Infant Mortality; Infant, Very Low Birth Weight; Adrenal Cortex Hormones/administration & dosage; Apgar Score; Birth Weight; Cause of Death; Cesarean Section; Congenital Abnormalities/mortality; Delivery, Obstetric/methods; Female; Gestational Age; Humans; Hypertension; Infant, Newborn; Infant, Premature; Intensive Care, Neonatal; Logistic Models; Male; Odds Ratio; Pre-Eclampsia; Pregnancy; Pregnancy, Multiple; Prospective Studies; Pulmonary Surfactants/administration & dosage; Respiration, Artificial; Respiratory Distress Syndrome, Newborn/mortality; Risk Factors; Sex Factors; Tocolysis