Demographic and weight-history information was obtained at
study entry. The primary endpoints were the proportion of women
with an excessive gestational weight gain on the basis of the 1990
IOM guidelines and the proportion of women at (60.9 kg) or
below their pregravid weights at 6 mo postpartum. The 1990
IOM guidelines were used because these data were collected
before the 2009 revisions. Pregravid weight was based on a selfreport
at the time of study enrollment. Although the validity of
self-reported prepregnancy weight has been shown to be good,
especially if collected early in pregnancy (18, 32, 33), a measured
weight from the year before pregnancy was available from
the clinical records of 203 of the 401 participants (109 NW and
94 OW/OB women) to assess the validity of recalled prepregnancy
weights. The correlation between the participant selfreported
and physician measured weights was 0.95 (P = 0.0001)
with a mean discrepancy of 0.5 6 3.0 kg and no significant (P =
0.64) differences between NWand OW/OB subjects. These data
provided evidence that participants’ self-reported weight information
was a valid indication of their prepregnancy weight,
even across weight strata. Heights were measured by trained
research staff with a stadiometer at study entry. Total gestational
weight gain was computed on the basis of the pregravid weight
and weight at the last clinic visit (on calibrated scales) before
delivery. On the basis of the 1990 IOM guidelines (21), we
classified gestational weight gain as excessive in NW women
whose weight gains were .35 lb (15.9 kg) and in overweight
women whose gains were .25 lb (11.4 kg). Because the 1990
IOM recommendation for obese women provided only a lower
limit of gain, similar to other studies, we combined overweight
and obese women in our analysis and set the upper weight gain
goal of 25 lb (11.4 kg) (34–36). Postpartum weight, changes in
demographics, and breastfeeding status (any breastfeeding
compared with formula only) were obtained by a blinded research
assistant at the 6-mo postpartum visit. Obstetric records
were abstracted after delivery to obtain maternal and fetal
complications.