Second-Trimester Thyroid Function and Pregnancy Outcome in Mothers with Hyperthyroidism

Abstract

Thyroid function at 24–28 weeks gestation was compared between 26 mothers with hyperthyroidism (16 on antithyroid treatment and 10 in remission without treatment) and 15 normal pregnant controls. There was no difference in the total and free thyroxine (TT₄ and FT₄) or in the total and free triiodothyronine (TT₃ and FT₃) concentrations, but the erythrocyte zinc (RBC Zn) concentration was significantly lower in the study group (187.3 ± 46.6 µmol/l RBC versus 223.6 ± 3.7 µmol/l RBC, p < 0.01). In the study group, both birth weight and gestation at delivery were significantly correlated with TT₃ (r = ––0.500, p < 0.02 and r = ––0.460, p < 0.05, respectively) as well as with RBC Zn (r = 0.473, p < 0.02 and r = 0.573, p < 0.01, respectively). The results suggest that plasma concentration of TT₃ and of RBC Zn at 24–28 weeks gestation may be helpful prognostic factors in the management of pregnant patients with hyperthyroidism.

Effect of maternal hyperthyroidism during late pregnancy on the risk of neonatal low birth weight

“…The comparable NBW and prevalence of LBW among infants born to ET‐1, ET‐2 and healthy control mothers observed in our study suggests that the presence of hyperthyroidism during early and mid pregnancy might not affect NBW or the risk of LBW in the infants. Our observations disagree with that of Lao et al . (1991) who reported that NBW has significantly negative correlation with plasma concentration of total T3 in mothers with hyperthyroidism between 24 and 28 weeks of pregnancy ( r = − 0·5, P < 0·02).…”