Heart rate variability as a biomarker for autonomic recovery and maternal wellbeing following caesarean delivery: a scoping review protocol

Abstract

Introduction

Caesarean delivery accounts for more than 21% of all births worldwide, with rates exceeding 30% in several countries, yet objective physiological markers for monitoring postoperative maternal recovery remain scarce. Heart rate variability (HRV), a non-invasive index of autonomic nervous system integrity, has demonstrated prognostic value in general surgical populations. This scoping review will map the extent, range and nature of evidence on HRV monitoring in caesarean populations within a recovery-assessment framework.

Methods and analysis

The review follows a Population–Concept–Context framework. The primary population comprises women undergoing elective caesarean delivery, with emergency procedures analysed as a distinct subgroup. The concept covers any validated measurement of HRV parameters (time-domain, frequency-domain and non-linear indices). The context spans the perioperative-to-postpartum continuum, from preoperative baseline through 6 weeks after delivery. Adhering to the Joanna Briggs Institute methodology, we will employ a three-step search strategy across PubMed, Embase, CINAHL, Cochrane Central Register of Controlled Trials and Web of Science. Two independent reviewers will screen records and extract data. Findings will be synthesised narratively and presented via temporal evidence mapping, an evidence gap map, and structured summary tables.

Ethics and dissemination

Formal ethics approval is not required because this review exclusively analyses published data. We will disseminate our findings through publication in a peer-reviewed journal and presentations at relevant academic conferences.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This scoping review protocol follows the rigorous Joanna Briggs Institute methodology and adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) reporting guidelines to ensure systematicity and transparency.

• The search strategy is comprehensive, covering major medical databases (PubMed, Embase, CINAHL, Cochrane Library and Web of Science) to capture a wide range of evidence.

• The use of a three-tiered analytic framework for heart rate variability parameters allows for a nuanced synthesis of established and emerging autonomic biomarkers.

• Temporal evidence mapping will be employed to visually identify research gaps across the perioperative-to-postpartum continuum.

• A limitation of this study is the exclusion of non-English publications, which may introduce language bias and omit relevant data from specific geographic regions.

Introduction

Caesarean delivery ranks among the most frequently performed surgical procedures worldwide. The global caesarean rate reached 21.1% in 2018, with projections indicating a rise to 28.5% by 2030.^{1 2} In several countries, including China and Brazil, rates already surpass 30–50%, reflecting both medical and non-medical drivers of surgical birth.² Although perioperative safety has improved substantially over recent decades, the tools available for monitoring maternal recovery after caesarean delivery remain limited. Standard postoperative assessments typically rely on clinical milestones such as time to first ambulation, resumption of oral intake and subjective pain ratings. While these measures are practical, they capture only surface-level indicators and fail to reflect the underlying physiological processes governing recovery.

The autonomic nervous system (ANS) occupies a central role in surgical recovery. Through its two principal branches—the sympathetic division, which mediates the acute stress response, and the parasympathetic division, dominated by vagal efferent pathways that promote restoration and homeostasis, the ANS coordinates haemodynamic stability, gastrointestinal motility, immune regulation and wound healing.³ Vagal tone, in particular, exerts anti-inflammatory effects through the cholinergic anti-inflammatory pathway, whereby acetylcholine released at the splenic nerve terminus attenuates pro-inflammatory cytokine production by macrophages.⁴ The balance between sympathetic activation and parasympathetic recovery therefore represents a plausible mechanistic pathway linking ANS function to postoperative outcomes.

Heart rate variability (HRV) provides a non-invasive, quantitative window into ANS regulation. By analysing the beat-to-beat fluctuations in R–R intervals, HRV decomposes autonomic input to the sinoatrial node into measurable components. Time-domain indices such as the root mean square of successive differences (RMSSD) predominantly reflect vagal modulation, while frequency-domain measures including high-frequency (HF) power map respiratory-linked parasympathetic activity, and the ratio of low-frequency to HF power (LF/HF) has been interpreted as an index of sympathovagal balance, though this interpretation remains debated.^{3 5} In 1996, a joint Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology published standards for HRV measurement, physiological interpretation and clinical application, which continue to serve as the methodological reference for study design and reporting.³

From a translational perspective, HRV offers a unique bridge between basic autonomic neurobiology, such as the cholinergic anti-inflammatory pathway, and bedside clinical outcomes. Tracking these autonomic shifts in real-time could eventually allow clinicians to identify patients who are deviating from normal recovery trajectories, paving the way for personalised, targeted interventions within Enhanced Recovery After Caesarean (ERAC) protocols.

In general surgical populations, the prognostic value of preoperative HRV has attracted considerable interest. Frandsen and colleagues conducted a systematic review of 63 studies. Because of significant methodological heterogeneity across the included literature, they could not perform a meta-analysis. However, their narrative synthesis suggested that reduced preoperative HRV was generally associated with a higher incidence of perioperative complications, including cardiac arrhythmias, pulmonary infections and postoperative delirium.⁶ The underlying mechanism likely involves attenuated vagal anti-inflammatory capacity, rendering patients with low HRV less able to mount an appropriate homeostatic response to surgical stress. Importantly, Frandsen’s review adopted a predictive paradigm: it examined whether a single preoperative HRV measurement could forecast subsequent complications. This is conceptually distinct from using serial HRV measurements to track recovery over time.

Within obstetric anaesthesia, HRV research has focused almost exclusively on haemodynamic prediction. Hanss and colleagues demonstrated in 2005 that the preoperative LF/HF ratio could predict the severity of spinal anaesthesia-induced hypotension during elective caesarean delivery,⁷ and subsequently showed in 2006 that HRV-guided prophylactic vasopressor administration could attenuate this complication.⁸ Yu and colleagues synthesised the prediction literature in a systematic review.⁹ These studies share a common orientation: they treat HRV as a static, single-timepoint predictor of an intraoperative event. No published review has examined HRV as a dynamic, longitudinal marker of postoperative autonomic and functional recovery following caesarean delivery.

This distinction between prediction and assessment is methodologically consequential. A biomarker with strong predictive validity for complications does not necessarily exhibit sensitivity to recovery trajectories; the statistical frameworks, measurement intervals and analytic strategies differ between the two applications. A scoping review restricted to the recovery-assessment paradigm is therefore warranted as a discrete scholarly contribution rather than an extension of existing predictive reviews.

The clinical relevance of this gap is amplified by the growing adoption of ERAC protocols, which aim to accelerate maternal functional recovery through multimodal interventions spanning preoperative counselling, intraoperative technique and postoperative care.^{10 11} Despite their increasing implementation, ERAC programmes rely predominantly on patient-reported outcome measures (eg, the Obstetric Quality of Recovery-11 score) and clinician-assessed milestones.¹² An objective physiological biomarker capable of reflecting real-time autonomic restoration would provide a complementary dimension for evaluating ERAC effectiveness, identifying patients with delayed recovery and tailoring postoperative interventions.

Pregnancy itself substantially alters ANS function. Resting heart rate increases progressively, while HRV indices decline, reflecting the haemodynamic and neurohumoral adaptations required to support placental perfusion.¹³ Sarhaddi and colleagues, using continuous wearable monitoring in 58 women, reported that HRV remained depressed relative to pre-pregnancy values at 3 months postpartum.¹⁴ Whether caesarean delivery imposes an additional or prolonged autonomic burden relative to vaginal birth, and whether the magnitude of postoperative HRV depression correlates with functional recovery, remain open questions that fall within the scope of the present review. A recent scoping review by Byfield et al mapped the use of wearable HRV devices across the general perinatal period, focusing heavily on mental health and stress.¹⁵ While their work confirms the feasibility of postpartum HRV tracking, our review specifically isolates the caesarean delivery population. We are applying a surgical recovery lens—rather than a psychological one—to see if HRV can serve as a physiological marker for acute and subacute autonomic restoration and align with ERAC pathways.

A preliminary search of PROSPERO, the Cochrane Database of Systematic Reviews, Joanna Briggs Institute (JBI) Evidence Synthesis and PubMed was conducted in January 2026. No existing or registered review was identified that maps the use of HRV for recovery assessment after caesarean delivery. Given the concurrent emergence of consumer-grade wearable HRV monitors and the expansion of ERAC programmes, a systematic mapping of the available evidence is both timely and necessary.

The aim of this scoping review is to identify, characterise and map the published evidence on HRV monitoring in relation to autonomic recovery and maternal well-being following caesarean delivery. The review will delineate the parameters measured, the time points examined, the methodological approaches employed and the outcomes investigated, thereby revealing research gaps and informing the design of future interventional studies.

Review question

The primary review question is: What is the nature, extent and distribution of published evidence on the use of heart rate variability for evaluating autonomic recovery and maternal well-being after caesarean delivery?

The following secondary questions will guide data extraction and synthesis:

1. Which HRV parameters (time-domain, frequency-domain, non-linear or proprietary indices) have been measured in caesarean populations, and what recording methodologies and devices have been employed?

2. What clinical outcomes have been examined in conjunction with HRV, and what associations or correlations have been reported?

3. At what time points relative to surgery have HRV measurements been obtained, and do longitudinal patterns of autonomic change emerge from the literature?

4. What methodological limitations, sources of heterogeneity and evidence gaps characterise the existing literature?

Eligibility Criteria

The eligibility criteria for this scoping review are structured according to the Population–Concept–Context framework, as summarised in table 1.

Table 1. PCC framework for eligibility criteria.

Element	Inclusion criteria	Analytic approach
Population	Primary: elective caesarean (any indication, gestational age, parity, anaesthetic technique). Secondary: emergency caesarean.	Emergency caesarean analysed as a distinct subgroup. High-risk comorbidities flagged for sensitivity analysis.
Concept	Primary tier: RMSSD, HF power. Secondary tier: SDNN, LF, LF/HF. Tertiary tier: proprietary indices (ANI, etc.).	Primary tier parameters form main analysis. Tertiary tier reported descriptively only.
Context	Preoperative baseline (including day-of-surgery), intraoperative, postoperative through 6 weeks postpartum.	Baseline timing (>24 hour vs <24 hour) as stratification variable. Intraoperative data analysed separately.

ANI, Analgesia Nociception Index; HF, high frequency; LF, low frequency; PCC, Population Concept Context; RMSSD, root mean square of successive differences; SDNN, SD of normal-to-normal intervals.

Population

The primary population comprises women undergoing elective (scheduled) caesarean delivery, irrespective of indication, gestational age, parity or anaesthetic technique (spinal, epidural or combined spinal-epidural). Studies enrolling women undergoing emergency or unplanned caesarean delivery will be included but subjected to separate subgroup analysis, given the distinct physiological context of emergency surgery: prolonged labour, fetal distress, acute maternal anxiety and catecholamine surges may independently alter baseline sympathovagal balance and confound recovery trajectories. Studies exclusively examining vaginal delivery without a caesarean comparator will be excluded.

Concept

The central concept is heart rate variability, assessed by any validated method of R–R interval analysis. To facilitate synthesis, HRV parameters will be organised into three analytic tiers. The primary tier includes RMSSD and HF power, which are established markers of cardiac vagal modulation with a direct mechanistic link to anti-inflammatory capacity.^{3 4} The secondary tier encompasses SDNN (reflecting overall autonomic variability), LF power and the LF/HF ratio. The tertiary tier comprises proprietary or commercially derived indices, such as the Analgesia Nociception Index or other device-specific composites; these will be reported descriptively but will not be aggregated with standard parameters due to limited comparability. Studies reporting only mean heart rate without any index of variability will be excluded.

Context

The temporal context spans from the preoperative baseline through 6 weeks postpartum, encompassing the conventional puerperal period. Preoperative baseline measurements include those obtained on the day of surgery prior to anaesthesia induction; however, the proximity of such measurements to the surgical event introduces potential confounding from anticipatory anxiety. We will therefore record whether the baseline was obtained more than 24 hours or less than 24 hours before surgery and examine baseline timing as a stratification variable in the subgroup analysis. Intraoperative HRV measurements will be included but analysed separately, given the direct pharmacological effects of neuraxial and general anaesthesia on autonomic indices. For postoperative monitoring, we will extract data across specific recovery windows: the immediate postoperative phase (eg, within the post-anaesthesia care unit), early recovery (24–48 hours post-surgery), at hospital discharge, and the late puerperal phase (up to 6 weeks postpartum). To provide a complete map of the existing literature, we will also include studies that use HRV purely to predict intraoperative events (such as spinal anaesthesia-induced hypotension) even if they lack postoperative follow-up. However, during data synthesis, these purely predictive studies will be distinctly categorised and analysed separately from those focusing on longitudinal postoperative recovery.

Types of sources

Original research published in peer-reviewed journals will be eligible, including randomised controlled trials, prospective and retrospective cohort studies, case-control studies and cross-sectional studies. Conference abstracts and dissertations will be excluded owing to insufficient methodological detail for meaningful data extraction. Narrative and systematic reviews will be excluded from direct analysis, but their reference lists will be hand-searched to identify additional primary studies. Publications not available in English will be excluded; this pragmatic decision reflects the language competencies of the review team and will be acknowledged as a limitation.

Methods

This scoping review protocol was developed in accordance with the JBI methodology for the conduct of scoping reviews, as updated by Peters and colleagues.¹⁶ Reporting will adhere to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR).¹⁷ The completed PRISMA-ScR checklist is provided as a supplementary file. The protocol will be prospectively registered on the Open Science Framework (OSF) prior to formal database searching.

Search strategy

The search strategy follows the JBI-recommended three-step approach. In the first step, an initial limited search of PubMed was conducted to identify relevant articles and analyse the index terms and text words contained in titles and abstracts. In the second step, a comprehensive search strategy was developed using all identified keywords and index terms and adapted for each database. The full PubMed strategy is presented in online supplemental file 1). In the third step, the reference lists of all included studies will be hand-searched to identify any additional sources not captured by the electronic search.

The search combines three conceptual blocks: (a) heart rate variability and ANS function; (b) caesarean delivery; and (c) postoperative recovery and enhanced recovery contexts. The databases to be searched are PubMed (including MEDLINE), Embase (via Ovid), CINAHL (via EBSCOhost), the Cochrane Central Register of Controlled Trials (CENTRAL) and Web of Science Core Collection. No date limits will be imposed to ensure comprehensive capture. The search is scheduled for March 2026 and will be updated prior to manuscript submission if more than 6 months have elapsed.

Study selection

All retrieved records will be imported into Rayyan (Qatar Computing Research Institute) for deduplication and screening management. Two reviewers will independently screen titles and abstracts against the eligibility criteria. Records deemed potentially eligible by either reviewer will proceed to full-text assessment. Full texts will be independently evaluated by both reviewers, with reasons for exclusion documented at this stage. Disagreements at any stage will first be discussed between the two primary reviewers. If they cannot reach a consensus, a third reviewer will step in to independently assess the article against the predefined eligibility criteria. If a disagreement still remains after this third assessment, the entire review team will hold a consensus meeting to make a final, unanimous decision. The selection process will be reported in a PRISMA flow diagram (figure 1).

Figure 1. PRISMA 2020 flow diagram for the scoping review process. Note: This is a template; actual numbers of screened and included studies will be populated on completion of the search. HRV, heart rate variability; PONV, postoperative nausea and vomiting; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

To ensure consistency in the application of eligibility criteria, a calibration exercise will precede formal screening. Both reviewers will independently screen a random sample of 50 titles and abstracts, followed by a consensus meeting to discuss discrepancies. Inter-rater reliability will be assessed using Cohen’s kappa statistic; a threshold of ≥0.70 is required before proceeding. Should reliability fall below this threshold, the eligibility criteria will be refined and the calibration repeated.

Data extraction

Data will be extracted using a standardised form designed specifically for this review (online supplemental file 2). The form will be pilot-tested on five included studies and revised as necessary before full extraction. Data extraction will be performed by one reviewer and independently verified by a second reviewer. Discrepancies will be resolved through discussion. Where critical data are missing or ambiguous, corresponding authors will be contacted by email, with a maximum of two contact attempts over a 4-week period.

The extraction form captures the following domains: study characteristics (first author, year, country, journal, funding source, study design); participant characteristics (sample size, age, gestational age, elective versus emergency caesarean, anaesthetic technique, relevant comorbidities); HRV measurement methodology (recording device, recording duration, sampling rate, R-R interval editing techniques, artefact correction methods, specific mathematical algorithms or software used for HRV calculation, and reported compliance with the 1996 Task Force standards); measurement timing (preoperative baseline with classification as >24 hour or <24 hour before surgery, intraoperative, immediate postoperative, days 1–2, discharge, 2 weeks, 6 weeks; single vs serial measurements); confounding factor documentation (maternal position during recording, controlled breathing protocols, breastfeeding status, concurrent pain scores, analgesic or anxiolytic medications); HRV parameters reported (categorised by tier); clinical outcomes examined; principal findings (including effect sizes, CIs, p values, receiver operating characteristic data and correlation coefficients); and author-reported limitations.

Critical appraisal

Consistent with established JBI scoping review methodology, formal critical appraisal of included studies is not mandated.¹⁶ However, given that the methodological quality of HRV research is a central concern of this review, particularly with respect to adherence to the 1996 Task Force standards for measurement and reporting, we will incorporate a structured quality annotation within the data extraction process. Specifically, each included study will be classified according to whether it reported compliance with Task Force recommendations (compliant, non-compliant or not reported). This classification will serve as a stratification variable during synthesis, allowing separate consideration of findings from methodologically robust versus poorly reported studies. This approach balances the exploratory intent of scoping reviews with the need to contextualise the reliability of the evidence base.

Data analysis and presentation

Given the anticipated heterogeneity in study designs, measurement protocols and outcome definitions, quantitative meta-analysis is not planned. Instead, findings will be synthesised narratively and presented through four complementary approaches.

1. Temporal evidence mapping: This will categorise included studies by HRV measurement time point along the perioperative–postpartum continuum (preoperative >24 hour, preoperative <24 hour, intraoperative, immediate postoperative recovery, days 1–2, up to 6 weeks). A bubble chart or heat map will display the number of studies reporting each HRV parameter at each time point, visually identifying temporal windows with dense or sparse coverage.

2. Evidence gap map: An evidence gap map will be constructed following the approach described by Miake-Lye and colleagues.¹⁸ Studies will be cross-tabulated along two axes: HRV parameter tier (primary, secondary, tertiary) versus research orientation (haemodynamic prediction, complication prediction, descriptive HRV profiling, recovery assessment). Each cell will contain the number of available studies and their aggregate sample size, thereby revealing which intersections of parameter and application remain under-investigated.

3. Methodological quality stratification: This analysis will compare findings from studies classified as Task Force–compliant against those classified as non-compliant or unreported, to assess whether methodological rigour influences the reported associations between HRV and outcomes.

4. Correlation summary: This will narratively describe any reported associations between HRV indices and functional recovery measures (eg, ObsQoR-11, pain scores, time to ambulation), without pooling effect sizes. Subgroup stratifications will include elective versus emergency caesarean, neuraxial versus general anaesthesia, and adequacy of confounding factor control.

Patient and public involvement

Patients and members of the public were not directly involved in the design of this scoping review protocol. However, the research question was informed by clinical observations of recovery variability among caesarean patients in our institution and by informal feedback from postpartum women regarding the absence of objective recovery monitoring beyond routine vital signs. We intend to involve patient representatives in the interpretation and dissemination phases of the completed review to ensure that the findings are contextualised from the maternal perspective.

Protocol amendments

Any substantive amendments to this protocol made after OSF registration will be documented with the date of amendment, a description of the change and a rationale for the modification. All amendments will be reported transparently in the final scoping review manuscript.

Timeline

OSF protocol registration is planned for February 2026. Database searching will be conducted in March 2026. Title and abstract screening, followed by full-text assessment, is anticipated to require approximately 8 weeks (March–May 2026). Data extraction and verification will be completed by June 2026. Narrative synthesis and manuscript drafting are expected to span July–August 2026, with target submission in September 2026.

Limitations

This scoping review protocol has several inherent limitations. First, by restricting our search to English-language publications, we may miss relevant data from regions with high caesarean rates where research might be published in other languages. Second, excluding grey literature (like conference abstracts and dissertations) increases the risk of publication bias, meaning studies with null or negative findings might be underrepresented. Additionally, the rapid technological evolution of HRV monitoring, transitioning from traditional multi-lead ECGs to modern consumer-grade wearables, introduces significant methodological heterogeneity, which could complicate comparisons between older and more recent studies. Finally, the anticipated variability in study designs and outcome measures will likely prevent us from conducting any quantitative meta-analysis.

Data availability statement

Data sharing not applicable as no datasets generated and/or analysed for this study.