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Overweight and obese women will both increase their chances of getting pregnant if they manage to lose some weight, conventional wisdom says.

Losing even a little weight helps, but reaching a healthy Body Mass Index offers the best chances. A newly published study into obesity and fertility has now shaken these believes. Being obese may not e healthy, but losing weight probably does not increase fertility.  

Researchers from the Penn State College of Medicine knew that obesity has a negative impact on a woman's ability to conceive, largely because obesity reduces ovulation rates. Lead researcher Richard Legro MD said: "Obesity, especially centered in the abdomen, among infertile women seeking pregnancy is associated with poor response to ovulation induction and with decreased pregnancy rates."

In reaction to that fact, most medical doctors would tell an overweight or obese woman who has been trying to conceive for a while without success to lose weight. Actually, an obese woman just going for a preconception health check would be told the same thing. Unfortunately, few studies suggest that losing weight improve pregnancy rates. Dr Legro and his team conducted their study to find out if it would. They followed 29 morbidly obese women (that means a BMI of 40 or more) who were of childbearing age. The study subjects underwent gastric bypass surgery and lost dramatic amounts of weight. Their progress and ovulation were tracked over the course of two years. Daily urine checks were part of the plan these tested the frequency and quality of ovulation. Before the gastric bypass operation, the ovulation rates were surprisingly high at 90 percent. The researchers did daily urine checks again (for the duration of one menstrual cycle) at one month after the operation, and two, three, six, 12 and 24 months.

The results? There was no change in the women's ovulation! The study team did find some other changes, however. Obese women are known to have longer menstrual cycles than those who are at a healthy weight. The main reasons for this is that their follicular phase of these women's cycles are longer. The follicular phase is the stage of the cycle lasting from the end of a period up till ovulation. It is not clear why obesity lengthens this stage of the menstrual cycle. The research team found that losing weight shortened this part of the cycle, by 6.5 days within three months of the operation and nine days after two years. Interestingly enough, the researchers did not ask the women who participated in the study if they wanted to get pregnant, and how often they had sexual intercourse.

They did use a questionnaire to determine the women's sexual desire, and found that the women's libido increased after the surgery significantly. There was no need to ask how often the study subjects had sex; the team figured there would be more sex if there was more sexual desire. Increased sexual desire was not found to have any connection with the women's hormone levels. Dr Legro said: "The effects of weight loss on reproductive function are more modest than we hypothesized. In terms of ovulation, there doesn't appear to be a window after surgery where fertility is improved. The door appears to be open at all times. Other factors may be involved with infertility in obese women, such as diminished sexual desire and thus less intercourse. This study, to our knowledge, is the largest, most comprehensive and longest study of female reproductive function before and after Roux en Y gastric bariatric surgery."

Keep in mind that 29 women is not that much, and that the results be be fascinating but not necessarily relevant to you personally, if you are struggling with this problem. There are many reasons to lose weight that don't involve your ovulation, and the researchers' conclusion that libido improves with gastric bypass surgery is only a small part of that! The study results don't apply to women with Polycystic Ovary Syndrome. Primarily a hormonal problem, PCOS is a different beast altogether. Other studies have shown that gastric bypass surgery can help PCOS sufferers get pregnant.

  • Photo courtesy of Tobyotter
  • Photo courtesy of Tobyotter

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