[Correlation between fetal scalp samples and umbilical cord samples]

The objective was to evaluate the correlation between fetal scalp base excess (BE) and umbilical cord BE. Respective value of fetal scalp pH, BE and lactate for the prediction of neonatal metabolic acidosis were also evaluated.

A retrospective monocentric study was conducted in a French tertiary care academic maternity. All the patients who had a fetal scalp sampling during labor in 2010, less than 90 minutes before delivery were included. Fetal heart rate abnormalities (FHRA) were classified by degree of severity, according to the French guidelines. The differences between fetal scalp samples and umbilical cord samples over time and in relation with the type of FHRA were analyzed for pH and BE. The differences between fetal scalp pH and cord pH over time and in relation with scalp BE were analyzed. The correlation between fetal scalp samples and cord samples for pH, BE and lactate was estimated. Receiver operating characteristics (ROC) curves for fetal scalp pH, lactate and BE to predict umbilical cord pH under 7.20 were calculated.

Seventy-one cases were included. The difference between fetal scalp sample and cord sample was lower when the sample was made closest to delivery both for pH and BE. The gravity of FHRA was not predictive of a faster decrease of pH or BE over time. The correlation was significant for pH (r=0.23, p=0.03) between scalp samples and cord samples, as for BE (r=0.49, p=0.001) and lactate (r=0.52, p=0.001). The ROC curves for pH, BE and lactate displayed a similar pattern.

Fetal scalp and umbilical cord samples, for pH, BE and lactate were significantly correlated but their respective predictive value for cord pH less or equal to 7.20 was poor.