Haemoglobin measurement using three different techniques in women undergoing planned vaginal birth

All participants will have an intravenous cannula (IVC) inserted and a venous blood sample taken as part of their routine management of labour. The timing of the IVC and venous blood sampling will be when the woman requires an IVC during her labour as part of routine management of labour. This blood will be sent to the laboratory for the laboratory haemoglobin measurement and, at the same time as the venous blood is sampled and from that same sample, one drop of blood will be used to obtain the Hemocue® haemoglobin sample measurement. A HemoCue® measurement of haemoglobin will also be taken at the same time via a finger prick (like a blood glucose finger prick test). At the same time blood is taken for laboratory haemoglobin measurement and Hemocue®, the finger probe of the Rad-67 continuous haemoglobin monitor will be applied to the participant finger or thumb on the same arm as the blood is taken from. The Rad-67 device obtains the haemoglobin via the placement of a finger/thumb probe that rests comfortably on a finger/thumb. The first haemoglobin reading from the Rad-67 device will be recorded as the haemoglobin result from that device. Staff taking blood samples: one of the study investigators will take the blood samples Timing of blood samples: samples will all be taken at the same time either at the start or during labour when the IVC is inserted - only one sample at one time using each method will be undertaken Location of blood samples: blood samples will all be taken from the participant's arm or hand, and the location within the hospital will be one of the acute care areas - birthing suite, emergency department, assessment centre - or wherever the participant has an IVC inserted