Fetus 2~3 weeks small may be due to the calculation of pregnancy week is wrong, but also does not rule out pathological factors such as intrauterine growth restriction, etc., can be supplemented through nutrition, at the same time, treatment of the original disease, to promote the healthy development of the fetus. 1. Incorrect calculation of gestational week: if the pregnant woman had irregular menstruation before pregnancy, the time of fertilization may be later than the calculation, so the actual number of weeks of pregnancy will be smaller, and there will be a situation in which the fetus is smaller than 2-3 weeks, and it is necessary to verify the gestational week and then make a comprehensive judgment. 2. Fetal intrauterine growth restriction: If the ultrasound indicates that the size of the fetus is in line with the month of menopause at the beginning, but later becomes smaller, we should consider the situation of fetal intrauterine growth restriction. During pregnancy, pregnant women should do a good job of health care, nutrition and diet should be reasonable, and at the same time need to treat the primary disease, improve placental blood perfusion. If a pregnant woman has a fetus that is 2 to 3 weeks small, it is recommended that she consult a doctor in a timely manner, under the guidance of the doctor, complete the relevant examinations, identify the cause of the disease, and then treat the cause of the disease.