Accounting for a 30% drop off, a total enrolment of 150 patients is planned. Patients will be randomized at time 0 (10°± 2 weeks of gestation). Follow-up visits will take place at weeks 14 ± 2, 24 ± 2, 32 ± 2, 36 ± 2 weeks, and between months 3° and 6° after labour. An optional visit could be done 12 months after labor. Plasma and serum monitoring of thyroid hormones, Tgab, TPOab, Se concentration, Selenoproteins and cytokines, thyroid US, SF12 questionnaire will be made at all the follow-up visits. At visit 3 (24 ± 2 weeks) patients will optionally do the OGTT). Gestational, obstetrical, maternal, fetal, and infant anamnestic data will be taken, during the follow up visits and at labour.