0 usually) before pregancy on a stable dose
of a levothyroxine product (brand preferred
in pregnancy for consistency), with expectation
of increasing the dose by 25-40% during pregnancy (usually within first 16 weeks).
Test TSI during second trimester - if >3-5 x higher than upper end of normal (not common), then fetal ultrasound and close following with high-risk OB is usually indicated.