>0.05). CI denotes confidence interval.
†
Race and ethnic group were determined by the research nurses.
‡
The body-mass index is the weight in kilograms divided by the square of the height in meters.
§
To convert thyroxine values to picomoles per liter, multiply by 12.87.
¶
One patient in the levothyroxine group and one in the placebo group in the subclinical hypothyroidism trial were missing the urinary iodine measurement.