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Assisted Reproduction and Infertility
Obesity, Polycystic Ovary Syndrome and Fertility
Pier Giorgio Crosignani
Professor of Obstetrics and Gynaecology, and Consultant, Research Programmes on Lifestyle and Women’s Health,
Fondazione IRCCS Policlinico, University of Milan
Abstract
Obesity is a common public health burden. Around 30–40% of pre-menopausal obese women present to their clinician with polycystic
ovary syndrome (PCOS), while 40–60% of women with PCOS are overweight. Both obesity and PCOS have detrimental effects on natural
fecundity. In addition, obesity reduces the success rate of all pro-fertility treatments and increases the risks associated with pregnancy,
both for the mother and for the foetus. Restoring health and fertility with diet seems the most obvious and effective programme for
overweight women.
Keywords
Overweight, obesity, polycystic ovary, fertility, pregnancy complications, diet, fecundability
Disclosure: The authors have no conflcts of interest to declare.
Received: 19 December 2008 Accepted: 9 February 2009
Correspondence: Pier Giorgio Crosignani, Fondazione IRCCS Policlinico, Via M Fanti, 6, 20122 Milan, Italy. E: piergiorgio.crosignani@unimi.it
Obesity and Polycystic Ovary Syndrome – syndrome (PCOS), which is present in 20–25% of women of fertile
Two Frequent Conditions age.
7
PCOS is by far the most common endocrine disease and is
Obesity found in 5–10% of normal young subjects, with its highest
Until a few years ago, obesity was defined as a body mass index prevalence (80–90%) being observed in patients with acne and/
(BMI) ≥27kg/m
2
.
1
In 2006, the lower limit of BMI for obesity was or hirsutism.
8
increased to 30kg/m
2
. The condition is now common everywhere,
and the only world region in which obesity is not common is Deleterious Synergism Between Excess Fat and
Sub-Saharian Africa. Elsewhere, obesity is linked to poverty and is Polycystic Ovary Syndrome
much more common in females.
2
Today, the public health burden Around 30–40% of pre-menopausal obese women present to
caused by obesity resembles that of smoking, which was previously clinicians with polycystic ovary syndrome, while 40–60% of women
the most common cause of preventable death.
3
In Denmark, the with PCOS are overweight.
9
The frequent association between the
prevalence of obesity in young men has doubled in the past 15 two conditions leads to detrimental synergic effects. Insulin
years.
4
In the UK a similar trend has been observed in women resistance, one of the important dysmetabolic factors of PCOS, is
booking into antenatal clinics.
5
closely related to bodyweight; therefore, unsurprisingly, BMI
appears to be one of the most reliable predictors of PCOS severity
Body fat distribution is more important than its excess, and and a good predictor of the reduced fecundity that is often found in
central obesity seems the most reliable index of the metabolic overweight women.
10
dysfunction. Bodyweight measurement cannot reliably assess
the severity of the condition because it is an imprecise Similarly, since the sex hormone imbalance (less sex hormone-
measurement of visceral adiposity. Furthermore, bodyweight binding globulin [SHBG] equates to more androgen), the other main
measurement and BMI calculation fails to detect the conversion of symptom of PCOS, is amplified when patients are overweight,
lean to fat tissue due to ageing and the proportion of fat tissue lost as expected obese PCOS patients present the most severe form
with physical exercise during dieting (see Figure 1). A better of the syndrome. It has recently been reported that in PCOS
evaluation of fat distribution can be achieved through the patients the effect of the obesity-linked gene is mediated through
calculation of waist-to-hip ratio but, unfortunately, the the excess fat.
11
measurement of abdominal circumference is a difficult and
imprecise operation. For a reliable assessment of the condition, Detrimental Effect of Obesity and
direct anthropometric measurements are strongly advocated.
6
Polycystic Ovary Syndrome on
Natural Fecundity
Polycystic Ovary Syndrome Hippocrates reported the antifertility effect of being overweight
Any combination of two of three conditions (oligo or anovulation, more than 2,000 years ago,
12
but this negative correlation was
hyperandrogenemia, polycystic ovaries) define polycystic ovary neglected for a long time. Only in the last 15 years have several
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