RESUMEN
The effect of anaemia [haemoglobin <11 g/dl] during pregnancy on preterm delivery was prospectively studied in 921 low-risk pregnancies. The association between anaemia and prematurity was measured at three different haemoglobin levels, early in pregnancy and during the third trimester. The risk of prematurity was higher with haemoglobin <9 g/dl in early pregnancy, followed by haemoglobin <10 g/dl during the same period; the least risk was recorded during the third trimester when haemoglobin was <10 g/dl. In multivariate logistic regression analysis, haemoglobin was the most important predictor of prematurity after controlling for other confounders. When applying the logistic predictive equation, a woman with all the significant risk factors included in the multivariate analysis had a 72% probability of giving birth to a preterm baby