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Polycystic Ovary Syndrome
Figure 1: Birth Rate by Body Mass Index
to achieve ovulation positively correlated with bodyweight.
26
Recently, a
large randomized controlled trial showed that the live birth rate in obese
women (BMI ≥30) with PCOS was significantly lower than in women with
1
a BMI <30, irrespective of the type of oral treatment (p<0.001) (see
Figure 1).
27
0.8
A higher cancellation rate with gonadotropins associated with an overall
0.6
BMI <30
lower cumulative pregnancy rate has also been reported in obese PCOS
women.
28,29
These studies highlight the impaired response to
0.4
pharmacotherapy in obese versus lean PCOS women. Those women with
Rate of live birth
BMI 30–34
BMI a favorable response to pharmacotherapy, however, are linked to an≥35
0.2 increased risk of multiple gestation and hyperstimulation.
p<0.001
0 Effect of Weight Loss in Women with Polycystic
0 150 200 250 300 350 400 450 500
Ovary Syndrome
Days from randomization to live birth
Although the mechanisms by which obesity interferes with the
pathophysiology and clinical expression of PCOS are complex, the
Source: Legro et al., 2007.
27
Reprinted with permission. Copyright © 2007 Massachusetts
referenced data suggest that weight loss may offer a cheap and safe way
Medical Society. All rights reserved.
to improve the metabolic and reproductive profiles of obese women with
Links Between Obesity and Reproductive Outcomes PCOS.
Obesity in women is characterized by similar comorbidities as in men:
increased risk of diabetes, heart disease, gall bladder disease, A number of studies have demonstrated that a 5–10% reduction in
osteoporosis, and certain cancers, including breast and uterine. bodyweight may be sufficient to improve endocrine function, ovulation,
and, possibly, pregnancy rates in women with PCOS.
30–32
Interestingly,
Recently, in a study of more than 7,000 women, fecundity was found to 5–10% weight loss is associated with a visceral adipose tissue loss of
be significantly reduced in obese women (odds ratio (OR) 0.82, 95%
confidence interval (CI) 0.72–0.95) compared with normal-weight
women, and was even more evident in obese primiparous women (OR
0.66, 95% CI 0.49–0.89).
20
Interestingly, these findings persisted even in Weight loss may offer a cheap and safe
women with regular menstrual cycles. In a large British study examining
way to improve the metabolic and
5,799 females, both obesity at age 23 years and obesity at age seven
years independently increased the risk of menstrual problems by age 33 reproductive profiles of obese women
years (OR 1.75 and 1.59, respectively).
with polycystic ovary syndrome.
Consistent with these findings, obese women at 23 years were less likely
to conceive within 12 months of unprotected intercourse (relative risk
(RR) 0.69).
21
It is clear that obese women are at a higher risk for infertility, around 30%.
33
However, not all women who lose weight exhibit
but the underlying mechanisms are unclear. It could be an ovulatory resumption of menses; predictors of a favorable response to weight loss
problem, as women with central obesity have associated need to be identified.
hyperinsulinemia, low SHBG levels, and concomitant hyperandrogenism.
This condition has been called ‘relative functional hyperandrogenism.’
22
There are only a few studies in the literature that have examined
the independent effects of weight loss in women with PCOS, and
The presence of ovulatory dysfunction is further supported by the the majority of these are limited by small size, varied duration of
studies describing increased IVF cancellation rates, decreased numbers treatment, absence of a control group, and use of menstrual frequency
of oocytes retrieved, decreased clinical pregnancy rates,
23
and instead of pregnancy rates as a reproductive end-point. These studies
increased number of miscarriages in obese compared with normal- are discussed in detail depending on the duration of the
weight women.
24,25
lifestyle modifications.
Links Between Obesity and Reduced Fertility in Short-term Lifestyle Modification in Women with
Women with Polycystic Ovary Syndrome Polycystic Ovary Syndrome
Early onset of obesity—such as in adolescence—is associated with Two studies have examined the effects of hypocaloric diets over a four-
irregular menses and anovulation. Whether this link results in to 16-week period.
34,35
No difference in weight loss was found between
predisposition to the development of PCOS is unclear. From the studies high- versus low-protein dietary composition in either study. In the
so far described, it can be hypothesized that obese women with PCOS Moran study, 14 women were randomized to each group and weight loss
have impaired fertility compared with lean women. A prospective study was associated with resumption of menstrual function (~50%) in both
of 158 anovulatory women found that the dose of clomiphene required groups, with a better response in women with hyperinsulinemia. Longer-
10 FERTILITY TREATMENT REVIEW
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