Table 3 Interaction term analyses between FT4 or TSH concentrations and gestational age at the thyroid function test on risk of preterm birth
Interaction term | Total sample | Women with a test ≤18 weeks of gestation | Women with a test > 18 weeks of gestation | |||
|---|---|---|---|---|---|---|
OR (95% CI) | P value | OR (95% CI) | P value | OR (95% CI) | P value | |
FT4 concentrations (pmol/L) | 0.98 (0.92–1.04) | 0.44 | 1.13 (1.00–1.28) | 0.044 | 0.68 (0.48–0.97) | 0.035 |
Gestational age at the test (weeks) | 0.98 (0.93–1.03) | 0.34 | 1.15 (1.01–1.32) | 0.038 | 0.82 (0.70–0.97) | 0.017 |
FT4 by gestational age at test | 1.00 (1.00–1.01) | 0.58 | 0.99 (0.98–1.00) | 0.032 | 1.02 (1.00–1.03) | 0.025 |
TSH concentrations (uIU/mL) | 1.04 (0.92–1.18) | 0.90 | 0.97 (0.74–1.25) | 0.79 | 0.95 (0.55–1.64) | 0.84 |
Gestational age at the test (weeks) | 1.00 (0.98–1.02) | 0.50 | 1.00 (0.96–1.04) | 0.99 | 0.99 (0.94–1.04) | 0.65 |
TSH by gestational age at test | 1.00 (0.99–1.00) | 0.26 | 1.00 (0.98–1.02) | 0.89 | 1.00 (0.98–1.02) | 0.90 |