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There is an obesity epidemic. That is no longer in dispute. For the first time in the history of humankind, there is more overweight than undernourished people on earth. It is testimony, if one was required, in mankind’s pathetic record on getting things right.

In the USA, in 2006 only two states had a prevalence of obesity of less than 20%. In 22 states the prevalence was equal to or above 25% and as for Mississippi and West Virginia, the prevalence was more than 30%. If you break down the figures, the problem for adults is actually much worse with the overall obesity prevalence at 32.2%. If you include those who are merely classified as overweight, the figure shoots up to 66%. That is two third of all American adults. Yes. It is that serious.




America might be top-heavy but other countries aren’t faring that much better either. In the last 25 years in the UK, rates of obesity have quadrupled, now standing at almost 23%. Alarmingly, up to 10% of six year olds are already obese, the rate rising inexorably reaching 17% (over 1 in 6) at age 15. A true time bomb. Today, 30,000 deaths annually are due to conditions caused by obesity.


Obesity effect on Fertility

Taken as a general group, obese women do have more fertility problems than their counterparts of normal body weight. However, obese women are not a homogeneous group.


Obesity and Polycystic Ovaries

There are obese women who have Polycystic Ovarian Syndrome as the underlying primary condition. Weight, in this case, is part of the syndrome. Polycystic Ovarian Syndrome is also characterized by erratic ovulation therefore reducing the possibility of conception. There is also increased risk of miscarriage. What is significant, however, even in this sub-group, is the fact that, reducing weight actually dramatically improves ovulation rates which in turn improves the chances of successful conception.


General Obesity

Leaving Polycystic Ovaries aside, the majority of overweight or obese individuals will be so because of an imbalance between calorie intake and expenditure. When more calories are taken in via food and drink and less expended via general or specific physical activity, weight gain will result.


It is a known fact that women who are significantly overweight or obese have more difficulty conceiving naturally. Even the success rate in assisted conception is significantly lower compared to their counterparts who have weight within the ‘normal’ ideal range. Now, it is possible for anybody to scoff at the statistics by pointing out a number of obese people they know who have a sizable brood seemingly attained without difficulty. That may be so but it is important to remember that conceiving is not a team sport and every one is an individual. In the UK, women with a BMI of more than 36 would not normally be offered IVF treatment on the National Health Service, specifically because of safety concerns and efforts are concentrating on helping the woman lose weight first.


Obesity and Birth defects

A recent study by researchers from the University of Texas covering 5 years and over 15,000 women published in August 2007 revealed that obese women are more likely to have babies with birth defects. The identified defects included spina bifida, heart defects, genital and bowel abnormalities and small or missing digits, arms or legs. It is not clear yet whether this is an indirect correlation but it is a another worrying finding.


Pregnancy Issues

When an obese woman conceives successfully, she is already at some disadvantage by virtue of her weight. Excessive body weight is associated with increased risk of almost all the major pregnancy complications. These include pre-eclampsia, gestational diabetes and the likelihood of needing emergency caesarean section.  The latter means, in turn, such a woman is at increased risk of anaesthetic complications and post-delivery problems including infection and thrombosis. Moreover, the routine screening and  diagnostic imaging investigations (ultrasound scanning) are much more difficult to do  and the results are often poor with the inherent risk of missing some significant findings.


The Baby

In comparative terms, a baby born to an obese woman also fares less well. There is:

  1. Increased risk of a large baby with the attendant risk of requiring emergency caesarean section, instrumental delivery, a difficult birth and birth trauma
  2. Increased risk of requiring admission in a special care baby unit
  3. Increased risk of death soon after birth (neonatal death)
  4. Obesity is an independent risk factor for stillbirth with some studies showing that the risk is increased two-fold compared to the general average.
  5. The long-term is also less rosy. These babies are also at increased risk of obesity during their adulthood.


In an Ideal World...

It is clearly the case that maternal obesity is an adverse factor when it comes to fertility. Problems encompass the entire process from the attempt to conceive, through pregnancy and well into the post-partum period. Whilst it is true that many obese women will and do navigate the process unscathed, the risks are considerable.

Trying to lose weight before embarking on a pregnancy is a noble quest, the rewards of which are far-reaching. In fact, well beyond a successful delivery of a healthy baby. Of course it is not easy but few truly good things in life are.



Last update: January 29, 2011



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Obesity and Fertility


Obesity may be an image issue but it can also be a serious reproductive health challenge