Monitoring Fetal Electroencephalogram Intrapartum: A Systematic Literature Review

Abstract

Background: Studies about the feasibility of monitoring fetal electroencephalogram (fEEG) during labor began in the early 1940s. By the 1970s, clear diagnostic and prognostic benefits from intrapartum fEEG monitoring were reported, but until today, this monitoring technology has remained a curiosity. Objectives: Our goal was to review the studies reporting the use of fEEG including the insights from interpreting fEEG patterns in response to uterine contractions during labor. We also used the most relevant information gathered from clinical studies to provide recommendations for enrollment in the unique environment of a labor and delivery unit. Data Sources: PubMed. Eligibility Criteria: The search strategy was: ("fetus"[MeSH Terms] OR "fetus"[All Fields] OR "fetal"[All Fields]) AND ("electroencephalography"[MeSH Terms] OR "electroencephalography"[All Fields] OR "eeg"[All Fields]) AND (Clinical Trial[ptyp] AND "humans"[MeSH Terms]). Because the landscape of fEEG research has been international, we included studies in English, French, German, and Russian. Results: From 256 screened studies, 40 studies were ultimately included in the qualitative analysis. We summarize and report features of fEEG which clearly show its potential to act as a direct biomarker of fetal brain health during delivery, ancillary to fetal heart rate monitoring. However, clinical prospective studies are needed to further establish the utility of fEEG monitoring intrapartum. We identified clinical study designs likely to succeed in bringing this intrapartum monitoring modality to the bedside. Limitations: Despite 80 years of studies in clinical cohorts and animal models, the field of research on intrapartum fEEG is still nascent and shows great promise to augment the currently practiced electronic fetal monitoring. Prospero Number: CRD42020147474.

Keywords: EEG; electrocorticogram; fetus; infant; labor; magnetoencephalogram; neonates.

Figure 1

PRISMA flow diagram summarizing the study selection process and the number of studies ultimately deemed eligible to be included in the meta-analysis.

Figure 2

(A) Simultaneous recording of fECG and fEEG. Artifacts from fECG effect on fEEG can be identified by recording both traces simultaneously. From Hopp et al. (44). (B) Intra and post-partum fetal/neonatal EEG recordings showing the great similarity between both traces. From Hopp et al. (44). EEG, electroencephalogram. (C) Cardiotocogram (top) and fEEG (bottom) recorded during early cardiac deceleration. The fEEG pattern represents the change during contractions with high amplitude low-frequency waves and the recovery once the contractions ceased. From Hopp et al. (44). fEEG, fetal electroencephalogram. (D) Simultaneous recording of fECG (top trace), two-channel fEEG (middle two traces), and FHR (bottom trace). This figure shows fEEG changes during severe variable deceleration. The fEEG trace shows waves of low amplitude and near isoelectricity as well as intermittent spike potentials between contractions. From Hopp et al. (30). fECG, fetal electrocardiogram; fEEG, fetal electroencephalogram; FHR, fetal heart rate.

Figure 3

Emergence of EEG-FHR pattern in a fetal sheep model. A representative 10 min recording made during the early stage of severe umbilical cord occlusions (UCOs) at a pH of about 7.2 and about 60 min prior to pH dropping to <7.00 indicated cardiovascular decompensation (hypotensive fetal systemic arterial blood pressure; ABP) in response to FHR deceleration triggered by UCO. It shows the pathognomonic fEEG pattern (black bar = 2.5 min). Red arrows indicate the pathognomonic burst-like EEG activity correlated in time to the FHR decelerations and pathological ABP decreases during the UCOs. UCOs continued until pH < 7.00 was reached in each fetus (about 4 h). Fetal arterial blood samples were taken each 20 min. This timing corresponds to pH of 7.20 seen in 20% of births (62). From Wang et al. (57) EEG, electroencephalogram, μV; ECoG, electrocorticogram, μV; ABP, fetal systemic arterial blood pressure, mmHg; FHR, fetal heart rate, bpm; UCOs, umbilical cord occlusions, mmHg (rise in occlusion pressure corresponds to an UCO).

Figure 4

FEEG recording from the standard fetal scalp electrode during the first stage of labor. A period of 10 min is shown with fEEG tracing (bottom) filtered 0.5–12 Hz and the corresponding power spectral analysis (top left) and wavelet transform (top left) to demonstrate the time-frequency behavior of fEEG. Note switching between delta and alpha-band activity. The X-axis shows time, with each segment corresponding to 0.5 min for a total of 10 min. Signal processing was performed in EEGLAB using Matlab 2013b, MathWorks, Mattick, MA. fEEG: fetal electroencephalogram.

Figure 5

Suggested study protocol. Fetal EEG recording during labor will be followed by cord blood measurements at birth to determine the degree of acidemia and the neonatal morbidity score. FSE, fetal scalp electrode; EEG, electroencephalogram; HR, heart rate.