Table 2.

Management of thyroid dysfunction during spontaneous conception, ART treatment and pregnancy, according to the latest guidelines

Hyperthyroidism and pregnancy	- In case of hyperthyroidism (increased fT3 and/or fT4), pregnancy (both spontaneous pregnancy and ART treatment) should be planned after normalization of thyroid function -If TSH < 0.3 but normal fT3/fT4, ART may not be postponed -Propylthiouracil is the preferred drug in the first 16 weeks -fT4 levels should be kept in the upper third of the normal non-pregnant reference range, without aiming at TSH normalization
Hypothyroidism, thyroid autoimmunity and pregnancy		ART procedures	Spontaneous pregnancy
	Should be treated	-All women with overt hypothyroidism -All women with TSH > 4.0 mIU/L	-All women with overt hypothyroidism -All women with TSH > 10 mIU/L -TPOAb+ women with TSH RR–10 mIU/L
	May be treated	-TPOAb+ women with TSH 2.5–4 mIU/L -TPOAb− women with TSH > 2.5 mIU/L and US TAI	-TPOAb+ women with TSH 2.5–RR mIU/L -TPOAb− women with TSH RR–10 mIU/L
	Should not be treated	-TPOAb− women with a TSH 2.5–4 and no US TAI -All women with a TSH < 2.5 -Isolated hypothyroxinemia	-TPOAb− women with a TSH < RR -All women with a TSH < 2.5 -Isolated hypothyroxinemia
Follow-up during pregnancy	- In euthyroid TPO/TgAb+ women TSH concentration should be performed at the time of pregnancy confirmation and every 4 weeks through mid-pregnancy, and at least once near 30 weeks gestation - In women on LT4 treatment undergoing COH, both TAI+/TAI, TSH should be evaluated the day of the confirmatory hCG measurement

ART assisted reproductive technique, TSH thyroid-stimulating hormone, US TAI ultrasonographic evidence of thyroid autoimmunity, RR (pregnancy- and population-specific) reference range, TPOAb+ thyroid peroxidase antibodies positive, TgAb+ thyroglobulin antibodies positive, TPOAb− thyroid peroxidase antibodies negative, TgAb− thyroglobulin antibodies negative, COH controlled ovarian stimulation