Procedures
The research staff approached pregnant women during their first prenatal consultation after the diagnosis of GDM. Women had either follow-up for their pregnancy in the hospital or were referred by their private practitioner. Eligible women were informed of the trial procedures during that first visit, in addition to information of the management of GDM. Consenting women were randomly allocated to one of the two arms. Women in both groups had the usual care provided in this multidisciplinary prenatal consultation by diabetologists, dieticians, obstetricians and midwives. Initial management included dietary advice and four times daily capillary blood glucose self-testing14. In the intervention group, an exercise program was proposed, in addition to usual care. This program included a weekly, supervised, in-hospital exercise session, at the same time the women had an appointment at the clinic for GDM management. The duration of the exercise session was 30-45 minutes and consisted of a mix of physical therapist supervised endurance effort (stationary cycling, arm-cranking) and light resistance exercise (elastic bands and free weights), personalized taking into account individual preferences and tolerance. The women warmed up for a few minutes with light load arm-cranking, followed by 10 minutes of arm-cranking targeting a heart rate >130 bpm. After a 5 minutes rest, they then engaged in exercise on a recumbent cycle-ergometer for 20 minutes, also targeting a heart rate >130 bpm. In case recumbent cycling was not bearable, this exercise was replaced by stepping exercise targeting a heart rate >130 bpm. During the training sessions the women wore a thoracic belt (Suunto Smartbelt, Vantaa, Finland) for heart rate monitoring. Session intensity was quantified by the average heart rate of the session and peak heart rate reached.
Using motivational interviewing techniques, the physical therapist coached the women to engage in more regular physical activity in daily life. They were encouraged to accumulate 5000 or more steps per day, monitored by a pedometer (HJ 112, Omron, Hoofddorp, Netherlands). Women were given diaries to record their physical activities, total number of steps per day and blood sugar levels.