Effect of Levothyroxine Treatment on Pregnancy Outcomes and Offspring Development in Women with Subclinical Hypothyroidism and Assisted Conception

Abstract

Objective: To investigate the effects of levothyroxine (LT4) replacement therapy on pregnancy outcomes and offspring development in pregnant women with subclinical hypothyroidism (SCH). Methods: This prospective randomized study included 128 pregnant patients with SCH who underwent assisted conception at our hospital. Patients were randomly allocated via a random number table to either the intervention group (n = 64, basic treatment plus LT4 replacement therapy) or control group (n = 64, basic treatment only). Thyroid function hormone index scores, pregnancy outcomes, and growth and development of newborns were compared between the two groups. This study complied with all relevant clinical trial safety and medical ethics guidelines. Results: In early pregnancy, there were no statistically significant differences in serum thyroid stimulating hormone (TSH), free triiodothyronine (FT3), serum free thyroxine (FT4), and total triiodothyronine (TT3) levels between the intervention and control groups (p > 0.05). In mid- and late pregnancy, the serum TSH levels of pregnant women in both groups were significantly lower than those during early pregnancy; however, the intervention group exhibited a significantly greater decrease compared to the control group (p < 0.05). While FT3 and FT4 levels were not significantly different between the two groups during mid- and late pregnancy (p > 0.05), TT3 levels were significantly higher in the intervention group in mid-trimester (p < 0.05). Offspring weight was significantly greater than that in the control group at 1 and 7 months after birth (p < 0.05), while offspring length was significantly greater in the intervention group at birth and 1 month after birth (p < 0.05). The rate of adverse pregnancy outcomes was significantly lower in the intervention group (18.75%) compared to the control group (34.38%) (p < 0.05). The intellectual and motor development scores of infants at 12 months after birth were significantly higher in the intervention group than those in the control group (p < 0.05). Conclusion: Basic treatment combined with LT4 replacement therapy can effectively improve thyroid hormone levels in pregnant women with SCH, promote early fetal and neonatal development, and reduce adverse pregnancy outcomes. Nevertheless, due to the single-center design of this study, as well as the limited sample size, further studies are required to confirm our results.