Table 1.
Demographic characteristics of women with TSH, TT4, and FT4 data.
| TSH | TT4 | FT4 | |
|---|---|---|---|
| N | 1707 | 1791 | 1766 |
| Maternal age (years; mean; SD) | 32.1 (5.1) | 32.1 (5.0) | 32.1 (5.1) |
| Race (n; %) | |||
| White | 1465 (85.8) | 1536 (85.8) | 1517 (85.9) |
| Other | 242 (14.2) | 255 (14.2) | 249 (14.1) |
| Marital status (n; %) | |||
| Married or common law | 1624 (95.1) | 1702 (95.0) | 1677 (95.0) |
| Single | 83 (4.9) | 89 (5.0) | 89 (5.0) |
| Level of education (n; %) | |||
| College diploma or less | 644 (37.7) | 679 (37.9) | 673 (38.1) |
| University degree | 1063 (62.3) | 1112 (62.1) | 1093 (61.9) |
| Household income (n; %) | |||
| <100,000 | 985 (60.4) | 1034 (60.4) | 1020 (60.4) |
| ≥100,000 | 646 (39.6) | 678 (39.6) | 668 (39.6) |
| City (n; %) | |||
| Fluoridateda | 1041 (61.0) | 1091 (60.9) | 1074 (60.8) |
| Non-fluoridatedb | 666 (39.0) | 700 (39.1) | 692 (39.2) |
| Second-hand smoke in trimester 1 (n; %) | |||
| Yes | 107 (6.3) | 110 (6.2) | 109 (6.2) |
| No | 1599 (93.7) | 1680 (93.8) | 1656 (93.8) |
| Pre-pregnancy BMI (kg/m2; mean; SD) | 24.8 (5.4) | 24.8 (5.4) | 24.8 (5.4) |
| Parity (n; %) | |||
| 0 | 760 (44.5) | 799 (44.6) | 790 (44.7) |
| 1 | 686 (40.2) | 719 (40.2) | 707 (40.0) |
| 2+ | 261 (15.3) | 273 (15.2) | 269 (15.3) |
| Gestational age (weeks; mean; SD)c | 11.6 (1.5) | 11.6 (1.5) | 11.6 (1.5) |
| Maternal fluoride exposure | |||
| MUFSG (mg/L; mean; SD) | 0.59 (0.41) | 0.59 (0.41) | 0.59 (0.41) |
| Water fluoride (mg/L; mean; SD) | 0.42 (0.25) | 0.42 (0.25) | 0.42 (0.25) |
| Maternal thyroid hormones | |||
| TSH (log; mean; SD) | −0.01 (0.96) | −0.01 (0.96) | −0.00 (0.95) |
| TSH (μIU/mL; mean; SD) | 1.3 (0.98) | 1.3 (0.98) | 1.3 (0.98) |
| FT4 (log; mean; SD) | 2.6 (0.20) | 2.6 (0.20) | 2.6 (0.20) |
| FT4 (pg/mL; mean; SD) | 13.6 (4.5) | 13.6 (4.4) | 13.6 (4.4) |
| TT4 (ng/mL; mean; SD) | 106.2 (21.3) | 106.3 (21.4) | 106.2 (21.2) |
| Maternal thyroid antibodies | |||
| Anti-Tg (IU/mL; mean; SD) | 10.4 (50.4) | 10.2 (49.5) | 10.1 (49.8) |
| Anti-TPO (IU/mL; mean; SD) | 20.6 (86.9) | 20.8 (88.6) | 20.0 (86.7) |
| Anti-TPO + (≥5.61 IU/mL; n; %) | 216 (12.8) | 222 (12.7) | 214 (12.4) |
| Maternal iodine status | |||
| Plasma Tg (ng/mL; median; IQR) | 13.7 (13.1) | 13.8 (13.2) | 13.7 (13.0) |
| UIC unadjusted (μg/L; median; IQR) | 182.3 (179.4) | 182.3 (177.8) | 183.5 (177.2) |
| UICSG (μg/L; median; IQR) | 191.7 (128.5) | 191.9 (129.8) | 191.1 (128.3) |
| UIC/Cr (μg/g; median; IQR) | 299.0 (216.6) | 300.2 (219.5) | 299.4 (219.3) |
| Child sex (n; %) | |||
| Male | 899 (54.0) | 948 (54.2) | 931 (54.0) |
| Female | 765 (46.0) | 800 (45.8) | 792 (46.0) |
Due to missing data, percentage totals for subgroups may not sum to the total sample population; percentages are reported based on total sample in each subgroup with available data.
a
Edmonton, Winnipeg, Toronto, Hamilton, Sudbury, Ottawa, Halifax.
b
Vancouver, Kingston, Montreal.
c
Gestational age at time of maternal blood collection in trimester one (T1).
Abbreviations: SD= standard deviation; MUFSG = maternal urinary fluoride, adjusted for specific gravity; TSH= thyroid stimulating hormone; FT4= free thyroxine; TT4= total thyroxine; Tg= thyroglobulin; TPO = thyroid peroxidase; UICSG = urinary iodine concentration, adjusted for specific gravity.
Means represent geometric means.