Statistical studies have shown a significant correlation between maternal pregestational weight and duration of pregnancy (i.e., a low weight may cause a shortening of pregnancy). Duration of pregnancy is further correlated to the weight gain (i.e., it is shortened by an insufficient gain). This phenomenon is observed in thin women, but not in women of heavy weight before the pregnancy.

The studies of weight losses obtained through hypocaloric or sodium-free diets or diuretics, show that a sudden weight loss may cause a shortening of pregnancy duration. This is verified in patients with normal or insufficient weight gain and starting with a normal or small weight, but not in overweight patients or with an important weight gain.

This study demonstrates the dangers of excessive measures toward prevention of toxemia. The decision of compulsive weight loss in mothers with multiple pregnancy must be well thought and carefully applied, for excessive measures could reduce the duration of pregnancy and thus increase the risks of perinatal death.