title: [Risk factors for preterm deliveries in a public hospital].
abstract: BACKGROUND
  Preterm births are responsible for 75 to 80% of perinatal mortality.
  
  
  OBJECTIVE
  To determine the factors associated with preterm births, using maternal clinical data, laboratory results and pathological placental findings.
  
  
  METHODS
  Retrospective study of 642 preterm single births at 22-34 weeks' gestation. Four hundred and seven cases with pathological placental studies were included. Births were subdivided into preterm births as a consequence of a medical indication and spontaneous births with or without premature rupture of membranes (PROM). Risk factors for preterm births were classified as maternal, fetal, placental, indeterminable and unclassifiable.
  
  
  RESULTS
  The proportions of preterm births were spontaneous 69% (with PROM 27% and with intact membranes 42%) and medically indicated births 31%. A risk factor associated with prematurity was identified in 98 and 85% of medically indicated and spontaneous births, respectively. Ascending bacterial infection (ABI) was the most frequently associated factor with spontaneous preterm delivery in 51% of women (142/280, p < 0.01) and with preterm births of less than 30 weeks in 52% of women (82/157, p < 0.01). Vaginal or urinary infection with Group B Streptococcus, was the most common clinical condition associated with ABI related deliveries. Hypertension was present in 94 of 127 medically indicated preterm deliveries (preeclampsia in 62% and chronic hypertension in 12%), and in 29% (preeclampsia 24%) of preterm births of more than 30 weeks. Congenital anomalies were mainly associated with a maternal age over 35 years in 15% (14/92) of women. The frequency of placental diseases was higher in spontaneous preterm deliveries (14%) and in pregnancies of more than 30 weeks in (14%).
  
  
  CONCLUSIONS
  ABI was the most common factor associated with spontaneous preterm births at 2234 weeks, while preeclampsia is the most common factor associated with medically indicated preterm births.
authors.affiliation: Servicio y Departamento de Obstetricia, Ginecología y Neonatología, Hospital San Borja ArriaránChile.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Ovalle
authors.forename: Elena
authors.initials: E
authors.lastname: Kakarieka
authors.forename: Gustavo
authors.initials: G
authors.lastname: Rencoret
authors.forename: Ariel
authors.initials: A
authors.lastname: Fuentes
authors.forename: María José
authors.initials: MJ
authors.lastname: del Río
authors.forename: Carla
authors.initials: C
authors.lastname: Morong
authors.forename: Pablo
authors.initials: P
authors.lastname: Benítez
mesh_terms: D000293:Adolescent; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D005260:Female; D006779:Hospitals, Public; D006801:Humans; D007231:Infant, Newborn; D008875:Middle Aged; D007752:Obstetric Labor, Premature / Q000453:epidemiology / Q000209:etiology*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011264:Pregnancy Trimesters; D012189:Retrospective Studies; D012307:Risk Factors; D012959:Socioeconomic Factors; D055815:Young Adult