There are three possible reasons for the surge in weight gain during pregnancy despite not eating much, including excessive relative surplus calories, fetal development, and water and sodium retention. First of all, we need to clarify the reasons for weight gain, and then take corresponding intervention measures.1. Excessive relative surplus calories: not eating much, but not much calorie consumption, resulting in relative surplus calories and subcutaneous fat deposition will cause weight gain. In the whole pregnancy process, weight gain generally does not exceed 30 pounds, usually to achieve a balanced diet, eat less and more meals, can be combined with a small amount of activity exercise, such as walking, so that the weight slowly down; 2, fetal development: the gradual development of the fetal physique, amniotic fluid increase, placenta growth, will cause weight gain. It is recommended to go to the hospital for physical examination, routine blood tests and obstetric ultrasound examination. If the weight gain of pregnant women is caused by fetal development, it is usually a normal physiological phenomenon and is usually not treated, but if there is abnormal fetal development and abnormal amniotic fluid volume, it is necessary to cooperate with the doctor for treatment; 3. Water and sodium retention: In the middle and late stages of pregnancy, water and sodium retention in the body will lead to increased circulating blood volume and edema, thus causing weight gain. The presence of edema can be treated with appropriate methods, such as walking and massage. If the edema is serious, you should go to the hospital in time and be treated under the guidance of the doctor.