Table 2.

Thyroid function measures by time point and difference over time, by intervention arm

Measure	TC arm (median [Q1–Q3])	nTC arm (median [Q1–Q3])	P c
TSH (μl/mL)
Baseline a	1.19 [0.82–1.38]	1.23 [0.77–1.56]	0.65
Late pregnancy	1.45 [1.07–2.33]	1.44 [1.11–2.00]	0.82
Post delivery	0.89 [0.81–1.08]	0.95 [0.73–1.58]	0.94
Difference b from baseline	0.34 [−0.02 – 0.56]	0.51 [0.1 – 0.91]	0.26 d
T3 (ng/dL)
Baseline	144 [117–167]	144 [113–156]	0.57
Late pregnancy	131 [123–154]	141 [134–157]	0.14
Post delivery	109 [94–110]	100 [95.5–108]	0.94
Difference from baseline	−14 [−27 –8]	−0.5 [−14–28]	0.24 d
TT4 (μg/dL)
Baseline	12.3 [10.7–14.8]	12.1 [10.9–13.5]	0.54
Late pregnancy	11.8 [10.7–13.2]	11.3 [10.2–12.6]	0.34
Post delivery	7.5 [7.3–7.9]	8.0 [6.7–8.9]	0.71
Difference from baseline	−0.4 [−1.6 – 0.4]	−0.9 [−2.5 – 0.4]	0.32 d
FT4 (ng/dL)
Baseline	0.9 [0.9–1.0]	0.9 [0.9–1.0]	0.48
Late pregnancy	0.9 [0.9–1.0]	0.9 [0.8–1.0]	0.11
Post delivery	0.9 [0.9–1.0]	0.95 [0.85–1.05]	1.00
Difference from baseline	0 [−0.1 – 0]	−0.1 [−0.1 – 0]	0.12 d

TSH: thyrotropin, T3: total triiodothyronine; TT4 and FT4: total and free thyroxine

^aBaseline: approximately 23 weeks gestation (51 women in the TC arm and 45 in the nTC arm); late pregnancy: approximately 36 weeks gestation (29 in each arm); post-delivery: approximately 8 weeks (5 in the TC arm and 8 in the nTC arm)

^bAmong women with two pre-delivery measures only (25 women in the TC arm and 24 in the nTC arm)

^cWilcoxon rank-sum test unless otherwise indicated

^dT-test