Outcome of severe intrapartum acidemia diagnosed with fetal scalp blood sampling

To analyze short-term neonatal outcome and the sampling to delivery interval in cases with severe intrapartum acidemia diagnosed with fetal scalp blood sampling (FBS).

This is a secondary analysis of data from a trial of 2992 women, who were, when indicated, randomized to either lactate or pH analyses by FBS. Median and 95(th) centile values for lactate analyses were 2.9 mmol/L and 6.6 mmol/L, respectively. Corresponding pH values were 7.30 and 7.17. We defined severe intrapartum acidemia as lactate >6.6 mmol/L or pH <7.17. Outcome measures were cord artery pH <7.00, Apgar <7 at 5 min, hypoxic ischemic encephalopathy and time interval from FBS to delivery.

Severe intrapartum acidemia was present in 85/1355 (6.3%) cases with lactate analyses and in 69/1008 (6.8%) cases with pH analyses. Cord artery pH <7.00 occurred in 12/154 (7.8%), Apgar <7 at 5 min in 16/154 (10.4%) and hypoxic ischemic encephalopathy in 4/154 (2.6%) of the cases. There were no differences in outcomes between the two groups. However, delivery was expedited more rapidly in the pH management group (median 16 vs. 21 min; P=0.01).

Severe neonatal morbidity occurred in 10% or less in this high-risk group. FBS is an early marker of intrapartum hypoxia and can be used to prevent severe birth acidemia. Lactate might be an earlier marker than pH in the hypoxic process.