Being overweight is more than a risk for your health: it can completely end up your lineage. Being too skinny translates too low sex drive and sterility, in both women and men, but the opposite too seems to strike on fertility level: a new Dutch research published in the Human Reproduction journal shows that an overweight woman's chances of getting pregnant gradually decrease with her weight gain.

The research at the Academic Medical Center in Amsterdam was performed on 3,000 female subjects with fertility problems and there was a 4% decrease in the chances of pregnancy for each supplementary body mass unit (BMI), obese women displaying the lowest level of fertility.

Most previous studies focused on the high health risks in both the mother and the baby, while the new study focused on women trying to have a baby, looking for a link between their body mass and the results.

Body mass index (BMI) represents the weight in kilograms divided by the square of the height in meters. A value of 25 to 30 is considered overweight, and over 30 are cases of obesity. All the subjects presented fertility issues without an obvious reason as they were still ovulating normally and some got pregnant naturally.

The research encountered a strong relationship between their BMI and their chances of getting pregnant. Exceeding the value of 29 for BMI proved risky: every extra BMI point between 30 and 35 caused a 4% decrease in the chances of getting pregnant. Severe case of obesity, with BMI values over 35 presented a fertility rate lowered by 26% and 49% as compared to women having a BMI value of 21 to 29.

"Given the increased prevalence of obesity, this is a worrying finding. We think that women should be informed about their lower pregnancy chances due to their overweight. We hypothesize that losing weight will increase the chance to conceive without treatment", said lead researcher Dr. Jan Willem van der Steeg.

In November 2007 the British Fertility Society even urged its members to withhold IVF treatment from obese women until they managed to lose weight.