Maintaining body weight within a healthy range is an important part of good reproductive health. Extremes of weight on either side, either very thin or obese, increase a woman's risk of pregnancy difficulty.
Reproductive hormones are critical to pregnancy success.
Because these hormones are dependant on fat for their normal production and metabolism, body composition and fat stores directly effect their activity. Both very low and very high body fat stores, reflected in weight, can change the body's reproductive abilities. In addition, some chronic diseases are more likely to accompany higher or extremely low weights. Any pre-existing disease will add stress to pregnancy and may effect one's reproductive ability. BMI is used by health professionals to screen adults for their health risks related to weight.