The PREDG study: testing whether an educational intervention can prevent excess weight gain during pregnancy

INTERVENTION: The randomisation will be automatically generated by a informatic program that assigns an random number to consecutive patients. The intervention arm will have an educational session about an adequate diet and physical activity. Diet will be calculated for the initial BMI, physical activity and pregnancy specific necessities. Both arms will receive information about an adequate gestational weight gain. Both arms will have biochemical determinations: basic, lipid profile, thyroid hormones, body impedance and weight and waist measurement. Follow up will continue for 6 months after delivery. CONDITION: Gestational weight gain in obese women ; Pregnancy and Childbirth ; Excessive weight gain in pregnancy PRIMARY OUTCOME: Gestational weight gain will be measured using weight (kg) in each monthly visit minus weight before pregnancy. SECONDARY OUTCOME: ; 1. Pregnancy complications:; 1.1. Gestational hypertension as arterial pressure >= 140 and/or 90 mmHg confirmed twice; 1.2. Gestational diabetes as defined by NDDG criteria; 1.3. Preterm birth as birth before 37 weeks of pregnancy; 1.4. Cesarean section as rate of cesarean section; 1.5. Macrosomia as neonatal birthweight >= 4 kg; 1.6. Small as neonatal birthweight < 10th percentile for gestational age and sex; 2. Postpartum weight retention as weight 6 months postpartum minus prepregnancy weight (kg).; INCLUSION CRITERIA: 1. BMI = 30 kg/m2 prior to becoming pregnant