The term describes women who are so obsessed with staying thin that they're trying to keep the weight off, even while their pregnant.
Doctors say that it can cause birth defects, premature delivery and pre-term labor.
Ideally, a healthy weight gain should be about 25 to 35 pounds for women who are at a normal weight.
A healthy weight gain for overweight women is 15 to 20 pounds and obese women should only gain 11 to 20 pounds.
The more that larger women gain, the more likely they are to develop high blood pressure or gestational diabetes.
