To estimate the frequency of anaemia in pregnant women before and after the fortification of flours with Fe.

Retrospective study developed from secondary data obtained from medical records.

Two health units in Rio de Janeiro, Brazil.

Socio-economic, demographic, obstetric and Hb concentration data were collected of 778 pregnant women attending prenatal care. Two study groups were created: the first referred to the period before fortification (G1, n 391), including women whose parturition happened before June 2004; and the second referred to the period after fortification (G2, n 387), including women whose last menstrual cycle happened after June 2005. The Hb cut-off point adopted for anaemia diagnosis was <11·0 g/dl.

In linear regression models, when Hb concentration was expressed as a dependent variable, women in G2 presented Hb concentration 0·26 g/dl and 0·36 g/dl higher during the second and third trimesters of pregnancy, respectively, compared with G1. In logistic regression models where the dependent variable was anaemia during the second and third trimesters, it was verified that being a member of G2 was a protective factor against anaemia in the third trimester. Regarding the presence of anaemia at any gestational moment, it was verified that being a member of G2 represented a protective factor against anaemia during pregnancy.

Results indicate the protective effect of the fortification of flours with Fe in the fight against gestational anaemia, contributing to prevention and control of this nutritional disorder among pregnant women.