Subclinical hypothyroidism (SCH) in pregnancy is common, according to literature, affecting up to 15% of pregnancies. It still represents a controversy weather levothyroxine has beneficial effects on pregnancy outcomes. In this retrospective and prospective cohort study, we assessed fetal and maternal outcomes in women with known thyroid status pre-pregnancy, and hypothyroidism during pregnancy. We included 393 pregnant women, 90 (22.9%) diagnosed with overt and 303 with SCH (77.1%). A total of 94 (56%) had positive anti-TPO antibodies. Levothyroxine substitution across all observational periods was suboptimal, mostly during first trimester in both groups of patients (85.4%). There was a difference in the number of live births in favor of group with SCH (p = .004). Women with overt hypothyroidism were more likely to develop complications during pregnancy (RR = 1.153, 95%CI = 0.775 - 1.714) and had positive TPO-antibodies more often (p = .022). The only significant association was found between fetal outcomes in women with SCH and positive TPO-antibodies (p = .018), while positive Tg-antibodies did not affect the pregnancy outcomes of women with SCH. Moreover, no correlation was observed between outcomes and adequacy of levothyroxine substitution. These results indicate that TPO-antibody positivity could be the most important factor of pregnancy outcomes independent of the TSH levels or adequacy of levothyroxine therapy.
Keywords: Overt hypothyroidism; TPO-antibody; Tg-antibody; levothyroxine substitution; pregnancy outcomes; subclinical hypothyroidism.