The aim of the project is to investigate the acute effect of exercise on blood glucose after food consumption. Thereby the investigators wish to achieve knowledge that can improve prevention and treatment of gestational overweight and gestational diabetes mellitus (GDM). This will prevent serious complications during pregnancy and birth, but also long term complications like type 2 diabetes mellitus (T2DM) for both the mother and the offspring.

Inclusion will be 60 pregnant women divided into three groups - normal weight, overweight and obese and women with gestational diabetes. Participants will receive a fixed diet and go through an intervention period with physical activity immediately after each main meal and a control period with inactivity after the meals. Blood glucose will be the main outcome.

Design: Crossover controlled study. Cases: 60 pregnant women recruited at the Department of Obstetrics and Gynecology, Aarhus University Hospital (AUH). Subjects will receive both written and oral information before entering the trial. According to their prepregnancy BMI, subjects will be recruited for three different groups: i) normal weight (BMI 18,5-24,9), ii) overweight and obese (BMI ≥ 25) and iii) GDM. 20 women in each group. Group i and ii will be recruited at the routine ultrasound scan at gestational week 19. Group iii will be recruited after the Oral Glucose Tolerance Test (OGTT) that diagnoses gestational diabetes mellitus. The routine OGTT is done at gestational week 28. When diagnosed with GDM the women are referred to Department of Obstetrics and Gynecology, AUH, and the investigators will recruit participants from here. Participants will be examined during gestational week 30-34 where insulin resistance peaks during pregnancy.

Intervention: Participants will receive a fixed diet for a total of 8 days. The 8 days of fixed diet are split into a 4 days intervention period and a 4 days control period separated by two days of regular food intake. The two days of regular food intake will function as a "wash out period" to avoid carry over effect. During the 4 days intervention period the participants will perform 30 minutes of interval walking immediately after each main meal. The interval walking consists of alternating fast and slow intervals (3 minutes each) aiming at > 70% and < 40% of peak energy expenditure measured by the Sensewear Armband. During the 4 days control period the participants will be normally active, not performing any set physical activity. Participants will be randomized to the order of the two periods.

Study variables: Fasting blood samples will be taken on the first day of both the intervention and control period and on the morning after the last day of each period. Blood samples will be analyzed for blood glucose, HbA1c, C-peptide and lipid profile (triglycerides, HDL and LDL).

During the entire experimental period, movement data will be collected using the Sensewear Armband. Blood glucose will be monitored continuously using the IPro2 Continuous Glucose Monitor (CGM) from Medtronic.

The diet will consist of three main meals and three snacks and will be calculated to match their metabolic need. The calculations will be done by a nutrition specialist and will include weight, height, BMI and energy need during 3rd trimester pregnancy.

Data on demography, family history of diabetes, prepregnancy BMI, gestational weight gain and complications during pregnancy are collected from medical records of the patients and their offspring.

Inclusion Criteria:

• Pregnant women over age of 18
• according to each group: BMI: 18,5-24,9; BMI: >25; women with GDM.

Exclusion Criteria:

• women with a physical disability that affects their movement will be excluded from the study