Background. Inappropriate of gestational weight gain could become as obesity risk factor to mother and their offsprin's. Understanding the influence and interaction between placental metabolic hormones with maternal daily living on increase of maternal body fat is important for developing a more appropriate gestational weight gain guidelines.

Aim. Our current study will investigate whether the pre pregnancy BMI, dietary intakes, and leptin resistance induced by human placental lactogen, are associated with changing of body fat mass on pregnant women.

Method. This observational longitudinal study will be conducted in North Sulawesi from January 2015 to December 2015. Dietary information was collected through a semi quantitative food frequency questionnaire covering an extensive list of foods and beverages which includes in Indonesian Nutrition Composition Tables. Measurement of fat mass performed by measuring upper arm circumference (UAC) and body fat percentage using bioelectrical impedance analysis. Plasma leptin and human placental lactogen will analyze using ELISA method. Several variables with confounding potential were controlled for, namely, insulin levels and several maternal sociodemographic. Statistic analytic performed by SPSS 19 program. The data presented in mean with SD or median. Comparation between two variables using T test, to access the strength of influence between independent variables a multivariate multiple linear regression will be used and Pearson correlation with significance p<0.05. Ethical clearance has been approved by Tim Pertimbangan Etik Penelitian Kesehatan (TPEPK) BLU RSUP Prof.Dr.R.D.Kandou Manado. No. TPEPK 081401.

Key words: gestational weight gain, body fat, nutrition, human placental lactogen, leptin