Our results showed that weight gain in pregnancy was
lower when pre-pregnancy BMI was higher. In particular,
women who were overweight or obese before pregnancy
generally gained less weight during pregnancy and very
few had an excessive weight gain. Conversely, only 2 of
the 161 lean women had a low weight gain. This rela-
tionship has been well established [
14
–
20
] but the reason
for this is not obvious. It can be speculated that medical
management and/or personal efforts for not gaining too
much weight could be responsible for a part of this asso-
ciation. However, during pregnancy, fat is stored to secure
energy supply during fetal growth and lactation. In obese
women, no additional storage is necessary, which suggests
that pregnancy weight gain could be restricted because of
physiological mechanisms.
Our study was based on self-reported measures of
weight before pregnancy whereas many studies have found
that weight is more likely to be under-reported by women
with a high pre-pregnancy BMI [
24
]. Such a bias would
therefore impact on the calculation of gestational weight
gain and lead to an over-estimation of weight gain in
overweight and obese women. We performed a sensitivity
analysis and used weight measured at booking instead of
recalled weight for the calculation of gestational weight
gain and BMI. Gestational weight gain was divided by the
number of remaining weeks of gestation, and then