Use of fetal scalp blood lactate for assessing fetal well-being during labour

A fetal heart rate that is abnormal or not reassuring during labour may be caused by the inability of the baby to adapt to decreases in oxygen supply during the birth. Inadequate oxygen supply may lead to the development of acidosis (low pH levels) and increased lactate in the blood. After the amniotic membranes have ruptured and the cervix dilated to around 3 cm, it is possible to measure lactate (or pH) levels in a sample of blood taken from the baby's scalp. A much smaller amount of blood is needed for the lactate test than to measure pH. This review identified two studies of 3348 mother-baby pairs that compared lactate and pH testing in labour. Lactate testing was more likely to be successful than pH testing, but with no differences in newborn outcomes, including the number of babies with low Apgar scores, low pH in their cord blood or admissions to the neonatal intensive care nursery. There were no differences in the number of mothers having caesarean sections, forceps or vacuum births between the two groups. We conclude that lactate testing in labour may be more likely to be successfully achieved than pH testing.