During pregnancy, the fetus draws nutrients from the mother’s blood flowing through the placenta in order to obtain amino acids, sugars, fatty acids, minerals, vitamins and other components necessary for growth and development. Therefore, pregnant women should consume a reasonable and balanced amount of nutrients throughout their pregnancy, which are essential for maintaining normal physiological metabolism of the pregnant woman and the growth and development of the fetus. Pregnant women who gain too little weight are at risk of nutritional deficiencies Gaining too little weight during pregnancy can neither meet their own nutritional needs nor provide adequate nutrition for the fetus. Common nutritional deficiencies during pregnancy include vitamin D, calcium, iron, protein and other nutrient deficiencies. Pregnant women may suffer from osteoporosis, anemia, and wasting, and the fetus may experience intrauterine growth and developmental restriction, low birth weight, and mental deficiencies, which can also lead to an increased incidence of miscarriage and preterm birth. In addition, pregnant women who gain too little weight have poor vaginal dilatation and weak muscles, and have a higher than normal chance of having a difficult labor. Pregnant women should gain weight moderately If pregnant women gain about 12 kg during pregnancy, it can effectively reduce the rate of preterm labor and stillbirth. However, if the weight gain is too much, it is prone to many complications, such as gestational hypertension syndrome, gestational diabetes, and blood clots. At the same time, due to fat accumulation, tissue elasticity is weakened, obese pregnant women are prone to hemorrhage during delivery. Obese pregnant women who are overnourished are highly susceptible to difficult labor, birth injuries, cesarean section, and chances of vaginal assisted delivery. At the same time, due to the thick abdominal fat of obese pregnant women, it will increase the difficulty of prenatal examination, thus unable to determine the fetal position. The emergence of overweight or huge children. Fetal mortality is high and abortion is easy. The incidence of stillbirth in obese pregnant women is two to four times higher than that of the general population. Newborns born to obese pregnant women are prone to neural tube defects such as anencephaly and spina bifida. Reasonable weight gain range standard Reasonable weight gain range, there is no good standard in China, at present, the commonly used standard is the standard in the guideline of Gestational Weight Gain (GWG) published by the International Federation of Internal Medicine (IOM) in 2009, see Table 1. This standard divides the pre-pregnancy body weight into 4 grades, i.e., wasting, normal, overweight, and obese. This classification standard comes from the WHO, which samples mostly European and American people. It is not very applicable because of the differences between Chinese people and Europeans and Americans in terms of genes and body size. Aggregate analysis of data from 13 large-scale epidemiological surveys conducted in China since 1990, totaling about 240,000 adults, concluded that the risk of hypertension in Chinese people with a body mass index ≥24 (BMI ≥24 kg/m2) is three to four times higher than that of people with a normal body weight (BMI=18.5-23.9 kg/m2), and the risk of diabetes mellitus is two to three times higher than that of people with a normal body weight. Among the 5 major risk factors including hypertension, hyperglycemia, high serum total cholesterol, high serum triglycerides, and lowered serum HDL cholesterol, the risk of having ≥2 risk factors in overweight or obese individuals is 3-4 times higher than that of normal-weight individuals, and >90% of the obese individuals with a BMI ≥28 kg/m2 suffer from the above mentioned disorders or have an aggregation of the above mentioned risk factors. Therefore, the Chinese office of the International Society for Life Sciences (ISLS) issued the recommended values of body mass index (BMI) for Chinese people in 2001, with BMI ≥24 kg/m2 as the threshold for overweight and BMI ≥28 kg/m2 as the threshold for obesity in Chinese adults. In our practical work, it can be adjusted to Table 2 according to the BMI standard of Chinese people.