Women who gain as little as 7 pounds between
pregnancies can put themselves and their babies
at medical risk, even if they don't become
overweight, suggests a provocative study of
thousands of women.
Researchers found that gaining weight during
that interval — not during the pregnancy
itself — raised the risk of such complications
as diabetes and high blood pressure during
the second pregnancy, and even stillbirth.
Pregnant women with diabetes or high blood
pressure are at risk of convulsions or organ
damage, which in severe cases, can be fatal.
The results provide new evidence that overweight
or obese women who plan to become pregnant
should lose weight, and that women with healthy
weights should avoid packing on pounds before
pregnancy, the researchers said.
The work was reported Thursday in the British
medical journal, The Lancet, by Drs. Eduardo
Villamor of the Harvard School of Public Health
and Sven Cnattingius of the Karolinska Institute
in Sweden. They examined records of more than
150,000 Swedish women who delivered two children
between 1992 and 2001.
The researchers focused on body-mass index,
or BMI, a calculation from a person's height
and weight. They examined the difference between
the women's BMI at the beginning of two consecutive
pregnancies. And they examined the likelihood
of complications such as high blood pressure,
diabetes, the probability of a Caesarean delivery,
and stillbirth in the second pregnancy.
One striking finding was that the risk of
complications rose even in women who did not
end up overweight, Villamor said Thursday.
For instance, the authors offered the example
of a 5-foot-5 woman who weighs 139 pounds
before her first pregnancy. That would give
her a healthy BMI of 23.
If she gained just 7 pounds before her second
pregnancy, she'd move her BMI up a notch to
24, still considered healthy. But the new
study suggests she would also raise her risk
of becoming diabetic during the second pregnancy
by about 30 percent.
If she gained 13 pounds, raising her BMI
by 2 units and making her overweight, her
diabetes risk would double.
"Those are staggering numbers," said Dr.
Daniel Herron, associate professor of surgery
at Mount Sinai Hospital in New York, who was
not connected to the study.
"There's long been a perception that being
morbidly obese is associated with diabetes,
but we may now be seeing this with relatively
small weight increases too," he said. "That's
news."
Overall, the new study says gaining 1 or
2 BMI units increases the risk of diabetes
and high blood pressure during pregnancy by
up to 40 percent. Gaining 3 or more units
raised the risk of a stillbirth by 63 percent.
"The results from this study are definitely
provocative," said Dr. Mario Merialdi, a reproductive
health specialist at the
World Health Organization, who had
no ties to the study.
"It is the first study to lend support to
a causal relationship between obesity and
adverse outcomes," he said, adding that while
previous studies have been suggestive, none
has provided the necessary evidence to show
a link.
Villamor said he believed the Swedish study
would apply to other, more diverse populations,
although he said it's important to confirm
that.
Herron agreed: "I think that it does hold
a lot of importance for American women as
well."
In an accompanying commentary in The Lancet,
Aaron Caughey of the University of California
in San Francisco, writes that "as with any
groundbreaking study, these findings raise
several questions that cannot be answered
by the data alone." One of the study's limitations
is that it could not address the reasons for
weight gain, which may in turn be associated
with some of the identified health problems.
Breastfeeding practices, Caughey suggests,
might explain why some women gained weight
between pregnancies and others didn't. Women
who breastfeed typically lose more weight
than those who don't.
Addressing this issue could allow doctors
to spot women at risk of becoming obese between
pregnancies. Further studies, including those
with weight-loss interventions, experts say,
are necessary to confirm a definitive link
between obesity and pregnancy complications.
But Herron said women should not wait for
later research before changing their behavior
between pregnancies.
"For anyone who's ever thought that gaining
or losing 7 pounds didn't make a difference,
this should make them think twice," he said.
