Appropriate pre-pregnancy weight and weight gain during pregnancy can lead to good pregnancy outcomes and promote maternal and child health. However, pre-pregnancy obesity and excessive weight gain during pregnancy not only increase the incidence of hypertension, diabetes, cesarean delivery and large babies, but also affect the risk of maternal and child health after delivery, and the risk of continued obesity and type 2 diabetes after delivery. Therefore, it is necessary to understand the risks of obesity on pregnancy and outcome. The prevalence of obesity among women in China According to data from the National Bureau of Statistics and the Health Planning Commission, both the overweight and obesity rates among Chinese people are increasing. From 1992 to 2015, the overweight rate rose from 13% to 30% and the obesity rate rose from 3% to 12%. Pre-pregnancy overweight accounted for 13.33% and obesity for 2.84% of the population, with a gradual increase with age. In 2016, the Lancet published a report on the Global Adult Weight Survey, which showed that 43.2 million men and 46.4 million women were obese in China, the highest total in the world. Maternal BMI in China Body mass index (BMI) = weight (kg) รท height^2 (m). BMI values of pregnant women: 25.01-30 for overweight, 30.01-40 for mildly obese group, and >40 for moderately obese group. Chinese pregnant women are 13.15% underweight, 56.45% normal, 19.2% overweight, and 11.2% obese. Reasons for overweight or obesity during pregnancy The survey shows that nearly 90% of pregnant women and their families believe that they must eat more during pregnancy to meet the nutritional needs of the fetus through the increase in BMI during pregnancy, and that the bigger the child born, the better to carry. In addition, many people do not know enough about exercise during pregnancy and believe that they should eat more and move less. In addition, community and hospital education is not in place, as well as genetic and environmental factors. Obesity on fertility The fertility rate of normal weight women is 30% per cycle, and the cumulative annual fertility rate is 84%. ART treatment can get similar fertility rate. Conception rates per cycle are lower in women with simple obesity, and the success rate of ART decreases with increasing obesity. Polycystic ovary syndrome, hyperandrogenemia, and insulin resistance are among the most common gynecologic endocrine disorders, with the main clinical manifestations being obesity, hirsutism, acne, and scanty or amenorrheic menstruation. Weight loss can increase the chances of conception by spontaneous or induced ovulation. 1. Obese people are prone to miscarriage The relative low estrogen and progesterone are more obvious in the advanced age. Obesity causes a decrease in ovarian function and egg quality, thus affecting the quality of fertilized eggs and causing genetic material to be prone to aberrations or abnormalities. 2, obese people are prone to a variety of diseases obesity is a disease, serious people can reduce life 8 years, may also induce a variety of diseases and cancer. Obesity or increase the risk of 10 kinds of cancer, especially breast cancer and uterine cancer. For every 5 increase in body mass index from normal, the risk of uterine tumors increases by 62% and cervical cancer by 10%. The risk of endometrial cancer increases by 3 times for those who exceed 9-20 kg of normal body weight and by 10 times for those who exceed 20 kg. The incidence of uterine fibroids, endometritis and uterine polyps increases; thyroid disease, chronic hypertension, diabetes and other comorbidities increase. 3, maternal mortality rate increased related research shows that the death of obesity accounted for 35% of maternal mortality. Obesity is a high risk factor for gestational diabetes, thromboembolism, hypertension and cesarean section. The growing problem of female obesity has become a major obstetric safety concern. The effect of obesity on pregnancy The increased water and sodium retention and adipose tissue in pregnancy can cause abnormal lipid metabolism, resulting in hemodynamic changes and blood concentration, leading to hypertensive disorders during pregnancy. It is 2 to 3 times higher than normal. Gallaway et al. studied 14230 pregnant women and found that the risk of hypertensive disorders in pregnancy was 1.74, 3.00, and 4.87 times higher in the overweight, mildly obese, and moderately obese groups, respectively, than in the control group. Globally, an estimated 2.8 million women of childbearing age have type 2 diabetes and it affects 16.4% of pregnant women. Some studies have reported that 3% to 5% of people with GDM can develop type 2 diabetes after delivery.GDM has a tremendous impact not only on the health of the mother, but also on the health of the child in the long term. Risk factors include obesity, advanced age, polycystic ovary syndrome, previous GDM and family history of type 2 diabetes, with pre-pregnancy obesity and excessive weight gain during pregnancy being the most important contributing factors, and increased insulin resistance due to excessive weight gain during pregnancy may further worsen physiological insulin resistance, thereby increasing the risk of GDM. Gallaway et al. studied 14230 pregnant women and found that overweight GDM was 1.78 times more common in the control group, 2.95 times more common in the mildly obese group, and 7.44 times more common in the moderately obese group. The effect of obesity on labor and delivery Maternal obesity during labor and delivery is associated with the accumulation of pelvic adipose tissue, which reduces the available space and increases the chance of cephalopelvic disproportion; in addition, the accumulation of adipose tissue and poor muscle strength are often associated with weak uterine contractions and slow progress of labor, which may require vaginal assisted labor (forceps, negative pressure suction), cesarean delivery and increased risk of postpartum hemorrhage. Gallaway et al. reported a progressive decrease in the number of negative births with increasing BMI in the overweight, mildly obese, and moderately obese groups, with a 33.5% decrease in primiparous and 23.6% decrease in transitional births. The effect of obesity on the offspring The excessive weight gain of pregnant women leads to a generally heavy fetus, which becomes a huge child and is more prone to many complications than a normal weight child. Obese pregnant women, even moderately overweight, are at increased risk of stillbirth and are an important risk factor for neural tube abnormalities in the offspring. It is known that obesity is polygenic. If one parent is obese, 40% of the children will be obese; if both parents are obese, 70% of the children will be obese. Its development is related to genetic factors, environmental factors, social factors, psychological factors and other factors. The offspring’s long-term health, including hypertension, dyslipidemia, cardiovascular disease, insulin resistance and other diseases increase. Countermeasures Strengthen pre-pregnancy education and knowledge dissemination during pregnancy, effective weight control during pregnancy, and reasonable diet. Live a regular life, ensure sleep and appropriate exercise. Keep a calm state of mind, eliminate tension and prevent depression during pregnancy. Pre-pregnancy counseling, especially for women with high-risk factors who wish to have another child, need to fully assess the risk of pregnancy and intervene in pregnancy complications. Physical examination during pregnancy, including weight, blood pressure, blood glucose, thyroid function; menstrual status, presence of gynecological tumors; history of previous cesarean section and attention to the condition of the uterine incision. Different monitoring charts can be used to monitor weight gain according to different pregnant women in order to control maternal and child weight, reduce pregnancy complications, and promote vaginal delivery. Have correct knowledge and psychological preparation for pregnancy and delivery, and have trust in medical staff to cooperate with the completion of labor and delivery process. Dietary management during pregnancy Dietary characteristics of early pregnancy: most pregnant women have a poor appetite, partial eating, nausea, vomiting and other early pregnancy reactions. It is recommended that there is no need to force hard to eat. You can eat less and more meals, light and tasty, nutritious and easy to digest food. Dietary characteristics in the middle stage of pregnancy: early pregnancy reaction disappears, appetite improves, food quantity increases, and attention is paid to nutrition allocation. Eat more food with more protein, vitamins, calcium and iron. Keep a balance of various nutrients to ensure the needs of fetal development and growth. Do not consume too many carbohydrates. Dietary characteristics of late pregnancy: The fetus is growing rapidly, especially in the 8th and 9th months, and the fetal weight increases by 200 grams per month, and at the same time, a certain amount of nutrition is reserved for delivery and breastfeeding. Therefore, in addition to protein, sugar and fat, various vitamins and minerals should be added. Eat small meals and exercise moderately to prevent stomach pressure symptoms. In conclusion After the full liberalization of “two children” in China, there are more older women who are pregnant or preparing to have a second child, and some of them have metabolic diseases such as diabetes or abnormal lipid metabolism such as overweight or obesity and abnormal blood sugar before pregnancy. Early intervention and treatment must be done before pregnancy. Diet and physical activity can intervene and reduce the effects of obesity during pregnancy, and are effective ways to reduce the risk of HDP and GDM. Appropriate pre-pregnancy BMI and weight gain during pregnancy not only contribute to good maternal and infant health and birth outcomes, but also help mothers to recover postpartum weight and prevent overweight and obesity in children. Therefore, weight and nutrition management during pregnancy must be emphasized.