Maternal Overweight/obesity increases risk of GDM and macrosomia Objectives: Compare pregestational BMI. Frequency of macrosomia. Correlationship between BMI first trimester fasting glycemia (1stTFG>92) fasting glycemia OGTT (FGOGTT), glycemia 120 minutes OGTT (2HPG), maternal weight gain during pregnancy (MWG) and macrosomía Research Design Methods: Analysis of 120 GDM medical records using ALAD diagnostic criteria. BMI categories were compared in Groups A ≥30 vs. ≤24.9 B 25-29.9 vs. ≤24.9 C ≥30 vs. 25-29.9 Variables: maternal age (MA), 1stTFG>92; FGOGTT, 2HPG, birth weight (BW), HbA1c, maternal triglyceridemia on last trimester (MTAG) maternal weight gain (MWG) SPSS V22. Results: BMI ≥30 N:39 BMI 25-29.9 N:42 BMI≤24.9 N:33 Mean HBA1C for all groups 5%. Table 1 comparison groups. Macrosomía N:13 (N:5 BMI 25-29.9 N:8 BMI ≥30 N:0 BMI group ≤24.9) p0.026. Correlation of macrosomia and FG1stT> 92 FGOGTT 2HPG MWG ≥ 7KG in BMI ≥30 is p0.046 p0.017 p0.096 P0.0001 respectively. Correlation between macrosomia and FG1stT> 92 FGOGTT 2HPG MWG ≥ 11KG in BMI 25-29.9 is p0.0001 P0.011 p0.012 p0.001 respectively Discussion: Pregestational BMI excessive MWG 1stTFG and higher levels of MTAG in BMI ≥30 increases risk of macrosomia. 1stTFG> 92 should considered as an independent risk factor for GD/macrosomia in overweight/obese pregancys. In BMI ≥25 consider lower thresholds of FG for GDM diagnostic criteria to prevent macrosomia. Disclosure M. Argerich: None. R. David: None. A. Bocchini: None.