title: Malaria and gravidity interact to modify maternal haemoglobin concentrations during pregnancy.
abstract: BACKGROUND
  Primigravidity is one of the main risk factors for both malaria and anaemia. Since the implementation of intermittent preventive treatment (IPTp) in sub-Saharan Africa, the relationship between anaemia and gravidity and its evolution during pregnancy has been little explored. This study aimed to evaluate the impact of gravidity on the variation of haemoglobin during pregnancy according to the timing of gestation.
  
  
  METHODS
  Data from three studies carried out in nearby areas in south Benin (Ouidah, Comé, Allada) between 2005 and 2012 were analysed. At inclusion (first antenatal visit, ANV1) women's age, area of residence, schooling, gravidity, gestational age, weight and height were recorded. Thick blood smears were performed on ANV1, second visit (ANV2) and at delivery. In Allada, women's serum ferritin and CRP concentrations were also assessed. The impact of gravidity on maternal haemoglobin (Hb) was analysed using a logistic or linear regression depending on the outcome. The statistical significance was set to P < 0.05.
  
  
  RESULTS
  In total, data from 3,591 pregnant women were analysed. Both univariate and multivariate analyses showed a constant association between Hb concentrations and gravidity in the three periods of Hb assessment (ANV1, ANV2 and delivery). Mean Hb concentration was significantly lower in primigravidae than in multigravidae at ANV1 (mean difference = -2.4 g/L, CI 95%: [-3.4, -1.4], P < 0.001). Afterwards, there was a significant increase in primigravidae only, with a tendency to reversal between primigravidae and multigravidae, which was confirmed at delivery (mean difference = 2.8 g/L, CI 95%: [1.3, 4.2], P < 0.001). The prevalence of malaria infection was halved between ANV1 and delivery in primigravidae while it decreased by only 38% among multigravidae, who were less prone to malaria infection (prevalence at ANV1, 20% and 10% respectively). Iron deficiency was more common in multigravidae, and it decreased slightly in this group between ANV1 and delivery.
  
  
  CONCLUSIONS
  In a context of IPTp, Hb levels improved progressively throughout pregnancy in primigravidae, likely as a result of reduction in malaria infection. In multigravidae, the improvement was less perceptible and anaemia was mainly due to iron deficiency.
authors.affiliation: Mère et enfant face aux infections tropicales, IRD Unité mixte de recherche 216, Paris, France. smaila11@yahoo.fr
authors.forename: Smaïla
authors.initials: S
authors.lastname: Ouédraogo
authors.forename: Florence
authors.initials: F
authors.lastname: Bodeau-Livinec
authors.forename: Valérie
authors.initials: V
authors.lastname: Briand
authors.forename: Bich-Tram
authors.initials: BT
authors.lastname: Huynh
authors.forename: Ghislain K
authors.initials: GK
authors.lastname: Koura
authors.forename: Manfred M K
authors.initials: MM
authors.lastname: Accrombessi
authors.forename: Nadine
authors.initials: N
authors.lastname: Fievet
authors.forename: Achille
authors.initials: A
authors.lastname: Massougbodji
authors.forename: Philippe
authors.initials: P
authors.lastname: Deloron
authors.forename: Michel
authors.initials: M
authors.lastname: Cot
mesh_terms: D000328:Adult; D000740:Anemia / Q000453:epidemiology*; D000962:Antimalarials / Q000627:therapeutic use; D001541:Benin / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D008288:Malaria / Q000150:complications* / Q000188:drug therapy / Q000473:pathology*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000473:pathology*; D055815:Young Adult
chemical_list: D000962:Antimalarials; D006454:Hemoglobins