Table 2.

Summary of the most important RCTs evaluating effects of levothyroxine replacement in women who are euthyroid with raised TPO antibodies before and during pregnancy.

Trial	Country	Population	Intervention	Control	Primary outcome	Events intervention group	Events control group	Results
Wang 201719	China	N=600 women (N=300 intervention and N=300 control) undergoing IVF-ET. TPO raised and biochemically euthyroid	Levothyroxine to titrate TSH: 0.1–2.5 mIU/L in first trimester 0.2–3.0 mIU/L in second trimester 0.3–3.0mIU/L in third trimester	No treatment	Miscarriage before 28 weeks’ gestation in women becoming pregnant	10.3%	10.6%	Absolute RD = -0.34% 95% CI= -8.65– 8.12%
Dhillon-Smith 201918	UK	N=940 women with history of miscarriage or infertility (N=476 intervention and N=476 control). TPO raised and biochemically euthyroid	Levothyroxine 50 µg OD	Placebo	Live birth after 34 weeks’ gestation	37.4%	37.9%	P value=0.74 RR=0.97 95% CI= 0.83–1.14 Absolute RD= -0.4% [-6.6–5.8]
Van Dijk 202317	The Netherlands, Belgium, Denmark	N=187 women with two or more pregnancy losses (N=94 intervention and N=93 control). TPO raised and biochemically euthyroid	Levothyroxine 0.5–1.0 µg/kg depending on pre-conception TSH	Placebo	Live birth after 24 weeks’ gestation	50%	48%	RR=1.03 95% CI= 0.77–1.38

RD, Rate difference, RR, Relative risk, CI, Confidence interval.