title: Correcting haemoglobin cut-offs to define anaemia in high-altitude pregnant women in Peru reduces adverse perinatal outcomes.
abstract: OBJECTIVE
  To determine if correction of cut-offs of haemoglobin levels to define anaemia at high altitudes affects rates of adverse perinatal outcomes.
  
  
  METHODS
  Data were obtained from 161,909 mothers and newborns whose births occurred between 1,000 and 4,500 m above sea level (masl). Anaemia was defined with or without correction of haemoglobin (Hb) for altitude as Hb <11 g/dL. Correction of haemoglobin per altitude was performed according to guidelines from the World Health Organization. Rates of stillbirths and preterm births were also calculated.
  
  
  RESULTS
  Stillbirth and preterm rates were significantly reduced in cases of anaemia calculated after correction of haemoglobin for altitude compared to values obtained without Hb correction. At high altitudes (3,000-4,500 masl), after Hb correction, the rate of stillbirths was reduced from 37.7 to 18.3 per 1,000 live births (p < 0.01); similarly, preterm birth rates were reduced from 13.1 to 8.76 % (p < 0.01). The odds ratios for stillbirths and for preterm births were also reduced after haemoglobin correction.
  
  
  CONCLUSIONS
  At high altitude, correction of maternal haemoglobin should not be performed to assess the risks for preterm birth and stillbirth. In fact, using low altitude Hb cut-off is associated with predicting those at risk.
authors.affiliation: Department of Biological and Physiological Sciences, Universidad Peruana Cayetano Heredia, Honorio Delgado 430, Lima 31, Peru, gustavo.gonzales@upch.pe.
authors.forename: Gustavo F
authors.initials: GF
authors.lastname: Gonzales
authors.forename: Vilma
authors.initials: V
authors.lastname: Tapia
authors.forename: Manuel
authors.initials: M
authors.lastname: Gasco
mesh_terms: D000328:Adult; D000531:Altitude; D000740:Anemia / Q000150:complications / Q000453:epidemiology*; D005260:Female; D005865:Gestational Age; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D016017:Odds Ratio; D010568:Peru / Q000453:epidemiology; D011247:Pregnancy / Q000097:blood*; D011256:Pregnancy Outcome; D037841:Pregnant People; D047928:Premature Birth / Q000453:epidemiology*; D012016:Reference Values; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D050497:Stillbirth / Q000453:epidemiology*; D055815:Young Adult
chemical_list: D006454:Hemoglobins