The study is a randomized, single-blinded, controlled intervention trial to compare the effect of a low glycemic index diet versus diet recommended by the Chinese Dietary Guide for Pregnant Women on maternal and neonatal insulin resistance and adverse gestational events.

Overweight in pregnant women increases maternal insulin resistance and risk of adverse pregnancy outcomes. Recent evidence from both animal studies and human subject studies shows that adverse environmental exposures during pregnancy result in adverse influence on offsprings. The hypothesis of the current study is that the healthy intervention during pregnancy to overweight pregnant women--low glycemic diet, may improve the maternal and neonatal insulin resistance at birth.

The current study adopts randomized, single-blinded, controlled intervention trial, gives low glycemic index diet intervention based on the national diet and physical activity recommendations for pregnant women to the intervention group and only national diet recommendations to the control group. Four diet consultation interviews will be done,at baseline (first prenatal examination), the end of the 1st trimester, the 2nd trimester and the 3rd trimester respectively, including diet assessment and diet consultation specifically to adopting low glycemic diet. Glycemic load of diet will be calculated based on 24 hour diet recall data for each individual at every visit to help to lower their diet glycemic load by modifying some daily foods. The effect of intervention is investigated by comparing the insulin resistance levels between the two arms at birth and when infants are at age 2. For discrete traits, such as incidence of gestational diabetes and gestational hypertension, Person's chi-square tests were used. For continuous traits, such as insulin resistance index, maternal weight gain and neonatal birth weight, we use t-tests for comparisons between two groups. The study expects that long-term low GI diet intervention have beneficial effects on controlling maternal and neonatal insulin resistance to overweight women and long term health.

Inclusion

• Singleton pregnancy;
• Pregnant women with BMI≥24 kg/m2 at first antenatal examination;
• aged 18 years to 45 years;
• The week of first prenatal examination equal to or less than 12 weeks;
• Take routine prenatal examination;
• Willing and able to give informed consent. Exclusion
• Artificial impregnation;
• History of hypertension, diabetes, coronary heart disease or mental disorder;
• With Special diet habit(e.g. vegetarianism/ veganism).