The heavier a woman is, the greater the risks to her
newborn, researchers found.
“Maternal obesity is associated with a number of complications
during pregnancy and delivery, but the underlying mechanism is not
fully understood,” said Dr. Marie Blomberg of Linkoping University
in Sweden. She was not involved in the new study.
To learn more, researchers analyzed data from a medical register of
all live singleton, term births between 1992 and 2010 in Sweden,
which included more than 1.7 million babies.
The register had information on women’s height and weight early in
pregnancy, as well as babies’ medical problems and so-called Apgar
The Apgar score assesses vitality using measures of heart rate,
breathing, muscle tone, skin color and activity on a scale from zero
to 10. There can be many reasons for a low Apgar score, but the most
common reason is lack of oxygen, lead author Dr. Martina Persson
told Reuters Health in an email.
Persson worked on the study at the Karolinska Institutet in
Less than one in 1,000 babies had an Apgar score between zero and 3
at five minutes after birth, and even fewer had that low a score at
10 minutes after birth.
Compared to babies of normal-weight mothers, babies with overweight
mothers were 32 percent more likely to have an Apgar score that low
at 10 minutes.
Babies of obese mothers were 57 percent more likely to have a low
Apgar score, and those of severely obese mothers were 80 percent
A newborn’s risk of seizures also increased with maternal weight.
For instance, babies of severely obese mothers were twice as likely
to have a seizure as those of mothers with a healthy weight.
The increased risks were similar for meconium aspiration, which
happens when the baby releases stool in the womb and inhales the
stool-tainted amniotic fluid.
“Meconium release is a sign of fetal stress,” Persson said.
“Meconium aspiration may give severe breathing problems in the
newborn and is associated with birth asphyxia and low Apgar scores.”
“Meconium aspiration and seizures could be serious in the immediate
newborn period although still the majority of these children will be
healthy,” Blomberg told Reuters Health in an email.
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Researchers don’t know why these risks, which all relate to lack of
oxygen, go up for babies of overweight and obese women, Persson
Obesity in pregnant women has been associated with metabolic changes
and inflammation, which could affect the placenta and fetal
environment in a way that leads to low oxygen levels and more fetal
growth, she noted.
Also, larger babies, often born to larger mothers, may be more
likely to experience trauma during delivery, which could result in
lack of oxygen, she said.
“One must bear in mind that even though these conditions are
potentially very dangerous for the baby, the absolute risks for the
studied outcomes are low,” Persson said.
Even with the most obese mothers, the risk of infants having a low
Apgar score at five minutes was still only 0.24 percent, or less
than three babies out of every 1,000.
In addition to encouraging prospective mothers to strive for a
healthy weight, doctors can closely monitor babies during labor and
delivery, which likely reduces the risk of lack of oxygen at birth,
“Enjoy your pregnancy!” Persson said. “Try to eat healthy and be
physically active. Seek support from your midwife in order to change
bad eating habits and try not to gain too much weight during
PLOS Medicine, online May 20, 2014.
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