TABLE 1.

Neonatal clinical variables included in this study.

Variables	Definition
Mother/pregnancy
Toxic habits	Smoking
Reproductive/Gynecological	Fertilization treatments, previous preterm births
Medical condition	Diabetes mellitus, hypertension
Intrapartum
Amniorrhexis	Prelabor rupture of membranes.
Pre-eclampsia	Hypertension, proteinuria, and edema after the 20th week of gestation
Mode of delivery	Normal vaginal, cesarean, emergency cesarean, elective cesarean
Fetal presentation	Unknown, cephalic, podalic, bottom, transverse
Neonatal
Gestational age (weeks)	Positive ultrasonography, last menstrual period, clinical assessments
Apgar scores at 1′ and 5′	Scores from 1 to 2 of Appearance, Pulse, Grimace, Activity, Respiration
Respiratory
Respiratory distress	Bronchopulmonary dysplasia, oxygen dependency, apnea, hyaline membrane disease
Bradycardia	Heart rate <100 l pm
Pulmonary hemorrhage	Positive bronquial aspiration for blood and respiratory deterioration
Pulmonary hypertension	Superior right limb and left inferior limb gradient in oxygen saturation >5% + hypoxemic trend
Pneumothorax	Thorax x-ray confirmation of air in pleural space
Asphyxia	Metabolic acidosis in umbilical cord pH + neonatal encephalopathy + background of alterations in cardiotocographic fetal exploration
Cardiac hemodynamic
Systolic murmur	Positive auscultation for heart murmur
Patent ductus arteriosus	Sistolc murmur + tensional gradient + bounding pulses and respiratory deterioration. Arterial flow between aorta and pulmonary artery shown via bidimensional echocardiography
Hypertension	Systolic pressure higher than percentile 90 Hg for gestational age
Hypotension	Mean arterial blood pressure lower than the gestational age during the first 3 days
Jaundice of prematurity	Increased bilirubinemia over birth weight expressed in g/100
Anemia	Level of hemoglobin in blood count <12 g/dl
Thrombocytopenia	Level of platelets <100.000/mm3
Coagulopathy	Altered of activated partial thromboplastine time or prothrombine time
Ultrasound brain abnormalities
Periventricular leukomalacia	Unilateral/bilateral hypo-echogenicity areas in brain parenquima adjacent to lateral boundaries of the ventricular system.
IV hemorrhage	Unilateral/bilateral abnormally extensive hypo-echogenicity areas in the ventricular system
Hydrocephalus	Symmetric bilateral increased size of the ventricular system
Microcephaly	<Percentile 10
Neurological
Cerebral palsy	Chronic disability of central nervous system origin characterized by aberrant control of movement and posture, appearing early in life
Severe mental retardation	Severely retarded individuals have IQ scores of <40
Seizures/Epilepsy	Presence of convulsive movements with or without electroencephalography correlation
Tetraplegia, diplegia	Paralysis affecting the four limbs, paralysis affecting symmetrical parts of the body
Inflammatory
Sepsis	Clinically, symptoms and alterations from laboratory results compatibles with infection with negative cultures. Confirmed, symptoms of infection + blood culture or urine culture and/or positive cerebrospinal fluid
Necrotizing enterocolitis	Digestive tolerance alteration necrotizing enterocolitis type II or higher
Otitis	Otic pain + positive symptom with compatible eardrum exploration
Conjunctivitis	Presence of conjunctival pus drainage
Ophthalmic
Retinopathy of prematurity	Defined according to the criteria established by the Committee for the Classification of Retinopathy of Prematurity (The International Classification of Retinopathy of Prematurity| Neonatology | JAMA Ophthalmology | The JAMA Network)
Medical treatments
Red blood cell transfusion	Hemoglobin level below 10 g/dL or hematocrit falls below 25%
Oxygen therapy	Oxygen is applied up to get saturations of 90–95% in pulse oxymetry
Mechanical ventilation	Mechanically assist or replace spontaneous breathing
Surgery	Any surgery during hospitalization