Defining peri-operative anaemia in pregnant women – challenging the status quo

Abstract

Peri-operative anaemia is a significant risk factor for morbidity and mortality. Anaemia during pregnancy is associated with adverse maternal and neonatal outcomes, and postpartum haemorrhage remains a leading cause of maternal mortality worldwide. Caesarean section is an operation incurring moderate risk of bleeding, and rates are rising globally. Recent international consensus guidelines recommend targeting a pre-operative haemoglobin > 130 g.l-1 for all patients having surgery with moderate-to-high risk of bleeding, regardless of sex. It is unclear how this recommendation translates to pregnant women, where anaemia is defined at a much lower haemoglobin level of < 110 g.l-1 . Long-standing definitions of anaemia during pregnancy are likely to be the result of flawed sampling of a so-called 'normal' but anaemic female population, given the high prevalence of iron deficiency and anaemia in healthy menstruating women. Contemporary data suggest that haemoglobin values in iron-replete pregnant women are higher than previously thought. The definition of anaemia has significant clinical implications, particularly for peri-operative management of women undergoing caesarean section. In addition, we should differentiate between lower reference values and optimal haemoglobin targets. The haemoglobin level associated with optimal obstetric and neonatal outcomes requires further investigation in pregnant women.