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Review
. 2022 Nov;129(12):2070-2081.
doi: 10.1111/1471-0528.17234. Epub 2022 Jun 5.

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies

Mikko J Tarvonen  1 , Christopher A Lear  2 , Sture Andersson  3 , Alistair J Gunn  2 , Kari A Teramo  1
Affiliations
Review

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies

Mikko J Tarvonen et al. BJOG. 2022 Nov.

Abstract

Increased fetal heart rate variability (FHRV) in intrapartum cardiotocographic recording has been variably defined and poorly understood, limiting its clinical utility. Both preclinical (animal) and clinical (human) evidence support that increased FHRV is observed in the early stage of intrapartum fetal hypoxaemia but can also be observed in a subset of fetuses during the preterminal stage of repeated hypoxaemia. This review of available evidence provides data and expert opinion on the pathophysiology of increased FHRV, its clinical significance and a stepwise approach regarding the management of this pattern, and propose recommendations for standardisation of related terminology.

Keywords: ZigZag pattern; acidaemia; cardiotocography; electronic fetal monitoring; fetal heart rate; increased variability; marked variability; neonatal morbidity; pregnancy; saltatory pattern.

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Conflict of interest statement

Open access funding provided by University of Helsinki including Helsinki University Central Hospital. Mikko Tarvonen has received support from the Foundation for Paediatric Research, Finska Läkaresällskapet and Olga & Vilho Linnamo Foundation. Sture Andersson has received grants from a Special Governmental Subsidy for Clinical Research, Finska Läkaresällskapet, and the Society for Paediatric Research in Finland. Christopher Lear and Alistair Gunn received funding for this review from the Health Research Council of New Zealand. The sponsors had no role in the study design; collection, analysis, or interpretation of data, writing of the report, or in the decision to submit the report for publication. The authors have no interests to declare. Completed disclosure of interest forms are available to view online as supporting information.

Figures

FIGURE 1
FIGURE 1
Intrapartum CTG recording at 41+0 weeks of pregnancy. Upper trace: Normal baseline FHR (135 bpm) followed by three increased FHRV episodes with durations of 6–7 minutes. Note the varying frequency of uterine contraction, with the periods of increased FHRV associated with greater contraction frequency, with resolution during periods of reduced contraction frequency. These changes are further followed by increased FHR, reduced FHRV and late decelerations. Lower trace: The same fetus with repeated interdeceleration increased FHRV patterns followed by unstable baseline FHR. A male fetus was born vaginally spontaneously at the end of the tracing. Umbilical cord blood gas analysis at birth showed deep acidaemia, UA pH 6.95, UA BE −15.4 and UV pH 7.04, UV BE −12.1. FHR was recorded via fetal scalp electrode with paper speed 1 cm/min. BE, base excess; bpm, beats per minute; CTG, cardiotocography; FHR, fetal heart rate; FHRV, fetal heart rate variability; UA, umbilical artery; UV, umbilical vein
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