Objective: To test the prognostic value of the pregnant nutrition graph (Vallop Curve).
Design: Prospective and comparative study.
Setting: Department of Obstetrics and Gynecology, Prangnangklao Hospital.
Subject: 510 cases who attended the antenatal care clinic and delivered at Prangnangklao Hospital from January 2004 to July 2004.
Material and Method: Height, weight and pre-pregnancy body mass index (BMI) of the women were recorded and classified BMI of each into 3 groups, low BMI (< 19.8) normal BMI (19.8-26.0) and high BMI (26.1-29.0.) The weight of the pregnant women in each gestational week was calculated as percentage of standard BMI at 21 and plotted in a Vallop Curve. The data was analyzed by using an Anova Test and Wilson Method to find association. A p-value of < 0.05 was regarded as significant.
Outcome evaluation: Birth weight curve, below the 2,500 gm line and above the 2,500 gm line.
Results: The mean birth weight of low BMI was 2,541.70 + 276.89 gm. The mean birth weight of normal BMI was 3,021.30 + 318.61 gm. The mean birth weight of high BMI was 3,520.00 + 250.65 gm. There was a significant difference in weight by the Anova Test. Sensitivity was 65.6%. Specificity was 87.4%. Positive predictive value was 42.9%. Negative predictive value was 94.7%. P-value was < 0.001 at 95% confident interval by the Wilson Method.
Conclusions: The Vallop Curve may be useful to predict the incidence low birth weight infants, but in the future the Vallop Curve may be changed corresponding to change of socio-economic status and also to simplify it’s method of usage.

Keywords: Body mass index (BMI), Pregnant nutrition graph (Vallop Curve), Low Birth weight (LBW)