Table 1.
Characteristics and thyroid hormone levels of the mother–child pairs (n = 499).
| Characteristic | n (%) or mean (10th–90th percentile) |
|---|---|
| Mothers | |
| Age (years) | 29.1 (23–35) |
| Prepregnancy BMI (kg/m2) | 23.9 (19.6–29.8) |
| Educationa | |
| Low | 61 (12.3%) |
| Middle | 182 (36.5%) |
| High | 256 (51.2%) |
| Self-reported smoking status | |
| Never-smoker | 316 (63.2%) |
| Cessation before pregnancy | 113 (22.7%) |
| Smoker during pregnancy | 70 (14.1%) |
| Self-reported passive indoor smoking (n = 486) | 43 (8.8%) |
| Alcohol consumption (n = 485) | |
| None | 398 (82.1%) |
| Occasionally | 87 (17.9%) |
| Parity | |
| 1 | 275 (55.0%) |
| 2 | 170 (34.1%) |
| ≥ 3 | 54 (10.9%) |
| Newborns | |
| Sex | |
| Female | 254 (50.8%) |
| European-Caucasian ethnicityb | 435 (87.2%) |
| Gestational age (weeks) | 39.4 (38–41) |
| Season of delivery | |
| Winter (December–March) | 142 (28.5%) |
| Spring (March–June) | 113 (22.7%) |
| Summer (June–September) | 107 (21.4%) |
| Autumn (September–December) | 137 (27.4%) |
| Apgar score 5 min after birth | |
| 7 or 8 | 39 (7.8%) |
| 9 | 140 (28.1%) |
| 10 | 320 (64.1%) |
| pH of arterial cord blood (n = 431) | 7.2 (7.2–7.3) |
| Birth weight (g) | 3,446 (2,915–3,990) |
| Minutes of labor (n = 427) | 27.3 (8–54) |
| Cord blood thyroid hormones | |
| TSH, mU/L | 10.3 (5.5–22.3) |
| FT3, pmol/L | 2.5 (2.0–3.2) |
| FT4, pmol/L | 15.7 (13.5–18.5) |
| Ratio FT4/FT3 | 6.4 (5.0–8.0) |
| Maternal thyroid hormones (n = 431)c | |
| TSH, mU/L | 2.1 (1.1–4.0) |
| FT3, pmol/L | 4.2 (3.4–5.1) |
| FT4, pmol/L | 12.5 (10.0–15.2) |
| Ratio FT4/FT3 | 3.0 (2.4–3.8) |
| For TSH, FT3, and FT4 levels, the geometric mean (10th–90th percentile) is given. aMother’s education: low (no high school diploma), middle (high school diploma), high (college or university diploma). bBased on the native country of the newborn’s grandparents. European-Caucasian when two or more grandparents were European, or non-European when at least three grandparents were of non-European origin. cTotal group minus mothers from whom blood samples were not available. | |