Effect of Probiotics on Insulin Sensitivity in Overweight and Obese Pregnancy

The goal of this clinical trial is to learn if taking a probiotic supplement during pregnancy improves the body's response to insulin (insulin sensitivity) in pregnant women who were overweight or obese before pregnancy (body mass index ≥25 kg/m2). Reduced insulin sensitivity is common in these women and increases the risk of gestational diabetes mellitus and excessive fetal growth. Growing evidence suggests that the bacteria in the gut (gut microbiome) play a role in regulating blood sugar and insulin action. The main questions it aims to answer are: * Does a daily probiotic supplement improve insulin sensitivity in mid-pregnancy? * Does it affect blood sugar levels, insulin production, the development of gestational diabetes mellitus, fetal growth and the gut bacteria of mothers and newborns? Participants will: * Take one sachet of the probiotic OMNi-BiOTiC® METAtox twice daily from early pregnancy until delivery (probiotic group only) * Attend three study visits in early, mid and late pregnancy with blood tests, an oral glucose tolerance test (early and mid pregnancy), measurements of weight and blood pressure, and questionnaires on diet and physical activity * Wear a glucose sensor on the upper arm for 10 days after each visit * Provide stool samples at each visit and a first stool sample of their newborn * Have fetal growth checked by ultrasound and pregnancy and birth outcomes recorded

Inclusion Criteria: * Pregnant women aged 18 to 50 years * Gestational age 12+0 to 15+6 at inclusion * Preconceptional body mass index ≥25 kg/m2 * Written informed consent Exclusion Criteria: * Any acute illness within 2 weeks prior to the study * Preconceptional diabetes (type 1, type 2 or others) * Preconceptional endocrine disorder (Cushing Syndrome, M. Addison) * Status post bariatric surgery * HIV or hepatitis infection * Severe liver or kidney dysfunction * Current malignant tumors * Participation in another interventional study