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Deleterious Effects Described in Obese Women Undergoing IVF

Impact of Bodyweight and Lifestyle on IVF Outcome: Expert Commentary

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Expert Commentary

Infertility is an increasing health problem in Western societies. As a consequence, the number of IVF cycles performed has increased sharply in recent decades. Nowadays, in the best scenario, pregnancy rates per embryo transfer do not exceed 50-60%, increasing up to 70% when donated ova are employed. A more accurate selection of patients for a specific ART, individualized ovarian stimulation protocols and improvement of embryo selection criteria and laboratory management could help to increase these chances. However, several limiting environmental factors constitute obstacles to surpassing current ceilings of success. Some of these lifestyle factors could be avoided or modified. They should be one of the first targets through which pregnancy chances could be improved, not only in IVF but in all methods of conception.

There are few studies that explore the relation between IVF and illicit or licit drugs, such as alcohol, caffeine, marijuana or cocaine, among others. Regardless of the scarcity of evidence, the health risks for both men and women of consumption of these substances are well known, during and outside the pregnancy. Hence, IVF patients should be encouraged to discontinue or at least reduce their use before conception without the need for corroboration by further studies which are, in addition, difficult to perform prospectively from an ethical point of view. In fact, current information has been obtained principally from a few poorly designed retrospective human studies using small sample sizes. The same advice can be given with respect to smoking. Nevertheless, in this field, an extensive medical literature has demonstrated multiple harmful effects of smoking for human health, including fertility. The research field in this area should be limited to determine more accurately the deleterious effect of these drugs on reproduction and perhaps the cut-off at which these substances are truly harmful. In short, current evidence is reliable enough to give solid advice to the patients regarding giving up these habits.

However, other lifestyle factors, such as bodyweight, psychological stress and occupational exposure to pollutants require further research, as current knowledge is conflicting or scant. Occupational or domestic habits (e.g., mobile phone use) are a new focus of attention, as they seem to contribute to infertility, though how this occurs is still to be established. With respect to psychological stress, the current disagreement found among the medical literature is due to the inappropriate design of the studies performed. Most of these have been retrospective or cross-sectional, psychological measurements have usually been limited to a single stress parameter, IVF end points beyond pregnancy have rarely been assessed, varying psychological conditions have been evaluated together, several periods of time prior to the IVF cycle have been considered with heterogeneous and often small sample sizes, and examination tests based on questionnaires biased by patient self-perception of the index problem have been employed.

Bodyweight has been assessed more thoroughly, although the consequences of being underweight have received less attention that the effects of weight excess, due to the lower prevalence of this condition. Further studies are necessary in order to understand the full implication for fertility of undernutrition, especially according to its association with or without menstrual disturbances. However, weight excess has been proven to impair fertility. Current and future research should focus on how, where and why this occurs. Gametes, embryos, the endometrium and their environments seem to be affected by weight excess, but the real implication for each of these will only be fully understood when adequately designed studies are performed.

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