LIGHT Trial: Levothyroxine for Gestational Hypothyroidism in Recurrent Pregnancy Loss

The goal of this randomized, double-blind, placebo-controlled clinical trial is to evaluate whether levothyroxine supplement improves pregnancy outcomes in women with recurrent pregnancy loss (RPL) and isolated maternal hypothyroidism (IMH). The main questions it aims to answer are: Does levothyroxine increase the live birth rate after 24 weeks of gestation? Does levothyroxine improve secondary outcomes such as ongoing pregnancy rates, reduce the incidence of pregnancy loss, or influence maternal and neonatal complications? Researchers will: Compare the levothyroxine treatment group (50 µg/day) to the placebo group to assess the impact of the intervention on live birth rates and other pregnancy outcomes. Participants will: Be randomly assigned to receive either levothyroxine or a placebo. Take the assigned treatment daily starting from enrollment until the end of pregnancy. Undergo routine follow-up visits to monitor pregnancy progress and outcomes. This trial seeks to determine whether routine levothyroxine supplementation can improve pregnancy outcomes for women with RPL and IMH.

Investigators will perform a multi-center, randomized, placebo, double-blind clinical trial of levothyroxine (LT4) in patients aged between 18 years and 40 yearls who are diagnosed with isolated hypothyroxemia (defined as lower FT4 level with normal TSH) and have a previous history of recurrent miscarriages (defined as two or more pregnancy loss). Investigators will assess the effects of standard dose of 50ug/d levothyroxine therapy from the day after randomization to the day of delivery on the pregnancy outcomes, including live birth, neonatal complications, and adverse pregnancy outcomes, etc.