The proportion of birth asphyxia associated with maternal heart rate artifact during electronic fetal monitoring in labor

Abstract

Objective: To estimate the proportion of birth asphyxia cases associated with delay in delivery (DD) due to maternal heart rate artifact (MHRA).

Methods: Retrospective review of Canadian Medical Protective Association closed medico-legal cases of birth asphyxia from 2011-2020 in term labor, leading to hypoxic ischemic encephalopathy, cerebral palsy or stillbirth. The final two hours of electronic fetal monitoring (EFM) were analyzed in 10-minute time epochs by three independent experts using a template for evidence of MHRA judged to have resulted in DD. Records were also assessed for EFM classification, documentation of maternal pulse / MHRA and labor factors.

Results: Thirty-four cases of birth asphyxia were identified. Thirteen cases (38%) were found to have DD due to MHRA of which 9 (69%) were in the second stage of labor. The average estimated DD was 44.2 minutes +21.9. There was a lower proportion of time epochs with abnormal EFM in the 13 cases with DD versus 21 cases without DD [14.7% vs. 47.3%, (OR 0.19 (0.11-0.33) P < 0.002)]. Conversely, there was a higher proportion of MHRA [62.9% vs. 5.4%, (OR 29.8 (15.5-57.3) P = 0.002)]. The maternal pulse was documented in 34% vs. 30% respectively. Chart review revealed no recognition by the caregivers of the occurrence of MHRA.

Conclusion: Unrecognized MHRA resulting in a falsely reassuring fetal heart rate, mainly in the active second stage, led to DD in more than one third of birth asphyxia cases. These outcomes may be preventable by education and the routine use of technologies to detect MHRA.

Keywords: Artifacts; Labor; Obstetric; asphyxia neonatorum; fetal monitoring.