Low Glycemic Index Diet Management for Overweight Pregnant Women (LGIDMOPW)

• Maternal insulin [ Time Frame: from the randomization (<=12weeks gestation) to delivery (38-42 weeks gestation), an expected average of 25 weeks ] [ Designated as safety issue: No ]
  measured at first prenatal visit and last visit before delivery
  
  
• Cord blood C-peptide [ Time Frame: at delivery ] [ Designated as safety issue: No ]
  collect cord blood, seperate serum, and stored at -20 centigrade.
  
  
• Incidence of gestational diabetes [ Time Frame: from the randomization(<=12weeks gestation) to delivery (38-42 weeks gestation), an expected average of 25 weeks ] [ Designated as safety issue: No ]
  Proportion of women with newly incident diabetes during pregnancy
  
  
• macrosomia [ Time Frame: at birth ] [ Designated as safety issue: No ]
  Baby weight at delivery in grams is equal to or greater than 4000g.
  
  

• Incidence of gestational hypertension [ Time Frame: from the randomization(<=12weeks gestation) to delivery (38-42 weeks gestation), an expected average of 25 weeks ] [ Designated as safety issue: No ]
  Proportion of women with newly incident hypertension during pregnancy. Hypertension is defined as systolic and diastolic blood pressure equal to or greater than 140 / 90mmHg.
  
  
• birth weight [ Time Frame: at delivery ] [ Designated as safety issue: No ]
  
• cesarean delivery [ Time Frame: at delivery ] [ Designated as safety issue: No ]
  
• gestational age [ Time Frame: at birth ] [ Designated as safety issue: No ]
  
• premature delivery [ Time Frame: at delivery ] [ Designated as safety issue: No ]
  gestational age <37 weeks at delivery
  
  
• maternal gestational weight gain [ Time Frame: From baseline measurement to delivery: up to 9 months ] [ Designated as safety issue: No ]
  Increatment of body weight from that measured at first prenatal visit (at baseline) to last body weight measurement before delivery with precision of 0.5kg
  
  

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 consulation 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 consulation 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.