Protective Effect of Lactation Against Gestational Diabetes Mellitus in Subsequent Pregnancies: A Prospective Observational Cohort Study

Gestational diabetes mellitus (GDM) is a common metabolic disorder of pregnancy associated with increased maternal and fetal morbidity. Lactation has been suggested to improve maternal glucose metabolism, enhance insulin sensitivity, and reduce the risk of future glucose intolerance. However, evidence regarding the protective effect of lactation on the development of GDM in subsequent pregnancies remains limited. This prospective observational cohort study aims to evaluate the association between lactation and the risk of gestational diabetes mellitus and related pregnancy complications in women who conceive during the lactation period. Routine glycemic markers including fasting plasma glucose, HbA1c, glycosuria, and 75-g oral glucose tolerance test (OGTT) results will be recorded. Ultrasonographic findings including fetal abdominal circumference percentile, estimated fetal weight percentile, and amniotic fluid index will also be assessed. The study will investigate whether lactation is associated with a reduced risk of GDM, fetal macrosomia, and polyhydramnios in subsequent pregnancies.