Treatment of restriction in fetal growth with L-arginine

INTERVENTION: Pregnant women with an ultrasonographic diagnosis of IUGR will be invited to participate in the study. After signing informed consent, women will be randomised and assigned to one of two study groups: 1. Women in the L‐arginine group will take 1 packet/day containing 7.84 gram of L‐arginine 2. The placebo group will take 1 packet/day, identical in weight, size, color and flavor to those of L‐Arginine but that will only contain excipient without pharmacological activity (96% corn starch) Women will be instructed to take the packet at least one hour before breakfast in order not to interfere with the absorption of other constituents of the diet. The maximum treatment duration will be 20 weeks and the follow‐up will be done every week. CONDITION: Intrauterine growth restriction (IUGR) ; Pregnancy and Childbirth PRIMARY OUTCOME: Birth weight below the 10th percentile for gestational age and sex, according to local reference curves. The estimation of fetal weight is made by combining the cephalic perimeter, abdominal perimeter and femur length. This weight estimation is usually done every two weeks when the estimated fetal weight percentile is between the 3rd and 10th percentile and each week when it is below the 3th percentile. SECONDARY OUTCOME: ; Secondary objectives will be analyzed at the postnatal level, except for the diagnosis of the development of hypertension in pregnancy, either preeclampsia or gestational hypertension:; 1. Birth weight; 2. Gestational age at birth; 3. Size of the newborn; 4. Abdominal perimeter of the newborn; 5. Cephalic perimeter of the newborn; 6. Weight index of the newborn; 7. Placental weight; 8. Placental weight/weight ratio of the newborn; 9. Low weight (<2500 g); 10. Very low weight (<1500 g); 11. Preterm delivery <37 weeks of gestation; 12. Preterm delivery <32 weeks gestation; 13. Preterm delivery <28 weeks gestation; 14. Apgar score at minute 1 and 5; 15. Perinatal mortality (early fetal and neonatal mortality); 16. Respiratory distress syndrome; 17. Bronchopulmonary dysplasia; 18. Intraventricular hemorrhage; 19. Periventricular leukomalacia (selene); 20. Neonatal sepsis; 21. Necrotizing enterocolitis; 22. Retinopathy of prematurity; 23. Compound of perinatal morbi‐mortality; 24. Admission to the neonatal intensive care unit; 25. Congenital malformations; 26. Induction of labor; 27. Cesarean section; 28. Preeclampsia; 29. Gestational hypertension; 30. Antepartum hemorrhage; 31. Postpartum hemorrhage; 32. Maternal infection; 33. Need for maternal hospitalization; 34. Maternal adverse effects; INCLUSION CRITERIA: 1. Age =18 years 2. Single pregnancy 3. Ultrasonographic diagnosis of IUGR: estimated fetal weight lower than the 10th percentile for gestational age according to local or national reference values, independently of the results of the Doppler parameters of the umbilical, middle cerebral and/or uterine arteries 4. Live fetuses at 11 and 13 at weeks gestation 6. Gestational age between 24 and 32 weeks 7. No indication of imminent or planned birth 8. Availability to participate in the study and sign the consent