changes during the course of pregnancy. How and why is
currently unknown, but might be related to mechanisms to
protect fetal growth. Hopkins and Cutfield hypothesized
that, during a healthy pregnancy, maternal insulin sensitivity
is regulated to achieve optimal fetal growth and is
not sensitive to modest increases in PA (9). This is corroborated
by their findings that an exercise intervention
initiated in the second half of pregnancy did not have an
effect on insulin sensitivity or GDM risk (10). However,
more data on longitudinal changes of PA in relation to
glucose metabolism are needed to test this hypothesis. Furthermore,
it needs to be determined whether this lack of
effect of PA is also seen in obese women, who are more
likely to have low insulin sensitivity at the beginning of
pregnancy.