Lactate measurements have become increasingly preferred over pH analysis in the evaluation of fetal acidaemia in labour. In a busy labour ward, often the umbilical cord may be sampled late and as a result yield unreliable lactate values.

To investigate the agreement of hand‐held device Lactate Pro with a reference method blood gas analyser and evaluate the stability of umbilical cord lactate values over time.

Prospective study carried out at elective caesarean section. Sixteen umbilical cords were double clamped immediately after delivery with paired arterial and venous blood samples collected by an independent researcher, at varying time intervals, and processed by two Lactate Pro devices and a reference method blood gas analyser.

A significant difference of −0.41 to 0.10 mmol/L was found when different groups of Lactate Pro devices were compared with blood gas analyser at lactate values up to 5.70 mmol/L, with average lactate value of 2.45 mmol/L. Over time, there is progressive rise in lactate samples obtained from the umbilical cord.

Lactate Pro devices have a significant difference, but when used in clinical practice on cord blood after delivery, this is unlikely to be meaningful. In intrapartum fetal surveillance, a systematic overestimation might lead to unnecessary intervention. It is possible to retrospectively predict the likely level of lactate at birth in delayed cord samples.