Extra weight might affect female reproductive function and make obstacles for conception, a study suggests.

British researchers carried out a study in which they analyzed correspondence between a woman's body-mass index (BMI) and fertility. The study involved 3000 women who had no evident reasons for infertility. The scientists have found out that every point after BMI 29 reduces chances for conception by 4 percent in comparison with women whose BMI is between 21-29.

BDI is the individual's body weight divided by the square of hearth. BMI may be accurately calculated using any of two formulas: BMI= weight (kg)/ height2 (m2) or weight lb * 703 / height2 (in2). This index was developed by Belgian sociologist and statistician Adolphe Quetelet.

Women with very high BMI (35-40) turned out to be 26-43 % less likely to get pregnant than women with normal BMI (21-29). According to doctors these figures should arouse concern as 12% of women in West Europe and 25 % of women in Northern America have extra weight.

Today most European women tend to plan pregnancy after 30. This fact plus obesity make a matter of concern, as both factors are proven to affect fertility.

Researchers from Amsterdam (Netherlands) suppose that leptin (hormone that controls appetite and consumption energy) hides itself in fat issues, if a woman suffers from obesity. Such hormonal misbalance affects the process of steroid production by ovaries. This reduces chances for pregnancy.