Umbilical arterial blood lactate as predictor of early neonatal outcome and evaluation of intrapartum asphyxia

Abstract

Background: Perinatal asphyxia is a leading cause of under-5 mortality and exerts great pressure on the health system. Adequate foetal monitoring in labour is paramount in the early detection of foetal distress to prevent perinatal asphyxia. Several methods of foetal monitoring are in use with varying efficacy. This study investigated the efficacy of umbilical arterial (UA) lactate assay in predicting adverse perinatal outcomes.

Methodology: This was a prospective longitudinal study involving 160 pregnant women in the active phase of labour at term who met the inclusion criteria. They were recruited using a consecutive sampling technique and underwent a cardiotocography. Then they were classified into normal and abnormal cardiotocographic groups. At delivery, the UA blood of all of the babies was collected and assayed for serum lactate, and the levels were correlated with the perinatal outcome. The perinatal outcomes were measured by Apgar scores, admission into the neonatal unit, and hypoxic ischaemic encephalopathy. Analysis was done to determine the sensitivity and specificity of UA lactate in predicting birth asphyxia, hypoxic ischaemic encephalopathy, and neonatal unit admission.

Results: The mean age ± standard deviation (SD) between the two cardiotocography (CTG) groups, normal years (30.55 ± 5.59) and abnormal years (29.86 ± 5.51), were similar. A critical UA lactate concentration > 9.1 mmol/L predicted Apgar scores < 7 at 5 min with a sensitivity and specificity of 76.47% (CI: 50.1-93.2) and 91.55% (CI: 85.7-95.6%), respectively. Also, the need for neonatal unit admission was predicted at a cut-off point >9.1 mmol/L with a sensitivity of 61.90% (CI: 38.4-81.9) and specificity of 91.30% (CI: 85.3-95.4). Umbilical artery lactate levels > 11.2 mmol/L predicted the development of hypoxic ischaemic encephalopathy in neonates with a sensitivity of 100% (CI: 39.8-100.0) and specificity of 88.39% (CI: 82.3-93.0).

Conclusion: Umbilical artery lactate correlates with adverse pregnancy outcomes and is an excellent tool for predicting adverse neonatal outcome.

Keywords: Apgar scores; Hypoxic ischaemic encephalopathy; Intrapartum monitoring; Perinatal outcome; Umbilical arterial blood lactate.

Figure 1

ROC curve of serum lactate level in predicting APGAR score <7 at 5 min. AUC: 0.908; 95% CI: 0.852–0.948; p < 0.001.

Figure 2

ROC curve of serum lactate level in predicting neonatal admission. AUC: 0.908; 95% CI: 0.852–0.948; p < 0.001.

Figure 3

ROC curve of serum lactate level in predicting HIE. AUC: 0.960; 95% CI: 0.917–0.984; p < 0.001.