“The number that changed when she conceived”

The same TSH that means "monitor, don’t treat" in a non-pregnant woman means "act now" in early pregnancy with positive TPO antibodies — NICE NG145 does not cover pregnancy; RCOG Green-top Guideline No. 76 (2025) takes 4.0 mU/L as the TSH upper limit where the lab has no pregnancy range, and antibody-positivity tips toward treatment. Repeat TFTs within 3 weeks (here, within days), get same-day antenatal thyroid advice, and if confirmed consider levothyroxine aiming for TSH 2.5 or less, rechecking every 4–6 weeks until 20 weeks, titrating with the obstetric/endocrine team. But this is barely an endocrine consultation: it is a grief-and-guilt consultation wearing a blood result. Respond to the distress first, answer the "did my thyroid kill them?" question with rigorous honesty (association is not retrospective causation; the past cannot be diagnosed; what we CAN do is act now), and dismantle the self-blame with evidence — miscarriage is common, rarely the mother’s doing, and autoimmune thyroid disease is not a failing. Recognise two prior losses as deserving assessment (RCOG Green-top Guideline No. 17, 2023, defines recurrent miscarriage as three or more losses but supports evaluation after two where clinically appropriate), not "bad luck", and walk beside her with concrete action and honest, non-false reassurance.