Recognition of chronic hypoxia and pre-existing foetal injury on the cardiotocograph (CTG): Urgent need to think beyond the guidelines

Relative uteroplacental insufficiency of labor

Relative uteroplacental insufficiency of labor (RUPI-L) is a clinical condition that refers to alterations in the fetal oxygen "demand-supply" equation caused by the onset of regular uterine activity. The term RUPI-L indicates a condition of "relative" uteroplacental insufficiency which is relative to a specific stressful circumstance, such as the onset of regular uterine activity. RUPI-L may be more prevalent in fetuses in which the ratio between the fetal oxygen supply and demand is already slightly reduced, such as in cases of subclinical placental insufficiency, post-term pregnancies, gestational diabetes, and other similar conditions. Prior to the onset of regular uterine activity, fetuses with a RUPI-L may present with normal features on the cardiotocography. However, with the onset of uterine contractions, these fetuses start to manifest abnormal fetal heart rate patterns which reflect the attempt to maintain adequate perfusion to essential central organs during episodes of transient reduction in oxygenation. If labor is allowed to continue without an appropriate intervention, progressively more frequent, and stronger uterine contractions may result in a rapid deterioration of the fetal oxygenation leading to hypoxia and acidosis. In this Commentary, we introduce the term relative uteroplacental insufficiency of labor and highlight the pathophysiology, as well as the common features observed in the fetal heart rate tracing and clinical implications.

Machine learning on cardiotocography data to classify fetal outcomes: A scoping review

INTRODUCTION

Uterine contractions during labour constrict maternal blood flow and oxygen delivery to the developing baby, causing transient hypoxia. While most babies are physiologically adapted to withstand such intrapartum hypoxia, those exposed to severe hypoxia or with poor physiological reserves may experience neurological injury or death during labour. Cardiotocography (CTG) monitoring was developed to identify babies at risk of hypoxia by detecting changes in fetal heart rate (FHR) patterns. CTG monitoring is in widespread use in intrapartum care for the detection of fetal hypoxia, but the clinical utility is limited by a relatively poor positive predictive value (PPV) of an abnormal CTG and significant inter and intra observer variability in CTG interpretation. Clinical risk and human factors may impact the quality of CTG interpretation. Misclassification of CTG traces may lead to both under-treatment (with the risk of fetal injury or death) or over-treatment (which may include unnecessary operative interventions that put both mother and baby at risk of complications). Machine learning (ML) has been applied to this problem since early 2000 and has shown potential to predict fetal hypoxia more accurately than visual interpretation of CTG alone. To consider how these tools might be translated for clinical practice, we conducted a review of ML techniques already applied to CTG classification and identified research gaps requiring investigation in order to progress towards clinical implementation.

MATERIALS AND METHOD

We used identified keywords to search databases for relevant publications on PubMed, EMBASE and IEEE Xplore. We used Preferred Reporting Items for Systematic Review and Meta-Analysis for Scoping Reviews (PRISMA-ScR). Title, abstract and full text were screened according to the inclusion criteria.

RESULTS

We included 36 studies that used signal processing and ML techniques to classify CTG. Most studies used an open-access CTG database and predominantly used fetal metabolic acidosis as the benchmark for hypoxia with varying pH levels. Various methods were used to process and extract CTG signals and several ML algorithms were used to classify CTG. We identified significant concerns over the practicality of using varying pH levels as the CTG classification benchmark. Furthermore, studies needed to be more generalised as most used the same database with a low number of subjects for an ML study.

CONCLUSION

ML studies demonstrate potential in predicting fetal hypoxia from CTG. However, more diverse datasets, standardisation of hypoxia benchmarks and enhancement of algorithms and features are needed for future clinical implementation.

The effects of inflammation and acidosis on placental blood vessels reactivity

INTRODUCTION

Inflammation and acidosis are two stress stimuli that correspond to pathophysiological processes occurring in placental-mediated vascular disorders. We aimed to investigate the effects of these stimuli on placental chorionic blood vessels reactivity using the ex-vivo placental perfusion model.

METHODS

Term placentas were obtained immediately after cesarean deliveries, and selected cotyledons were cannulated and dually perfused ex-vivo. Placentas were perfused with three different protocols: culture medium (M199-controls, n = 5), culture medium with lipopolysaccharide (inflammatory stimuli) (LPS,1 μg/ml, n = 7), and acidotic culture medium (M - 199, pH: 6.9-7, n = 6). Each perfusion experiment was maintained for 180 min. Fetal perfusion pressure was continuously measured. Measurements in response to angiotensin II (AT II) at the end of the perfusion were compared between the treatment groups, including amplitude of the contraction response, relaxation factor, time to maximal constriction and the area under the pressure curve (AUC).

RESULTS

In response to ATII there was a significant difference in the amplitude of the contraction and the AUC between the treatment groups, (p = 0.049, p = 0.015, respectively). As compared with control perfused cotyledon, the inflammatory stimuli significantly increased the vasoconstriction response to ATII in fetal placental blood vessels, as expressed by increased AUC - median (IQR): 555 (235-1184) vs. 133 (118-207), respectively, p = 0.017. The time to maximal constriction and the relaxation factor did not differ between the groups.

DISCUSSION

Inflammatory stimuli but not acidosis impact fetal-placental vasculature in response to ATII, suggesting that inflammation can compromise vascular function.

Pathophysiological interpretation of fetal heart rate tracings in clinical practice

The onset of regular, strong, and progressive uterine contractions may result in both mechanical (compression of the fetal head and/or umbilical cord) and hypoxic (repetitive and sustained compression of the umbilical cord or reduction in uteroplacental oxygenation) stresses to a human fetus. Most fetuses are able to mount effective compensatory responses to avoid hypoxic-ischemic encephalopathy and perinatal death secondary to the onset of anaerobic metabolism within the myocardium, culminating in myocardial lactic acidosis. In addition, the presence of fetal hemoglobin, which has a higher affinity for oxygen even at low partial pressures of oxygen than the adult hemoglobin, especially increased amounts of fetal hemoglobin (ie, 180-220 g/L in fetuses vs 110-140 g/L in adults), helps the fetus to withstand hypoxic stresses during labor. Different national and international guidelines are currently being used for intrapartum fetal heart rate interpretation. These traditional classification systems for fetal heart rate interpretation during labor are based on grouping certain features of fetal heart rate (ie, baseline fetal heart rate, baseline variability, accelerations, and decelerations) into different categories (eg, category I, II, and III tracings, "normal, suspicious, and pathologic" or "normal, intermediary, and abnormal"). These guidelines differ from each other because of the features included within different categories and because of their arbitrary time limits stipulated for each feature to warrant an obstetrical intervention. This approach fails to individualize care because the "ranges of normality" for stipulated parameters apply to the population of human fetuses and not to the individual fetus in question. Moreover, different fetuses have different reserves and compensatory responses and different intrauterine environments (presence of meconium staining of amniotic fluid, intrauterine inflammation, and the nature of uterine activity). Pathophysiological interpretation of fetal heart rate tracing is based on the application of the knowledge of fetal responses to intrapartum mechanical and/or hypoxic stress in clinical practice. Both experimental animal studies and observational human studies suggest that, just like adults undertaking a treadmill exercise, human fetuses show predictable compensatory responses to a progressively evolving intrapartum hypoxic stress. These responses include the onset of decelerations to reduce myocardial workload and preserve aerobic metabolism, loss of accelerations to abolish nonessential somatic body movements, and catecholamine-mediated increases in the baseline fetal heart rate and effective redistribution and centralization to protect the fetal central organs (ie, the heart, brain, and adrenal glands), which are essential for intrauterine survival. Moreover, it is essential to incorporate the clinical context (progress of labor, fetal size and reserves, presence of meconium staining of amniotic fluid and intrauterine inflammation, and fetal anemia) and understand the features suggestive of fetal compromise in nonhypoxic pathways (eg, chorioamnionitis and fetomaternal hemorrhage). It is important to appreciate that the timely recognition of the speed of onset of intrapartum hypoxia (ie, acute, subacute, and gradually evolving) and preexisting uteroplacental insufficiency (ie, chronic hypoxia) on fetal heart rate tracing is crucial to improve perinatal outcomes.

Abnormal heart rate pattern in fetal anaemia secondary to transient abnormal myelopoeisis in a fetus without trisomy 21: A case report

Decreased fetal movements (DFM) are a non-specific and common symptom in the third trimester of pregnancy that hold an association with fetal compromise. A 28-year-old woman at 31 weeks and 3 days of gestation presented with DFM and was found to have a pathological fetal heart rate trace. Following emergency Caesarean section the fetus was diagnosed with transient abnormal myelopoeisis (TAM). Timely treatment was initiated and the neonatal outcome was good. Transient myeloproliferative disorders are almost uniquely found in infants with trisomy 21 (T21). This is the first case report of TAM in the absence of T21 wherein the diagnostic process was commenced antenatally due to non-reassuring fetal status and highlights the importance of antenatal heart rate abnormalities.

Abnormal fetal heart rate patterns caused by pathophysiologic processes other than fetal acidemia

Fetal acidemia is a common final pathway to fetal death, and in many cases, to fetal central nervous system injury. However, certain fetal pathophysiological processes are associated with significant category II or category III fetal heart rate changes before the development of or in the absence of fetal acidemia. The most frequent of these processes include fetal infection and/or inflammation, anemia, fetal congenital heart disease, and fetal central nervous system injury. In the presence of significant category II or category III fetal heart rate patterns, clinicians should consider the possibility of the aforementioned fetal processes depending on the clinical circumstances. The common characteristic of these pathophysiological processes is that their associated fetal heart rate patterns are linked to increased adverse neonatal outcomes despite the absence of acidemia at birth. Therefore, in these cases, the fetal heart rate patterns may provide more insight about the fetal condition and pathophysiology than the acid-base status at birth. In addition, as successful timing of intrapartum interventions on the basis of evolution of fetal heart rate patterns aims to prevent fetal acidemia, it may not be logical to continue to use the fetal acid-base status at birth as the gold standard outcome to determine the predictive ability of category II or III fetal heart rate patterns. A more reasonable approach may be to use the umbilical cord blood acid-base status at birth as the gold standard for determining the appropriateness of the timing of our interventions.

Pustular psoriasis of pregnancy: A rare cause of placental insufficiency

Generalised pustular psoriasis of pregnancy (GPPP) is a rare dermatosis that presents in the third trimester. It merits careful clinical assessment given the difficulty in diagnosis, impact on maternal health and association with placental insufficiency. We present a case of generalised pustulosis in a pregnant woman at 30 weeks gestation and describe the clinico-pathological challenges in obtaining a diagnosis of GPPP. Furthermore, we provide evidence from cardiotocography and ultrasound of evolving fetal compromise and describe how intensive management can facilitate a positive maternal–fetal outcome.

Physiological CTG categorization in types of hypoxia compared with MRI and neurodevelopmental outcome in infants with HIE

BACKGROUND

Commonly used methods of CTG classification do not reliably predict neonatal hypoxic-ischemic encephalopathy (HIE).

OBJECTIVE

To examine whether a relationship exists between the types of hypoxia as identified on the cardiotocograph using novel physiology-based CTG classification and patterns of injury on neonatal cerebral MRI and later neurodevelopmental outcomes.

STUDY DESIGN

A retrospective study of term-born infants admitted to four neonatal units with HIE as part of a brain injury biomarkers study between January 2014 and December 2015. Intrapartum CTG traces were analyzed by two obstetricians trained in physiological CTG classification, blind to neonatal outcomes. Neonatal cerebral MR images were assessed independently by a neuroradiologist and an expert neonatologist. CTG traces were classified into types of hypoxia and allocated to groups; (1) chronic hypoxia or antepartum injury; (2) gradually evolving or subacute hypoxia; and (3) acute hypoxia.

RESULTS

Of 106 infants recruited to the study, records were available for 58 cases. Of these, CTGs were available for 37. All 37 had abnormal CTGs. Twenty-four infants, all of whom had received therapeutic hypothermia had cerebral MRI. Fourteen of the 24 (58%) infants had abnormal MRI. In group 1 (chronic hypoxia/antenatal injury), total brain injury was most predominant (4/6 infants). Group 2 (gradually evolving/subacute hypoxia) was associated with peripheral brain injury (5/5 infants). Group 3 (acute hypoxia) was associated with basal-ganglia thalamic injury pattern (3/3 infants). Later neurodevelopmental outcomes were available for 35 cases. Infants suspected to have a pre-labor injury on CTG (group 1) had a higher proportion of adverse neurodevelopmental outcomes (4/10, 40%) compared to groups 2 and 3 (4/25, 16%).

CONCLUSION

Using this novel physiology-based CTG classification, we demonstrate an association between types of hypoxia observed on the CTG and MRI patterns of hypoxic brain injury. Infants with CTG trace suggestive of chronic hypoxia or other antenatal injuries were overrepresented in this cohort and were also more likely to have a poor neurodevelopmental outcome.

Severe Neonatal Anemia Due to Spontaneous Massive Fetomaternal Hemorrhage at Term: An Illustrative Case with Suspected Antenatal Diagnosis and Brief Review of Current Knowledge

Fetomaternal hemorrhage is defined as transfer of fetal blood into placental circulation and therefore into maternal circulation during pregnancy, and represents an important contributor to intrauterine fetal demise and neonatal death. The condition is rarely diagnosed prenatally because clinical findings are often nonspecific, and it is unpredictable. In this paper we present an illustrative case of massive spontaneous fetomaternal hemorrhage where the diagnosis was highly suspected antenatally based on maternal reported reduced fetal movements, abnormal suggestive cardiotocographic trace, and increased peak systolic velocity in the fetal middle cerebral artery. We discuss obstetrical and neonatal management and review the current knowledge in the literature. Maintaining a high index of suspicion for this condition allows the obstetrician to plan for adequate diagnostic tests, arrange intrauterine treatment or delivery, and prepare the neonatal team.

Absence of Wharton's Jelly at the Abdominal Site of the Umbilical Cord Insertion. Rare Case Report and Review of the Literature

Wharton’s jelly is a specialized connective tissue surrounding and protecting umbilical cord vessels. In its absence, the vessels are exposed to the risk of compression or rupture. Because the condition is very rare and there are no available antepartum investigation methods for diagnosis, these cases are usually discovered after delivery, frequently after in utero fetal demise. We report the fortunate case of a 29-year-old nulliparous woman, with an uncomplicated pregnancy, admitted at 39 weeks in labor where a persistently abnormal cardiotocographic trace led to delivery by cesarean section of a healthy 3500 g newborn. After delivery, a Wharton’s jelly anomaly was identified at the abdominal umbilical insertion (umbilical cord vessels, approximately 1 cm in length, were completely uncovered by Wharton’s jelly), which required surgical thread elective ligation. In the presence of a persistently abnormal CTG trace, in a pregnancy with no clinical settings suggestive of either chronic or acute fetal hypoxemia, the absence of Wharton’s jelly should be taken into consideration in the differential diagnosis.

Absence of fetal heart rate cycling on the intrapartum cardiotocograph (CTG) is associated with intrapartum pyrexia and lower Apgar scores

BACKGROUND

Cycling consists of alternating periods of reduced and normal fetal heart variability, reflecting changes in fetal behavioral states. Occurrence of active and quiet sleep cycles is considered to be a hallmark of fetal autonomic nervous system integrity, demonstrating healthy interaction between the parasympathetic and sympathetic nervous systems. Cycling is an overlooked feature in most international cardiotocography (CTG) guidelines. The authors tested the hypothesis that fetuses showing no cycling in the intrapartum period have poorer outcomes.

AIM

To investigate whether the absence of cycling at the commencement of intrapartum fetal monitoring is associated with poorer neonatal outcomes (umbilical arterial cord pH, Apgar scores and neonatal unit admission).

METHODS

Analysis of a database of sequentially acquired intrapartum CTG traces from a single center. Only cases of singleton pregnancies over 36 weeks gestation in cephalic presentation with recorded umbilical artery cord pH were considered. Neonatal outcomes were assessed based on umbilical cord artery pH, Apgar ≤7 at 5 min and unexpected admission to the neonatal unit. Intrapartum pyrexia, presence of meconium-stained amniotic fluid and mode of delivery were also recorded.

RESULTS

A total of 684 cases were analyzed. Absence of cycling from the beginning of the intrapartum CTG recording was noted in 5% of cases. Cases with no cycling were more likely to have maternal pyrexia (≥37.8 °C) (p = .006) and Apgars ≤7 at 5 min (p = .04). There was an association between increasing baseline fetal heart rate and the proportion of cases with no cycling. There was no significant difference between the two groups with regard to the mode of delivery or umbilical cord arterial pH <7.05 (p = .53).

CONCLUSION

Absence of cycling is associated with intrapartum maternal pyrexia and fetuses with the absence of cycling are more likely to have poorer perinatal outcomes measured by Apgar ≤ 7 at 5 min, despite no association with fetal acidosis. Results from this research were presented at the XXVI European Congress of Perinatal Medicine in September 2018.

Monitoring fetal well-being in labor in late fetal growth restriction

Late-onset fetal growth restriction (FGR) accounts for approximately 70-80% of all cases of FGR secondary to uteroplacental insufficiency. It is associated with an increased incidence of adverse antepartum and perinatal events, which in most instances result from hypoxic insults either present at the onset of labor or supervening during labor as a result of uterine contractions. Labor represents a stressful event for the fetoplacental unit being uterine contractions associated with an up-to 60% reduction of the uteroplacental perfusion. Intrapartum fetal heart rate monitoring by means of cardiotocography (CTG) currently represents the mainstay for the identification of fetal hypoxia during labor and is recommended for the fetal surveillance during labor in the case of FGR or other conditions associated with an increased risk of intrapartum hypoxia. In this review we discuss the potential implications of an impaired placental function on the intrapartum adaptation to the hypoxic stress and the role of the CTG and alternative techniques for the intrapartum monitoring of the fetal wellbeing in the context of FGR secondary to uteroplacental insufficiency.

Fetal heart rate monitoring in labor: from pattern recognition to fetal physiology

The journey of human labor involves hypoxic and mechanical stresses as a result of progressively increasing frequency, duration and strength of uterine contractions and resultant compression of the umbilical cord. In addition, occlusion of the spiral arteries during myometrial contractions also leads to repetitive interruptions in the utero-placental circulation, predisposing a fetus to progressively worsening hypoxic stress as labor progresses. The vast majority of fetuses are equipped with compensatory mechanisms to withstand these hypoxic and mechanical stresses. They emerge unharmed at birth. However, some fetuses may sustain an antenatal injury or experience a chronic utero-placental insufficiency prior to the onset of labor. These may impair the fetus to compensate for the ongoing hypoxic stress secondary to ongoing uterine contractions. Non-hypoxic pathways of neurological damage such as chorioamnionitis, fetal anemia or an acute fetal hypovolemia may potentiate fetal neurological injury, especially in the presence of a super-imposed, additional hypoxic stress. The use of utero-tonic agents to induce or augment labor may increase the risk of hypoxic-ischemic injury. Clinicians need to move away from "pattern recognition" guidelines ("normal," "suspicious," "pathological"), and apply the knowledge of fetal physiology to differentiate fetal compensation from decompensation. Individualization of care is essential to optimize outcomes.

Intrapartum fetal heart rate between 150 and 160 bpm at or after 40 weeks and labor outcome

INTRODUCTION

A baseline fetal heart rate between 110 and 160 bpm is considered normal. However, among normal fetuses the average baseline heart rate has been shown to diminish progressively and the 90th centile of the fetal heart rate at 40 weeks of gestation has been consistently found at around 150 bpm. The aim of our study was to assess the labor and neonatal outcome of fetuses at 40 gestational weeks or beyond, whose intrapartum baseline fetal heart rate was between 150 and 160 bpm.

MATERIAL AND METHODS

Retrospective cohort study including singleton pregnancies with spontaneous onset of labor, gestational age between 40⁺⁰ and 42⁺⁰ weeks, category I CTG trace according to the FIGO guidelines 2015 with baseline fetal heart rate between 110 and 160 bpm during the first 60 minutes of active labor. Exclusion criteria were maternal hyperpyrexia at admission, fetal arrhythmias, maternal tachycardia (>110 bpm) and uterine tachysystole (>5 contractions/10 minutes). The following outcomes were compared between fetuses with a baseline ranging between 110 and 149 bpm and those with a baseline ranging between 150 and 160 bpm: incidence of meconium-stained amniotic fluid, intrapartum hyperpyrexia, mode of delivery, Apgar at 5 minutes <7, arterial pH <7.1 and Neonatal Intensive Care Unit admission, incidence of a composite adverse neonatal outcome.

RESULTS

In all, 1004 CTG traces were included in the analysis, 860 in Group 110-149 bpm and 144 in Group 150-160 bpm. Group 150-160 bpm had a significantly higher incidence of meconium-stained amniotic fluid (odds ratio [OR] 2.6; 95% CI 1.8-3.8), maternal intrapartum hyperpyrexia (OR 4.7; 95% CI 1.1-14.6), urgent/emergent cesarean section for suspected fetal distress (OR 13.4; 95% CI 3.3-54.3), Apgar <7 at 5th min (OR 9.13; 95% CI 1.5-55.1) and neonatal acidemia (OR 3.5; 95% CI 1.5-55.1). Logistic regression including adjustiing for potential confounders showed that fetal heart rate between 150 and 160 bpm is an independent predictor of meconium-stained amniotic fluid (adjusted odds ratio [aOR] 2.2; 95% CI 1.5-3.3), cesarean section during labor for fetal distress (aOR 10.7; 95% CI 2.9-44.6), neonatal acidemia (aOR 2.6; 95% CI 1.1-6.7) and adverse composite neonatal outcome (aOR 2.6; 95% CI 1.2-5.6).

CONCLUSIONS

In fetuses at 40 weeks or beyond, an intrapartum fetal heart rate baseline ranging between 150 and 160 bpm seems associated with a higher incidence of labor complications.

Visual assessment of heart rate variability patterns associated with neonatal infection in preterm infants

Early identification of neonatal sepsis may help reduce morbidity. From Heart Rate Variability (HRV) visually assessed in preterm infants, eight of nine recordings in babies with positive blood cultures had low HRV and six infants without positive cultures had normal HRV. Straightforward HRV display could help identify infection in infants.