"While many people recommend that weight loss in
pregnancy, particularly for very obese women is OK ... (there) may
be adverse effects," said Dr. Patrick Catalano, director of the
Center for Reproductive Health at MetroHealth in Cleveland, Ohio.
"We don't have much data, in particular on body composition changes
in overweight (or) obese women who lose weight," said Catalano, who
led the new study. "Maybe we need to be a little bit more careful
before we are just glib about saying it's OK."
Research has offered evidence of many risks posed by obesity to
mother and fetus during pregnancy, up to and beyond the point of
Obese mothers are at raised risk of early spontaneous abortion and
fetal birth defects. Later on, there is a higher chance of
gestational diabetes and preeclampsia. At delivery, obese mothers
are more likely to need a cesarean-section and to have postpartum
The newborns of obese mothers are at risk of being overly large for
their gestational age and that has been tied to childhood obesity.
The U.S. Institute of Medicine (IOM) issued guidelines in 2009
recommending that obese women gain between 5 and 9 kilograms (11 to
20 pounds) during pregnancy, which is somewhat less than the gain
recommended for women who start pregnancy at a normal weight.
However, some researchers have suggested that for obese women,
little to no weight gain, and even weight loss, is preferable during
pregnancy to minimize the risks associated with obesity.
The American Congress of Obstetricians and Gynecologists recommends
that individualized care be given to overweight or obese women who
wish to gain less weight than recommended by the IOM.
Yet, little is known about the fetal health risks associated with
weight loss or limited weight gain by overweight or obese women
To investigate, Catalano, who was involved in developing the 2009
IOM guidelines, and his co-authors examined the effects of any
weight loss or a weight gain of less than IOM's minimum 5 kg
They looked at 1,241 full-term singleton pregnancies among
overweight and obese women.
Most (85 percent) of the women gained more than the IOM's minimum 5
kg during pregnancy, averaging a gain of 14.4 kg (32 lbs).
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In contrast, 15 percent of the study participants had weight
gains below IOM's minimum, averaging a gain of just 1.1 kg (2.4
pounds) while pregnant.
Infants born to women who gained little or no weight during
pregnancy tended to be small for their gestational age, and had less
lean body mass and less fat mass than infants born to women who
gained more than 5 kg, Catalano and his team report in the American
Journal of Obstetrics and Gynecology.
These infants also had a lower percentage of body fat, a smaller
head circumference, lower birth weight and were smaller in length
than infants born to women who gained more than 5 kg during
The results held when the authors took into account the mothers'
pre-pregnancy weight, smoking status, glucose tolerance (a measure
of pre-diabetes or diabetes) and other factors that may have
influenced the infants' development.
Infants born to 46 women who lost weight during pregnancy were also
small for their gestational age and had decreased lean and fat mass,
lower birth weight and a lower percentage of body fat.
In contrast, infants born to women who gained more than the IOM
minimum were more likely to be large for their gestational age.
Among infants born to women who gained more than 5 kg, 13 percent
were large for their gestational age. In comparison, 7.5 percent of
infants born to women who gained 5 kg or less were large.
"Everyone agrees having a very big baby is not good," Catalano said.
However, "the loss of lean mass may have long-term consequences" as
well, he said.
What's the bottom line for obese and overweight women? "Lose weight
between pregnancies," Catalano recommends. "We just don't know if
it's safe to do during pregnancy."
Journal of Obstetrics and Gynecology, online Feb. 11, 2014.
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