---
title: "S100B Protein as a Biomarker for Fetal Hypoxia in Late Growth Restriction: Study Protocol"
id: "plos-one-15-evaluating-cord-blood-s100b-protein-concentration-as-a-potential-biomarker"
canonical_url: "https://medichelpline.com/clinical-feed/plos-one-15-evaluating-cord-blood-s100b-protein-concentration-as-a-potential-biomarker"
content_type: "clinical_feed_article"
specialty: "Pediatrics"
source_name: "PLOS ONE (Medicine)"
source_url: "https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0355156"
published_at: "2026-08-05T14:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# S100B Protein as a Biomarker for Fetal Hypoxia in Late Growth Restriction: Study Protocol
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/plos-one-15-evaluating-cord-blood-s100b-protein-concentration-as-a-potential-biomarker
- **Specialty:** [Pediatrics](https://medichelpline.com/clinical-feed/pediatrics.md)
- **Primary Source:** PLOS ONE (Medicine)
- **Source URL:** [Original Journal Publication](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0355156)
- **Published At:** 2026-08-05T14:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- The study aims to investigate if **S100B protein** levels in cord blood can serve as a biomarker for fetal hypoxia in late **fetal growth restriction (FGR)**. - It involves two groups: one with prenatally diagnosed late FGR and a control with normal fetal growth. - Following birth, cord blood will be analyzed for S100B concentrations, pH, base excess, and lactate levels. - Fetal blood flow parameters via ultrasound will also be evaluated. - The study will compare S100B levels between both groups and seek correlations with fetal doppler parameters and blood gas analysis. - Ethical approval was obtained, and the findings will be published in relevant peer-reviewed journals. The study is registered at ClinicalTrials.gov.
## Clinical Analysis & Structured Key Points
Evaluating cord blood S100B protein concentration as a potential biomarker associated with fetal hypoxia in late fetal growth restriction: A prospective cohort study protocol | PLOS One Browse Subject Areas ? Click through the PLOS taxonomy to find articles in your field. For more information about PLOS Subject Areas, click here . Article Authors Metrics Comments Media Coverage Reader Comments Figures Figures Abstract Introduction S100B protein is a biomarker associated with central nervous system (CNS) injury following hypoxic-ischemic events. Measurement of S100B levels in umbilical cord blood may provide a noninvasive means of identifying newborns exposed to perinatal hypoxia related to fetal growth restriction (FGR) immediately after birth. Early detection of infants at increased risk of hypoxia-related CNS injury could facilitate closer surveillance, prompt diagnostic evaluation, and timely implementation of appropriate interventions, potentially improving long-term neurodevelopmental outcomes. Methods and Analysis This study investigates two groups of full-term pregnancies: a study group with prenatally diagnosed late FGR, and a control group with normal fetal growth. Following delivery, cord blood samples from both groups will be analyzed for S100B protein concentrations, pH, base excess (BE), and lactate levels. Additionally, fetal blood flow parameters in the umbilical artery (UA), uterine arteries (UtA), ductus venosus (DV), and middle cerebral artery (MCA) will be assessed via ultrasound within 48 hours before delivery. This study aims to compare S100B protein concentrations in umbilical cord blood between the two groups and evaluate its correlations with fetal Doppler parameters, pH, BE, and lactate levels in cord blood gas analysis. Additionally, it will evaluate the potential utility of S100B protein concentration as a biomarker associated with perinatal hypoxic stress in FGR-affected neonates. Ethics and Dissemination The study received approval from the Bioethics Committee of the Institute of Mother and Child in Warsaw (Decision No. 13/2024, dated 21 March 2024). The findings will be submitted for publication in peer-reviewed journals specializing in neonatology, pediatrics, obstetrics, and perinatology. Additionally, abstracts will be submitted to relevant national and international conferences. Trial registration The study is registered at ClinicalTrials.gov (Identifier: NCT06893926 ). Citation: Drozdowska-Szymczak A, Łukawska SA, Mazanowska N, Broniarek-Samson B, Zdulski J, Mierzejewska E, et al. (2026) Evaluating cord blood S100B protein concentration as a potential biomarker associated with fetal hypoxia in late fetal growth restriction: A prospective cohort study protocol. PLoS One 21(8): e0355156. https://doi.org/10.1371/journal.pone.0355156 Editor: Edward Mullins, Imperial College London, UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND Received: November 9, 2025; Accepted: July 8, 2026; Published: August 5, 2026 Copyright: © 2026 Drozdowska-Szymczak et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: No datasets were generated or analysed during the current study. All relevant data from this study will be made available upon study completion. Funding: This study was supported by the Institute of Mother and Child in Warsaw, Poland, from the institute’s internal resources. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Introduction Fetal hypoxia-ischemia (HI) presents a major challenge in perinatology due to its potential for causing severe complications in the child. Hypoxemia can result in brain damage, which may lead to conditions such as cerebral palsy, epilepsy, delayed psychomotor development, intellectual disability, and cognitive impairment [ 1 – 3 ]. Currently, the diagnosis of neonatal HI relies on a combination of prenatal and postnatal data. Abnormal UA and MCA blood flow parameters detected prenatally may indicate a risk of fetal HI. Postnatally, the diagnosis is based on neurological examination, laboratory tests, neurophysiological assessments, and imaging studies (such as ultrasound and MRI), along with ultrasonographic evaluation of blood flow parameters in the MCA and anterior cerebral artery (ACA) [ 1 , 3 ]. Despite these methods, some infants with CNS damage may not show immediate symptoms or abnormalities in additional tests after birth, highlighting the need for improved early identification strategies. Cord blood biomarkers, such as the S100B, are therefore of significant interest [ 1 – 11 ]. S100B is a calcium-binding regulatory protein found in the cytoplasm of brain cells. In cases of CNS damage, such as hypoxia, S100B is released into the bloodstream, resulting in elevated levels in cerebrospinal fluid and umbilical cord blood [ 2 , 8 , 12 ]. This allows for the noninvasive assessment of the biomarker’s concentration immediately after birth. Due to its short half-life, S100B facilitates the recognition and monitoring of CNS damage progression, with its concentration correlating with the severity of hypoxia. Other factors that can elevate S100B levels in a newborn’s bloodstream and cord blood include chorioamnionitis, preterm birth, prolonged vaginal labor (lasting over 15 hours), and operative delivery [ 5 , 13 – 17 ]. Conversely, significantly lower S100B levels have been observed in infants born to mothers treated with selective serotonin reuptake inhibitors (SSRIs) [ 18 ]. Higher concentrations of S100B protein have been reported in cases of chronic hypoxia, particularly in newborns diagnosed with FGR or small for gestational age (SGA), where birth weight is below the 10th percentile. However, these findings are sometimes contradictory [ 1 – 3 , 6 ]. Among neonates with FGR, significantly higher S100B concentrations have been observed in the umbilical vessels of those with abnormal prenatal blood flow in the UA compared to those with normal flow parameters [ 2 , 6 ]. In the FGR group, elevated S100B protein levels have also been linked to an increased risk of necrotizing enterocolitis (NEC), the need for intubation, mortality, and, according to some studies, the occurrence of intraventricular hemorrhage (IVH) [ 5 , 6 ]. In growth-restricted neonates, there is a noted correlation between neurological developmental disorders and blood flow parameters in the fetal MCA. However, the impact of the severity of blood flow impairment in the fetal brain on S100B concentration has not yet been studied [ 19 ]. Assessing cord blood S100B protein concentration may enable the early identification of newborns at high risk for abnormal development, even when standard biochemical or clinical parameters and neurological assessments reveal no abnormalities. Furthermore, identifying a child at risk on the first day of life through noninvasive methods could enable early planning for systematic pediatric and physiotherapy care. This proactive approach would allow for the timely initiation of rehabilitation, potentially improving neurodevelopmental outcomes in infants affected by intrauterine growth disorders. Methods and analysis The protocol was prepared with consideration of STROBE recommendations applicable to observational cohort studies [ 20 , 21 ] and registered at ClinicalTrials.gov (NCT06893926) on March 25, 2025 ( https://clinicaltrials.gov/study/NCT06893926 ). Objectives The study aims to: Determine whether the cord blood S100B protein concentration is significantly higher in neonates with prenatally diagnosed FGR compared to controls. Evaluate the correlation between S100B protein concentration and fetal blood flow parameters in the UA, UtA, DV, and MCA, as assessed by ultrasound performed within 48 hours before delivery. Evaluate the discriminatory performance of S100B concentration in relation to perinatal markers associated with fetal hypoxia (pH, BE, and lactate levels in umbilical artery blood). Trial design This single-center, prospective cohort study aims to assess the effectiveness of S100B protein concentration as a potential biomarker associated with perinatal hypoxic stress in neonates with FGR, compared to a control group without growth disorders. Study setting The study is being conducted at the Institute of Mother and Child in Warsaw, specifically within the Department of Obstetrics and Gynecology and the Department of Neonatology and Neonatal Intensive Care, both of which function as tertiary referral units. The center manages approximately 50 full-term newborns diagnosed with FGR annually. Recruitment commenced in June 2024 and was initially projected to continue for approximately 18 months, through December 2025, with the actual duration dependent on the number of FGR patients enrolled during that period. Complete data collection is expected to be finalized within three months of the end of recruitment (March 2026), with initial results anticipated in June 2026. At the time of protocol publication, the authors anticipated potential minor delays in patient recruitment due to a lower-than-expected incidence of pregnancies complicated by FGR at the study center, as well as a higher-than-anticipated number of exclusions. As of September 2025, approximately two-thirds of the targeted patient population have been enrolled in both the study and control groups. Definitions Fenton’s growth charts are used to assess birth weight percentiles [ 22 ]. The criteria for diagnosing FGR follow the 2020 recommendations of the Polish Society of Gynecologists and Obstetricians for late-onset growth restriction, which occurs after the 32nd week of pregnancy [ 23 ]. These guidelines are based on the Delphi Criteria for diagnosing early and late FGR [ 24 ]. Late FGR is diagnosed if any of the following criteria are detected during routine fetal ultrasound: Abdominal circumference (AC) below the 3rd percentile for the given gestational age. Estimated fetal weight (EFW) below the 3rd percentile for the given gestational age. OR EFW or AC below the 10th percentile, along with at least one of the following: Growth retardation by the 50th percentile on the growth curve. Cerebroplacental index (CPR), defined as the ratio of the pulsatility indices (PI) in the MCA and UA, below the 5th percentile for the given gestational age. UA PI above the 95th percentile for the given gestational age. Eligibility criteria Study group – Inclusion criteria. Women with a full-term, singleton pregnancy (≥37 + 0/7 weeks of gestation). Pregnancy complicated by late-onset FGR. Study group – Exclusion criteria. Antenatal (at recruitment): Maternal conditions that may affect the blood flow in placental vessels, including smoking, use of illicit stimulant substances, or pregestational diabetes. Maternal depression requiring pharmacological treatment (e.g., SSRIs). Intrapartum: Factors indicating a possible intrauterine infection, such as amniotic fluid leakage for more than 15 hours, spontaneous preterm labor, diagnosed intrauterine infection, or maternal symptoms of infection. Prolonged labor lasting more than 15 hours. Given the data on increased S100B level in labor exceeding 15 hours, this duration of amniotic fluid leakage was set as the cutoff point in the exclusion criteria [ 5 , 17 ]. Control Group – Inclusion criteria. Women with a full-term, singleton pregnancy (≥37 + 0/7 weeks of gestation). Pregnancy not complicated by FGR. Control Group – Exclusion criteria. Antenatal (at recruitment): Maternal conditions that may affect placental blood flow, such as smoking, use of illicit stimulant substances, pregestational diabetes, or chronic hypertension. Maternal depression requiring pharmacological treatment (e.g., SSRIs). Risk factors for intrauterine HI, including abnormal fetal blood flow parameters on ultrasound, abnormal CTG recordings, or the need for intrauterine transfusion (IUT). Intrapartum: Indicators of possible intrauterine infection, such as amniotic fluid leakage for more than 15 hours, spontaneous preterm delivery, diagnosed intrauterine infection, or maternal symptoms of infection. Risk factors for perinatal HI. Prolonged labor lasting more than 15 hours (counted from the onset of regular uterine contractions). Birth weight below the 10th percentile or above the 90th percentile. Apgar score less than 8 at the 1st, 3rd, 5th, or 10th minute of life. Abnormal umbilical cord blood gas analysis results, defined as pH < 7.15 or BE < −9.3 mmol/l. Postnatal: Neonatal anemia requiring a top-up transfusion within the first 24 hours of life. The exclusion criteria for the study and control groups differ based on the principle that the control group should consist of healthy neonates without risk factors for HI. In contrast, the study group includes infants diagnosed with FGR, who inherently have a higher risk of complications. These complications, such as a low Apgar score, abnormal umbilical cord blood gas analysis parameters, or an abnormal CTG recording, are precisely the factors that serve as exclusion criteria for the control group. This approach ensures that the control group provides a valid baseline for comparison against the at-risk study group. In patients with a singleton, full-term pregnancy who present to the labor and delivery unit and meet the inclusion criteria, without meeting the antenatal exclusion criteria (except for those related to FGR), informed written consent for testing is obtained prior to delivery. The mother is also informed that if any exclusion criteria are identified during or after delivery, the child will be disqualified from further participation in the study. To account for the potential influence of the mode of delivery (vaginal delivery [VD] or cesarean section [CS]) on S100B protein concentration, the study aims to balance the proportion of neonates delivered by each method between the study and control groups. As recruitment progresses, the number of pregnancies delivered by VD and CS in the study group will be monitored. Recruitment in the control group will be adjusted based on the mode of delivery to ensure that the percentage of CS is similar in both groups. This approach aims to minimize any confounding effects of the delivery method on the study outcomes. Study procedures and data collection Data will be collected through cord blood samples, ultrasound measurements, and clinical assessments. For all patients who consent to participate in the study, an ultrasound examination will be performed within 48 hours before delivery. This ultrasound assessment includes: a. Measurement of the fetus’s anthropometric dimensions and estimation of fetal weight. b. Evaluation of blood flow using the pulsatility index (PI) in the UA, UtA, DV, and MCA. After birth, in both the study and control groups: A 1.5 ml blood sample will be collected from the clamped part of the umbilical cord: a. Immediate analysis: 0.5 ml of the cord blood will be sent immediately to the laboratory to determine pH, BE, and lactate levels in the umbilical cord blood analysis. b. S100B protein analysis: The remaining 1 ml of cord blood will be placed in a labeled tube (including the mother’s name, child’s gender, date of birth, and date of collection) and sent to the laboratory for centrifugation. Serum samples will be frozen at −20°C and stored. Once approximately 80 samples are collected, the serum will be thawed and analyzed for S100B protein concentration. Any remaining material after laboratory processing will be properly disposed of. Data will be collected on gestational age, duration, and mode of delivery, along with any complications encountered during delivery. Additionally, details regarding the newborn’s condition after birth will be recorded, including gender, Apgar score, and anthropometric measurements. Observations made during hospitalization will also be documented, with particular attention to any concerning symptoms related to the CNS, such as muscle tone abnormalities or seizures. A transfontanelle ultrasound examination will be performed to assess for any abnormalities in the newborn. Study participation does not alter standard hospitalization procedures or duration. Furthermore, collecting a blood sample for the planned tests will not interfere with cord blood collection if the mother intends to bank it. Criteria for discontinuing participation If a full ultrasound flow assessment becomes unfeasible due to technical issues, advanced labor, or urgent delivery indications, it will be halted. However, any partial data collected will still be analyzed. If an umbilical cord blood sample cannot be collected after birth, the patient will be excluded from the study. Nevertheless, data from excluded patients will be retained to support further analysis and ensure a comprehensive statistical evaluation. In cases where consent is withdrawn, any data collected up to that point will be retained and used in the study. Compliance Before the study commenced, a meeting was held to familiarize the researchers and staff with the study protocol. The protocol was presented in detail, including the rationale behind the study. Additionally, schematic instructions were provided, covering patient qualification, the required tests for qualification, and the intervention procedures. The medical records of participating patients are clearly labeled to ensure adherence to the study protocol. Each patient’s medical record includes a schematic outlining the inclusion and exclusion criteria. Explanation for the choice of comparators Biomarkers associated with the risk of hypoxia-related CNS injury should meet several key criteria: They should be detectable in easily accessible fluids such as blood, amniotic fluid, or urine, allowing for straightforward sample collection. They should identify patients at risk before symptoms emerge or clinical examinations, or other tests (e.g., ultrasound, MRI, or EEG) reveal any abnormalities. They should provide a quantitative measure of the severity of perinatal hypoxic stress. The tests should be simple, quick, cost-effective, and characterized by repeatability, sensitivity, and specificity [ 25 ]. To date, few markers have been thoroughly evaluated for each of these criteria. However, the S100B protein shows promise as a potential marker. It can be detected in blood, saliva, urine, and amniotic fluid, potentially allowing for the early identification of neonates at risk of adverse neurodevelopmental outcomes in a relatively quick and inexpensive manner. Nonetheless, additional prospective studies are needed. Outcome measures The study’s primary endpoint will be the concentration of S100B protein measured from a cord blood sample taken after birth in both the study and control groups. Additional endpoints will include: The potential correlation between S100B concentration and pH, BE, and lactate levels, as determined in the cord blood gas analysis in both the study and control groups. The possible relationship between cord blood S100B protein concentration and blood flow parameters (PI) in the UA, UtA, DV, and MCA, as assessed by fetal ultrasound performed within 48 hours before delivery. Participant timeline For the primary endpoint data acquisition, the study period includes the fetal ultrasound examination conducted 48 hours before delivery and the delivery process itself. This encompasses umbilical cord clamping, collecting cord blood from the severed portion of the umbilical cord, and recording anthropometric measurements. Additional data that may lead to patient exclusion (e.g., diagnosis of intrauterine infection or neonatal anemia requiring a top-up transfusion in the control group) or
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