Clinical trials

Gestational diabetes mellitus (GDM) is the most common complication and metabolic disorder during pregnancy, with clear risks to both the mother and fetus. In recent years, the long-term chronic diseases and poor prognosis in GDM women after delivery, as well as the risk of obesity and metabolic disorders in their offspring, have become key research topics. However, due to the long duration of GDM's impact on both the mother and offspring and its involvement in multiple disciplines, high-quality cohort studies are scarce. As a result, there is no definitive conclusion regarding the high-risk factors, natural progression, key mediators, timing of interventions, and targets for GDM's long-term effects on mothers and their offspring. This project intends to initiate a prospective follow-up study, establish a specialized cohort for the long-term effects of GDM on both mothers and their offspring, and complete the characterization of the natural course of non-communicable chronic diseases (NCDs) in GDM women and their offspring. The study will also explore high-risk and mediator factors, and develop predictive models. The goal is to provide education, postpartum follow-up, monitoring, and possibly initiate primary prevention for GDM women to reduce the long-term NCD risks, ultimately improving their life expectancy and providing a theoretical basis for intervention. Inclusion Criteria: 1. Adult patients (≥18 years old) who registered for antenatal care and delivered at Peking University Firest Hospital's obstetrics department between 2007 and 2016. 2. Diagnosed with gestational diabetes mellitus (GDM) during pregnancy via an oral glucose tolerance test (OGTT). 3. Signed informed consent. Exclusion Criteria: 1. Lack of pregnancy-related obstetric follow-up records. 2. Inability to cooperate with and complete subsequent scheduled follow-ups.

The goal of this clinical trial is to learn if levothyroxine (L-T4) works to treat pregnant women with TSH 2.5 mIU/L-the upper limit of reference range (ULRR) of pregnancy and TPOAb-negative. It will also learn about the safety of L-T4. The main quesitons the investigator want to answer are: * Will L-T4 reduce miscarriage rates and have an impact on pregnancy complications in pregnant participants? * What medical issues do participants have when taking L-T4 during pregnancy? -Investigators will compare L-T4 with placebo (a substance with a similar appearance without medication) to see if L-T4 could reduce miscarriage rates Participants should: * Take L-T4 or placebo during the whole pregnancy. * Visit the hospital once every 6-8 weeks during pregnancy for checkups and tests * Keep a diary of their pregncny complications and daily record of L-T4 or placebo intake. * Visit the hospital for examination 42 days postpartum for checkups and follow up by phone at 6 and 12 months postpartum.