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Weight loss to improve fertility outcomes: how far should we go?

14 April 2014
Appeared in BioNews 750

Obesity is now a pandemic and undoubtedly the greatest burden facing health services worldwide. Twenty percent of women of childbearing age are thought to be obese. It is well-established that, in women, obesity is associated with reduced rates of ovulation, increased miscarriage rates and poor response to ovarian stimulation during assisted conception. Male fertility also appears to be similarly adversely affected with evidence of a reduced ejaculate volume, reduced sperm count and increased sperm DNA damage in obese men.

These factors result in increased time to conception, and lower implantation and pregnancy rates following both spontaneous and assisted conception in those couples where either the female or male partner or both are obese. Fertility problems therefore remain a key issue for many obese and overweight individuals: a problem compounded by the fact that most clinical commissioning groups restrict NHS funding of IVF to those couples where the female partner has a body mass index (BMI) of 30 or less.

There is little doubt that weight loss improves both fertility and reproductive outcomes. Reductions in BMI are associated with a return of ovulatory cycles, improved sperm counts, improved conception rates for both spontaneous and assisted conception, and improvements in outcomes for mothers and their babies – not to mention the long term health benefits associated with weight loss.

Traditionally, lifestyle interventions have been the mainstay of pre-conceptual weight loss for those with difficulties conceiving, comprising calorie restriction with increased exercise, often as part of a weight management programme. However, lifestyle interventions have been shown to be largely ineffective in achieving and sustaining significant weight loss. As a result, patients and healthcare professionals alike are turning to more novel methods of weight management including weight loss medications and weight loss surgery.

Weight loss surgery comprises procedures that restrict stomach capacity, for examplevia compression using an adjustable band (laparoscopic adjustable banding) or bypass part of the stomach and absorptive parts of the small bowel (gastric bypass). These procedures have proved effective in achieving and sustaining weight loss. Numbers of surgical weight loss procedures performed in the UK have risen dramatically over recent years.

Currently, women of reproductive age account for just under half of those undergoing weight loss surgery. At present, NICE recommend weight loss surgery for those with a BMI over 40 and those with a BMI over 35 with over associated medical conditions – could and should ovulatory subfertility be considered an associated medical condition?

The evidence surrounding fertility and pregnancy outcomes following weight loss surgery is growing. It appears that the resulting weight loss can restore the balance of reproductive hormones, restore ovulation and increase spontaneous conception rates and that there may be an associated reduction in miscarriage rates. Reductions in gestational weight gain have been seen in pregnancies following gastric banding, with associated improvements in maternal outcomes, with reductions in blood pressure problems in pregnancy including pre-eclampsia and lower rates of diabetes in pregnancy.

Concerns have been raised regarding the potential impact of nutritional restriction on the growing fetus, but this has not been a consistent finding and the vast majority of studies allayed concerns. What also remains unclear is how the gastric band should be managed in pregnancy, although results are soon to be expected on a national cohort study which should provide answers to this question.

Traditionally, women have been advised to delay conception for a year following bariatric surgery because of concerns over the effect dramatic weight loss may have on a developing pregnancy, however recent data from our group and others suggests that conception prior to one year following surgery may be safe, which may be preferential for those who have previously struggled to conceive or are undergoing assisted conception. Of course, bariatric surgery itself may negate the need for assisted conception, allowing patients to achieve their goal of conception and resulting potentially in short and long term cost savings for the health service in terms of provision of fertility services and provision of long term medical care for these patients.

Of course, weight loss surgery is not without its potential risks and complications and should only be considered once conservative lifestyle measures have failed. But it would seem, for those in whom lifestyle measures fail, weight loss surgery may be a credible treatment option for those with obesity-associated subfertility. This will require a shift in thinking and an open mind from patients and clinicians alike.

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