The purpose of this study is to assess the feasibility of randomizing pregnant women at high risk for gestational diabetes to a 24-week period of soy food consumption. This study will also examine the effects of soy protein and isoflavones on glucose metabolism and lipid levels among pregnant women at high risk for gestational diabetes, and on child's weight and height at birth and 6 weeks of life.

Evidence from animal studies, human observational studies, and some randomized controlled trials has suggested that soy protein and isoflavones have beneficial effects on lipid and glucose metabolism. Additionally, soy isoflavones can diffuse across the placenta, enter fetal circulation and potentially reduce the susceptibility to cardiometabolic disorders in adulthood. Given the high prevalence of GDM and its serious health consequences for women and their children, and likely health benefits of soy protein and isoflavones on a panel of metabolic parameters, the role of maternal supplementation of soy protein and isoflavones for prevention of GDM and/or minimization of GDM severity in mothers and for improving health indicators in their offspring merits investigation.

This study will provide new and essential information about the efficacy and feasibility of using soy-based whole foods to prevent and manage gestational diabetes development. This study will be a randomized, placebo-controlled trial. Forty pregnant women at high risk for gestational diabetes will be recruited from the obstetrics services at the Melrose Wakefield Hospital and Tufts Medical Center, and randomized to receive soy-based foods or minimize soy intake, from the 16th gestational week to birth. To measure participants' compliance with the treatment, the study will use three methods: (1) monthly telephone interview about adherence to the treatment; (2) daily soy food intake log; and (3) serum isoflavone concentrations. To evaluate the effects of soy supplementation on GDM, the study will collect blood samples to measure glucose, insulin, HbA1c, and lipids (triglycerides, total cholesterol, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol ). The study will also measure weight and body composition of participating pregnant women and the participants' respective children's weight, length and body composition.

Inclusion Criteria:

• Age >=18 years
• ≤ 18 weeks of pregnancy
• Singleton pregnancy
• Have at least one of the risk factors for GDM, including overweight (BMI ≥ 25 kg/m2) before this pregnancy, first-degree relative with type-2 diabetes mellitus (T2DM), abnormal glucose tolerance/GDM in previous pregnancy, and/or history of macrosomia (birth weight ≥ 4,000 gram) in previous pregnancy
• Being able and willing to give written informed consent.

Exclusion Criteria:

• Allergic to soy or milk products
• Current smoker
• Preexisting diabetes outside of pregnancy or other heath conditions that could affect glucose levels
• Chronic or serious medical conditions such as hypertension, heart disease, stroke, chronic renal or hepatic disease, or malignant disease (by self-report and medical record review)
• Use of medications that could interfere with insulin secretion or insulin sensitivity
• Weight loss during this pregnancy more than 10% of pre-pregnancy body weight
• Current severe nausea and/or vomiting (by self-report).

Individual participant data (IPD) will be not shared. Data will be shared in aggregated way in publications and national conferences.