Methods
Design and Study Population
The methods of this study have been described in detail
previously (Text S1 and S2) [17]. The study is a cluster-randomized
trial conducted in maternity clinics of primary health care centers of
14 municipalities in Pirkanmaa region in south-western Finland. All
14 municipalities with at least 70 annual deliveries were recruited to
the study. The unit of randomization was municipality. In the
randomization process, participating municipalities were first
pairwise matched with regard to annual number of births, size
and socio-economic level of the population, estimated incidence of
GDM, and urbanity level. Municipalities were then randomized by
computer. The rationale for using cluster randomization was to
avoid contamination between trial arms, which would have
occurred if individuals or clinics were randomized. All 53 nurses
working in maternity clinics in these municipalities recruited
pregnant women at 8–12 wk gestation between 1 October 2007
and 31 December 2008. The study was completed at the end of
2009, when all participating women had given birth.
Pregnant women were eligible to enter the study if they had at
least one of the following risk factors: body mass index (BMI)
$25 kg/m2 based on measured height and self-reported prepregnancy
weight; GDM or any signs of glucose intolerance or
newborn’s macrosomia ($4,500 g) in any earlier pregnancy; type
1 or 2 diabetes in first- or second-degree relatives; or age $40 y.
Women were excluded if they had any of the following: at least
one of the three baseline (8–12 wk gestation) oral glucose tolerance
test (OGTT) measurements was abnormal (fasting blood glucose
$5.3 mmol/l, .10.0 mmol/l at 1 h, and .8.6 mmol/l at 2 h)
[1]; prepregnant type 1 or 2 diabetes; inability to speak Finnish;
age ,18 y; multiple pregnancy; physical restriction preventing
physical activity; substance abuse; treatment or clinical history for
psychiatric illness.
The research protocol was approved by the Urho Kekkosen
Kuntoinstituuttisa¨a¨tio¨ institute review board, the ethical committee
of Pirkanmaa Hospital District, and the physicians in charge of primary health care in the 14 municipalities. All participants
provided written informed consent.