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 Programs that promote weight loss through lifestyle change, rather
than bariatric surgery or medications, are preferred and can
increase the chance of spontaneous pregnancy, the study authors
conclude in the Canadian Medical Association Journal.
"It is important that women are aware that they may jeopardize their
reproductive health if they are obese and should consider improving
their lifestyle," said senior author Dr. Jean-Patrice Baillargeon of
the University of Sherbrooke in Canada.
Infertility, which is defined as the inability to become pregnant
after 12 months of trying, affects about 15 percent of couples in
Canada, the review authors note. Infertility affects 12 percent of
women in the United States, according to the Centers for Disease
Control and Prevention.
Given that 25 percent of Canadian women of reproductive age are
overweight and another 19 percent are obese, the authors write, it's
"prudent" to determine the best ways to reduce the potential impact
on fertility.
"Evidence also shows that if a mother is obese during pregnancy, it
increases the risk of obesity and diabetes in her kids as well,"
Baillargeon, who is also president of the Canadian Society of
Endocrinology and Metabolism, said in a phone interview.
Baillargeon and colleagues reviewed research published in the last
10 years on the links between obesity, fertility, lifestyle
modifications and other obesity treatment options. They focused on
analyzing data from the 20 most relevant review articles and
original research papers.
This prior research finds that the risk of infertility increases 27
percent in women who are overweight, and 78 percent in women who are
obese. Obesity is defined as having a body mass index (BMI), a ratio
of weight to height, of 30 or higher. BMI between 25 and 29.9 is
considered overweight, and between 18.5 and 24.9 is considered a
healthy weight.
Obesity most commonly harms women's fertility through menstrual and
ovulation disorders, which include polycystic ovary syndrome, the
authors write. Overall, the chance of pregnancy drops 4 percent with
each one-point increase in BMI. Obesity also decreases the
effectiveness of fertility treatments, they note.
"Women who are obese usually need more expensive fertility
treatments as well, which can be a barrier for them," Baillargeon
said. "We want women to be aware of these factors."
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Obesity can affect the pregnancy itself, the authors point out. It's
associated with higher odds of gestational diabetes, postpartum
depression and cesarean delivery. Newborns are also more likely to
be born early and have health problems such as neural tube defects
or heart anomalies.
Several international health organizations recommend a 5 percent
decrease in body weight for obese women who want to become pregnant
or pursue fertility treatments. Past studies have found that women
with polycystic ovary syndrome, in particular, benefit from weight
loss programs because they tend to have higher central obesity and
insulin resistance that could hinder pregnancy.
"These few studies don't give solutions to all of the unanswered
questions here, but on the whole, we should take notice that obesity
actively interferes with reproduction," said Dr. Annemieke Hoek of
the University of Groningen Medical Center in the Netherlands, who
wasn't involved in the review.
"Parents, future parents, government officials and policymakers
should be aware that if the population grows fatter and fatter,
we're increasing our chances of infertility," Hoek said in a phone
interview.
Although losing weight is beneficial, women should avoid extreme
dieting immediately before and during pregnancy, said Dr. Richard
Legro, a reproductive endocrinologist at the Penn State Health
Milton S. Hershey Medical Center in Pennsylvania, who wasn't
involved in the review.
"There should be a divide between getting ready for pregnancy and
actively being pregnant," he said in a phone interview. "Women
shouldn't be dieting when their bodies need to be an energy store.
It sends mixed messages to the brain."
These mixed messages, in turn, "lead to yo-yo dieting that we want
to avoid," Legro said. "We need to focus on appropriate weight
maintenance across the pregnancy cycle."
SOURCE: https://bit.ly/2MK7nZV CMAJ, online June 18, 2018.
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