The Acute Effect of Physical Activity on Postprandial Blood Glucose in Pregnant Women

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.