Two clinical trials report that obese women who develop GDM have a higher risk of adverse perinatal outcomes than normal weight women with GDM. In addition, caloric restriction (~70% DRI for pregnant women) can result in a considerable slowing of maternal weight gain in obese women with GDM, without causing maternal or fetal compromise and/or ketonuria.  Four studies report that both prepregnancy underweight (BMI<19) and obesity (BMI>30) are associated with an increased risk of preterm delivery.  However, low or inadequate weight gain during pregnancy, not excessive weight gain, is associated with an increased risk of preterm delivery, regardless of prepregnancy BMI levels.

• Grade I means there is Good/Strong evidence supporting the statement;
• Grade II is Fair;
• Grade III is Limited/Weak;
• Grade IV is Expert Opinion Only;
• Grade V is Not Assignable.
• High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
• Moderate (B) means we are moderately confident in the effect estimate;
• Low (C) means our confidence in the effect estimate is limited;
• Very Low (D) means we have very little confidence in the effect estimate.
• Ungraded means a grade is not assignable.

Two studies were evaluated to investigate caloric intake and appropriate weight gain. Research on caloric requirements is limited: Further research is needed on the determination of caloric requirements in women with gestational diabetes mellitus.

• Grade I means there is Good/Strong evidence supporting the statement;
• Grade II is Fair;
• Grade III is Limited/Weak;
• Grade IV is Expert Opinion Only;
• Grade V is Not Assignable.
• High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
• Moderate (B) means we are moderately confident in the effect estimate;
• Low (C) means our confidence in the effect estimate is limited;
• Very Low (D) means we have very little confidence in the effect estimate.
• Ungraded means a grade is not assignable.