Threatened Premature Labor, Antepartum

This study through to the pregnant woman blood concentrations of dexamethasone therapy after research, explore the pharmacokinetic data of dexamethasone in pregnant women, Chinese pregnant women dexamethasone pharmacokinetic model, provide a reference for the clinical use of dexamethasone dose, through the biomarkers of dexamethasone to promote fetal lung maturity and other metabolomics, It provides the basis for the effectiveness and safety study of dexamethasone.