Pre-caesarean section haemoglobin: A worthless investigation

Haemoglobin concentration is measured routinely before caesarean section in many obstetric units. It is also measured early in the third trimester in order to screen for anaemia. We investigated the hypothesis that when the haemoglobin concentration was normal in the early third trimester, a repeat measurement immediately before surgery at term provided no useful additional information. A total of 106 cases were studied of elective (n = 45) and emergency (n = 61) caesarean sections. In the majority of elective (28 of 45) and emergency (49 of 61) patients, the haemoglobin concentration rose by term. In a minority of elective (14 of 45) and emergency (12 of 61) patients, the haemoglobin concentration fell. The largest fall was by 1.3 g/dl and the lowest term value was 10.1 g/dl. In three elective patients, the concentration did not change. Peri-operative management at term may therefore be guided by the haemoglobin concentration measured early in the third trimester. There appears to be no clinically significant change in haemoglobin during this time and there are physiological changes in the circulation that explain this effect. Discontinuation of routine pre-operative haemoglobin concentration measurement could lead to a significant financial saving.