Peripheral chemoreflex control of fetal heart rate decelerations overwhelms the baroreflex during brief umbilical cord occlusions in fetal sheep

Interdisciplinary fetal-neonatal neurology training improves brain health across the lifespan

Integrated fetal, neonatal, and pediatric training constitute an interdisciplinary fetal-neonatal neurology (FNN) program. A dynamic neural exposome concept strengthens curriculum content. Trainees participate in mentoring committee selection for guidance during a proposed two-year program. Prenatal to postnatal clinical learning re-enforces early toxic stressor interplay that influences gene-environment interactions. Maternal-placental-fetal triad, neonatal, or childhood diseases require diagnostic and therapeutic decisions during the first 1,000 days when 80 % of neural connections contribute to life-course phenotypic expression. Pediatric follow-up through 3 years adjusts to gestational ages of preterm survivors. Cumulative reproductive, pregnancy, pediatric and adult exposome effects require educational experiences that emphasize a principle-to-practice approach to a brain capital strategy across the lifespan. More rigorous training during fetal, neonatal, and pediatric rotations will be offered to full time trainees. Adult neurology residents, medical students, and trainees from diverse disciplines will learn essential topics during time-limited rotations. Curriculum content will require periodic re-assessments using educational science standards that maintain competence while promoting creative and collaborative problem-solving. Continued career-long learning by FNN graduates will strengthen shared healthcare decisions by all stakeholders. Recognition of adaptive or maladaptive neuroplasticity mechanisms requires analytic skills that identify phenotypes associated with disease pathways. Developmental origins and life-course concepts emphasize brain health across the developmental-aging continuum, applicable to interdisciplinary research collaborations. Social determinants of health recognize diversity, equity, and inclusion priorities with each neurological intervention, particularly for those challenged with disparities. Diagnostic and therapeutic strategies must address resource challenges particularly throughout the Global South to effectively lower the worldwide burden of neurologic disease. Sustainable development goals proposed by the World Health Organization offer universally applicable guidelines in response to ongoing global and regional polycrises. Gender, race, ethnicity, and socio-economic equality promote effective preventive, rescue and reparative neuroprotective interventions. Global synergistic efforts can be enhanced by establishing leadership within academic teaching hubs in FNN training to assist with structure and guidance for smaller healthcare facilities in each community that will improve practice, education and research objectives. Reduced mortality with an improved quality of life must prioritize maternal-pediatric health and well-being to sustain brain health across each lifespan with transgenerational benefits.

Changes in fetal baroreceptor sensitivity during intrauterine inflammation in preterm fetal sheep

OBJECTIVE

Baroreflex is a regulatory mechanism that slows the fetal heart rate. This study aimed to investigate the effects of lipopolysaccharide (LPS)-induced endotoxemia on fetal baroreceptor sensitivity in preterm fetal sheep.

METHODS

The changes in fetal baroreceptor sensitivity were measured in seven chronically instrumented preterm fetal sheep. Fetal baroreceptor sensitivity was measured in three phases: (A) control phase, defined as the 24 h before the first injection of LPS; (B) acute phase, defined as the 24 h between the first and second injections of LPS; and (C) fetal acidosis phase, defined as the time from the second LPS injection until intrauterine fetal death. Histological examinations of the fetal membrane and umbilical cord were also conducted.

RESULTS

Each fetus developed metabolic acidosis after the second injection of LPS. The fetuses died 24.7 (SD = 6.1) hours after the second injection of LPS. Both the umbilical cord and fetal membranes showed histological evidence of severe inflammation. In total, 163 fetal baroreceptor measurements were performed in this experiment (A, n = 77 times; B, n = 60 times; C, n = 26 times). Fetal baroreceptor sensitivity showed significant differences in all three phases (A: 2.7 [SD = 0.2]; B: 2.5 [SD = 0.2]; and C: 1.5 [SD = 0.2]). Post hoc tests showed that baroreceptor sensitivity in the acidosis phase had decreased significantly compared to that in the control and acute phases (p<.001 and p=.002, respectively).

CONCLUSIONS

Fetal baroreceptor sensitivity decreased during fetal acidosis induced by LPSs.

An Update of Our Understanding of Fetal Heart Rate Patterns in Health and Disease

UNDERSTANDING FETAL HEART RATE PATTERNS THAT MAY PREDICT ANTENATAL AND INTRAPARTUM NEURAL INJURY: Christopher A. Lear, Jenny A. Westgate, Austin Ugwumadu, Jan G. Nijhuis, Peter R. Stone, Antoniya Georgieva, Tomoaki Ikeda, Guido Wassink , Laura Bennet , Alistair J. Gunn Seminars in Pediatric Neurology Volume 28, December 2018, Pages 3-16 Electronic fetal heart rate (FHR) monitoring is widely used to assess fetal well-being throughout pregnancy and labor. Both antenatal and intrapartum FHR monitoring are associated with a high negative predictive value and a very poor positive predictive value. This in part reflects the physiological resilience of the healthy fetus and the remarkable effectiveness of fetal adaptations to even severe challenges. In this way, the majority of "abnormal" FHR patterns in fact reflect a fetus' appropriate adaptive responses to adverse in utero conditions. Understanding the physiology of these adaptations, how they are reflected in the FHR trace and in what conditions they can fail is therefore critical to appreciating both the potential uses and limitations of electronic FHR monitoring.

Fetal defenses against intrapartum head compression-implications for intrapartum decelerations and hypoxic-ischemic injury

Uterine contractions during labor and engagement of the fetus in the birth canal can compress the fetal head. Its impact on the fetus is unclear and still controversial. In this integrative physiological review, we highlight evidence that decelerations are uncommonly associated with fetal head compression. Next, the fetus has an impressive ability to adapt to increased intracranial pressure through activation of the intracranial baroreflex, such that fetal cerebral perfusion is well-maintained during labor, except in the setting of prolonged systemic hypoxemia leading to secondary cardiovascular compromise. Thus, when it occurs, fetal head compression is not necessarily benign but does not seem to be a common contributor to intrapartum decelerations. Finally, the intracranial baroreflex and the peripheral chemoreflex (the response to acute hypoxemia) have overlapping efferent effects. We propose the hypothesis that these reflexes may work synergistically to promote fetal adaptation to labor.

Dissecting the contributions of the peripheral chemoreflex and myocardial hypoxia to fetal heart rate decelerations in near-term fetal sheep

Brief repeated fetal hypoxaemia during labour can trigger intrapartum decelerations of the fetal heart rate (FHR) via the peripheral chemoreflex or the direct effects of myocardial hypoxia, but the relative contribution of these two mechanisms and how this balance changes with evolving fetal compromise remain unknown. In the present study, chronically instrumented near-term fetal sheep received surgical vagotomy (n = 8) or sham vagotomy (control, n = 11) to disable the peripheral chemoreflex and unmask myocardial hypoxia. One-minute complete umbilical cord occlusions (UCOs) were performed every 2.5 min for 4 h or until arterial pressure fell below 20 mmHg. Hypotension and severe acidaemia developed progressively after 65.7 ± 7.2 UCOs in control fetuses and 49.5 ± 7.8 UCOs after vagotomy. Vagotomy was associated with faster development of metabolic acidaemia and faster impairment of arterial pressure during UCOs without impairing centralization of blood flow or neurophysiological adaptation to UCOs. During the first half of the UCO series, before severe hypotension developed, vagotomy was associated with a marked increase in FHR during UCOs. After the onset of evolving severe hypotension, FHR fell faster in control fetuses during the first 20 s of UCOs, but FHR during the final 40 s of UCOs became progressively more similar between groups, with no difference in the nadir of decelerations. In conclusion, FHR decelerations were initiated and sustained by the peripheral chemoreflex at a time when fetuses were able to maintain arterial pressure. After the onset of evolving hypotension and acidaemia, the peripheral chemoreflex continued to initiate decelerations, but myocardial hypoxia became progressively more important in sustaining and deepening decelerations. KEY POINTS: Brief repeated hypoxaemia during labour can trigger fetal heart rate decelerations by either the peripheral chemoreflex or myocardial hypoxia, but how this balance changes with fetal compromise is unknown. Reflex control of fetal heart rate was disabled by vagotomy to unmask the effects of myocardial hypoxia in chronically instrumented fetal sheep. Fetuses were then subjected to repeated brief hypoxaemia consistent with the rates of uterine contractions during labour. We show that the peripheral chemoreflex controls brief decelerations in their entirety at a time when fetuses were able to maintain normal or increased arterial pressure. The peripheral chemoreflex still initiated decelerations even after the onset of evolving hypotension and acidaemia, but myocardial hypoxia made an increasing contribution to sustain and deepen decelerations.

Does a physiology-based interpretation of cardiotocography allow to dispense with second-line methods? A cross-sectional online survey

CONTEXT

Second line methods are used to help obstetricians to identify abnormalities that reflect fetal acidosis. Since the use of a new technique of cardiotocography (CTG) interpretation based on the pathophysiology of the fetal period, the use of second-line tests has been questioned.

OBJECTIVE

To evaluate the impact of specific training in CTG physiology-based interpretation on professional attitudes towards the use of second-line methods.

METHODS

This cross-sectional study included 57 French obstetricians divided into two groups: the trained group (obstetricians who had already participated in a training course in physiology-based interpretation of CTG) and the control group. Ten medical records of patients who had abnormal CTG tracings and underwent fetal blood sampling pH measurement during labour were presented to the participants. They were given three choices: use a second-line method, continue labour without using second-line method, or perform a caesarean section. The main outcome measures was the median number of decisions to use second-line method.

RESULTS

Forty participants were included in the trained group and 17 in the control group. The median number of recourses to second-line method was significantly inferior for the trained group (4/10 second-line methods) than for the control group (6/10, p=0.040). Regarding the 4 records for which a caesarean section was the real outcome, the median number of decisions of continuing labour was significantly superior in the trained group than in the control group (p=0.032).

CONCLUSIONS

Participation in a training course in physiology-based interpretation of CTG could be associated with a less frequent use of second-line method at the cost of more frequently continuing labour with the risk compromising fetal and maternal well-being. Additional studies are required to determine whether this change in attitude is safe for the fetal well-being.

Fetal heart rate responses in chronic hypoxaemia with superimposed repeated hypoxaemia consistent with early labour: a controlled study in fetal sheep

OBJECTIVE

Deceleration area (DA) and capacity (DC) of the fetal heart rate can help predict risk of intrapartum fetal compromise. However, their predictive value in higher risk pregnancies is unclear. We investigated whether they can predict the onset of hypotension during brief hypoxaemia repeated at a rate consistent with early labour in fetal sheep with pre-existing hypoxaemia.

DESIGN

Prospective, controlled study.

SETTING

Laboratory.

SAMPLE

Chronically instrumented, unanaesthetised near-term fetal sheep.

METHODS

One-minute complete umbilical cord occlusions (UCOs) were performed every 5 minutes in fetal sheep with baseline p_a O₂ <17 mmHg (hypoxaemic, n = 8) and >17 mmHg (normoxic, n = 11) for 4 hours or until arterial pressure fell <20 mmHg.

MAIN OUTCOME MEASURES

DA, DC and arterial pressure.

RESULTS

Normoxic fetuses showed effective cardiovascular adaptation without hypotension and mild acidaemia (lowest arterial pressure 40.7 ± 2.8 mmHg, pH 7.35 ± 0.03). Hypoxaemic fetuses developed hypotension (lowest arterial pressure 20.8 ± 1.9 mmHg, P < 0.001) and acidaemia (final pH 7.07 ± 0.05). In hypoxaemic fetuses, decelerations showed faster falls in FHR over the first 40 seconds of UCOs but the final deceleration depth was not different to normoxic fetuses. DC was modestly higher in hypoxaemic fetuses during the penultimate (P = 0.04) and final (P = 0.012) 20 minutes of UCOs. DA was not different between groups.

CONCLUSION

Chronically hypoxaemic fetuses had early onset of cardiovascular compromise during labour-like brief repeated UCOs. DA was unable to identify developing hypotension in this setting, while DC only showed modest differences between groups. These findings highlight that DA and DC thresholds need to be adjusted for antenatal risk factors, potentially limiting their clinical utility.

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

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.

Is It Time to Redefine Fetal Decelerations in Cardiotocography?

Historically, fetal heart rate (FHR) decelerations were classified into “early”, “late”, and “variable” based on their relationship with uterine contractions. So far, three different putative etiologies were taken for granted. Recently, this belief, passed down through generations of birth attendants, has been questioned by physiologists. This narrative review aimed to assess the evidence on pathophysiology behind intrapartum FHR decelerations. This narrative review is based on information sourced from online peer-reviewed articles databases and recommendations from the major scientific societies in the field of obstetrics. Searches were performed in MEDLINE/PubMed, EMBASE, and Scopus and selection criteria included studies in animals and humans, where the physiology behind FHR decelerations was explored. The greater affinity for oxygen of fetal hemoglobin than the maternal, the unicity of fetal circulation, and the high anaerobic reserve of the myocardium, ensure adequate oxygenation to the fetus, under basal conditions. During acute hypoxic stress the efficiency of these mechanisms are increased because of the peripheral chemoreflex. This reflex, activated at each uterine contraction, is characterized by the simultaneous activation of two neural arms: the parasympathetic arm, which reduces the myocardial consumption of oxygen by decreasing the FHR and the sympathetic component, which promotes an intense peripheric vasoconstriction, thus centralizing the fetal blood volume. This review summarizes the evidence supporting the hypoxic origin of FHR decelerations, therefore archiving the historical belief that FHR decelerations have different etiologies, according to their shape and relationship with uterine contractions. The present review suggests that it is time to welcome the new scientific evidence and to update the CTG classification systems.

Variable deceleration features and intrapartum fetal acidemia - The role of deceleration area

OBJECTIVE

In recent years deceleration area has received increasing attention as a potential predictor of intrapartum fetal hypoxia. In several studies, the area has been manually esteemed as triangular in shape, which might introduce bias. In addition, the commonly used outcome acidemia in umbilical artery is affected by mode of delivery. We wanted to investigate the association between the variable deceleration features area, duration, depth and cumulative deceleration area (30 and 60 min) and intrapartum fetal acidemia measured as lactate concentration at fetal scalp blood sampling (FBS) in immediate connection to the decelerations.

STUDY DESIGN

In the source population of 1070 labors at Karolinska University Hospital, Sweden, with FBS performed on indication, we found 507 fetuses with predominantly variable decelerations as the indication for FBS. We examined the last 60- and 30-minutes of fetal monitoring preceding the FBS with focus on deceleration area, duration and depth. The contours of the decelerations were outlined manually but the area was calculated with a computer software program. We assessed area, duration and depth both as mean values per deceleration and as cumulative values during the time period of interest. We analyzed Pearson correlations and area under receiver operating characteristics curves (AUC). We also performed an adjusted analysis, with baseline frequency, variability, and accelerations as covariates.

RESULTS

Deceleration area and duration were the best predictors of intrapartum fetal acidemia (fetal lactate concentration >4.8 mmol/L measured with Lactate Pro™) with AUCs of 0.671 (0.682) and 0.678 (0.683) for cumulative measures during 30 (60) minutes prior to FBS, compared to deceleration depth with AUC of 0.632 (0.631). Corresponding Pearson correlations in 30-min (60-min) groups were 0.329 (0.335) and 0.358 (0.354) for deceleration area and duration and 0.212 (0.204) for deceleration depth. Using 250 beats cumulative cut-off for deceleration area during last 30 min, 71% vs. 43% were acidemic and non-acidemic, odds ratio = 3.2 (95% CI 1.7-6.1).

CONCLUSIONS

Deceleration area and duration were better predictors of intrapartum fetal acidemia than deceleration depth. Cumulative deceleration area >250 beats during 30 min was associated with three-fold higher odds of intrapartum acidemia compared to <250 beats.

Roles of parasympathetic outflow and sympathetic outflow in the cardiovascular response to brief umbilical cord occlusion in fetal sheep

Fetal heart rate (FHR) deceleration is the most common change seen during labor. The role of the autonomic nervous system in regulating the fetal cardiovascular response during multiple uterine contractions has been well-established. However, the mechanism underlying the hemodynamic response remains unclear and the specific reflex that mediates the cardiovascular modifications is still controversial. This study aimed to determine the role of the sympathetic and parasympathetic systems on fetal hemodynamics in complete cord occlusion. Chronically instrumented fetal sheep were randomized to receive an intravenous injection of atropine 2.5 mg (n = 8), propranolol 5 mg (n = 7), atropine and propranolol (n = 7), or a control protocol (n = 9), followed by three episodes of 1-minute umbilical cord occlusion repeated every 5 minutes. Cord compression induces a rapid decrease in the FHR and a rapid increase in MAP. The decrease in FHR is caused by an increase in parasympathetic activity, (atropine and atropine-propranolol abolish the FHR response to the occlusion). The change in FHR during occlusion was not modified by propranolol injection, showing no effect of sympathetic tone. The increase in MAP during occlusion was similar in the four protocols. After releasing occlusion, the FHR was still lower than that at baseline due to a sustained parasympathetic tone. Suppression of the parasympathetic output to the cardiovascular system unmasks an increase in the FHR above baseline values. The lower FHR with the propranolol protocol further supports an increase in myocardial β-adrenoceptor stimulation after cord release. The increase in MAP after cord release was similar in the four protocols, except after the early stage of interocclusion period in atropine protocol. Four minutes after cord release, the FHR returned to baseline irrespective of the drugs that were infused, thereby showing recovery of ANS control. Blood gases (pH, PaCO2, PaO2) and plasma lactate concentrations was similar between the four protocols at the end of three applications of UCO. Complete cord compression-induced deceleration is likely due to acute activation of parasympathetic output. β-adrenoceptor activity is involved in the increase in FHR after cord release. Understanding the reflexes involved in FHR deceleration may help us understand the mechanisms underlying fetal autonomic adaptation during cord occlusion.

Characteristics and physiological basis of falls in ventricular outputs after immediate cord clamping at delivery in preterm fetal lambs

KEY POINTS

Controversy exists about the physiological mechanism(s) underlying decreases in cardiac output after immediate clamping of the umbilical cord at birth. To define these mechanisms, the four major determinants of ventricular output (afterload, preload, heart rate and contractility) were measured concurrently in fetal lambs at 15 s intervals over a 2 min period after cord clamping and before ventilation following delivery. After cord clamping, right (but not left) ventricular output fell by 20% in the initial 30 s, due to increased afterload associated with higher arterial blood pressures, but both outputs then halved over 45 s, due to a falling heart rate and deteriorating ventricular contractility accompanying rapid declines in arterial oxygenation to asphyxial levels. Ventricular outputs subsequently plateaued from 75 to 120 s, associated with rebound rises in ventricular contractility accompanying asphyxia-induced surges in circulating catecholamines. These findings provide a physiological basis for the clinical recommendation that effective ventilation should occur within 60 s after immediate cord clamping.

ABSTRACT

Controversy exists about the physiological mechanism(s) underlying large decreases in cardiac output after immediate clamping of the umbilical cord at birth. To define these mechanisms, anaesthetized preterm fetal lambs (127(1)d, n = 12) were instrumented with flow probes and catheters in major central arteries, and a left ventricular (LV) micromanometer-conductance catheter. Following immediate cord clamping at delivery, haemodynamics, LV and right ventricular (RV) outputs, and LV contractility were measured at 15 s intervals during a 2 min non-ventilatory period, with aortic blood gases and circulating catecholamine (noradrenaline and adrenaline) concentrations measured at 30 s intervals. After cord clamping, (1) RV (but not LV) output fell by 20% in the initial 30 s, due to a reduced stroke volume associated with increased arterial blood pressures, (2) both outputs then halved over the next 45 s, associated with falls in heart rate, arterial blood pressures and ventricular contractility accompanying a rapid decline in arterial oxygenation to asphyxial levels, (3) reduced outputs subsequently plateaued from 75 to 120 s, associated with rebound rises in blood pressures and ventricular contractility accompanying exponential surges in circulating catecholamines. These findings are consistent with a time-dependent decline of ventricular outputs after immediate cord clamping, which comprised (1) an initial, minor fall in RV output related to altered loading conditions, (2) ensuing large decreases in both LV and RV outputs related to the combination of bradycardia and ventricular dysfunction during emergence of an asphyxial state, and (3) subsequent stabilization of reduced LV and RV outputs during ongoing asphyxia, supported by cardiovascular stimulatory effects of marked sympathoadrenal activation.

Transient effects of forebrain ischemia on fetal heart rate variability in fetal sheep

Fetal heart rate variability (FHRV) is a key index of antenatal and intrapartum fetal well-being. FHRV is well established to be mediated by both arms of the autonomic nervous system, but it remains unknown whether higher centers in the forebrain contribute to FHRV. We tested the hypothesis that selective forebrain ischemia would impair the generation of FHRV. Sixteen chronically instrumented near-term fetal sheep were subjected to either forebrain ischemia induced by bilateral carotid occlusion or sham-ischemia for 30 min. Time, frequency, and nonlinear measures of FHRV were assessed during and for seven days after ischemia. Ischemia was associated with profound suppression of electroencephalographic (EEG) power, which remained suppressed throughout the recovery period (P < 0.001). During the first 5 min of ischemia, multiple time and frequency domain measures were increased (all P < 0.05) before returning back to sham levels. A delayed increase in sample entropy was observed during ischemia (P < 0.05). For the first 3 h after ischemia, there was moderate suppression of two measures of FHRV (very-low frequency power and the standard deviation of RR-intervals, both P < 0.05) and increased sample entropy (P < 0.05). Thereafter, all measures of FHRV returned to control levels. In conclusion, profound forebrain ischemia sufficient to lead to severe neural injury had only transient effect on multiple measures of FHRV. These findings suggest that the forebrain makes a limited contribution to FHRV. FHRV therefore primarily originates in the hindbrain and is unlikely to provide meaningful information on forebrain neurodevelopment or metabolism.

Lack of evidence for impaired preload or Bezold-Jarisch activation during brief umbilical cord occlusions in fetal sheep

Impaired cardiac preload secondary to umbilical cord occlusion (UCO) has been hypothesized to contribute to intrapartum decelerations, brief falls in fetal heart rate (FHR), through activation of the Bezold-Jarisch reflex. This cardioprotective reflex increases parasympathetic and inhibits sympathetic outflows triggering hypotension, bradycardia, and peripheral vasodilation, but its potential to contribute to intrapartum decelerations has never been systematically examined. In this study, we performed bilateral cervical vagotomy to remove the afferent arm and the efferent parasympathetic arm of the Bezold-Jarisch reflex. Twenty-two chronically instrumented fetal sheep at 0.85 of gestation received vagotomy (n = 7) or sham vagotomy (control, n = 15), followed by three 1-min complete UCOs separated by 4-min reperfusion periods. UCOs in control fetuses were associated with a rapid fall in FHR and reduced femoral blood flow mediated by intense femoral vasoconstriction, leading to hypertension. Vagotomy abolished the rapid fall in FHR (P < 0.001) and, despite reduced diastolic filling time, increased both carotid (P < 0.001) and femoral (P < 0.05) blood flow during UCOs, secondary to carotid vasodilation (P < 0.01) and delayed femoral vasoconstriction (P < 0.05). Finally, vagotomy was associated with an attenuated rise in cortical impedance during UCOs (P < 0.05), consistent with improved cerebral substrate supply. In conclusion, increased carotid and femoral blood flows after vagotomy are consistent with increased left and right ventricular output, which is incompatible with the hypothesis that labor-like UCOs impair ventricular filling. Overall, the cardiovascular responses to vagotomy do not support the hypothesis that the Bezold-Jarisch reflex is activated by UCO. The Bezold-Jarisch reflex is therefore mechanistically unable to contribute to intrapartum decelerations.

Deceleration area and capacity during labour-like umbilical cord occlusions identify evolving hypotension: a controlled study in fetal sheep

OBJECTIVE

Cardiotocography is widely used to assess fetal well-being during labour. The positive predictive value of current clinical algorithms to identify hypoxia-ischaemia is poor. In experimental studies, fetal hypotension is the strongest predictor of hypoxic-ischaemic injury. Cohort studies suggest that deceleration area and deceleration capacity of the fetal heart rate trace correlate with fetal acidaemia, but it is not known whether they are indices of fetal arterial hypotension.

DESIGN

Prospective, controlled study.

SETTING

Laboratory.

SAMPLE

Near-term fetal sheep.

METHODS

One minute of complete umbilical cord occlusions (UCOs) every 5 minutes (1:5 min, n = 6) or every 2.5 minutes (1:2.5 min, n = 12) for 4 hours or until fetal mean arterial blood pressure fell <20 mmHg.

MAIN OUTCOME MEASURES

Deceleration area and capacity during the UCO series were related to evolving hypotension.

RESULTS

The 1:5 min group developed only mild metabolic acidaemia, without hypotension. By contrast, 10/12 fetuses in the 1:2.5-min group progressively developed severe metabolic acidaemia and hypotension, reaching 16.8 ± 0.9 mmHg after 71.2 ± 6.7 UCOs. Deceleration area and capacity remained unchanged throughout the UCO series in the 1:5-min group, but progressively increased in the 1:2.5-min group. The severity of hypotension was closely correlated with both deceleration area (P < 0.001, R²  = 0.66, n = 18) and capacity (P < 0.001, R²  = 0.67, n = 18). Deceleration area and capacity predicted development of hypotension at a median of 103 and 123 minutes before the final occlusion, respectively.

CONCLUSIONS

Both deceleration area and capacity were strongly associated with developing fetal hypotension, supporting their potential to improve identification of fetuses at risk of hypotension leading to hypoxic-ischaemic injury during labour.

TWEETABLE ABSTRACT

Deceleration area and capacity of fetal heart rate identify developing hypotension during labour-like hypoxia.

"The First Thousand Days" Define a Fetal/Neonatal Neurology Program

Gene-environment interactions begin at conception to influence maternal/placental/fetal triads, neonates, and children with short- and long-term effects on brain development. Life-long developmental neuroplasticity more likely results during critical/sensitive periods of brain maturation over these first 1,000 days. A fetal/neonatal program (FNNP) applying this perspective better identifies trimester-specific mechanisms affecting the maternal/placental/fetal (MPF) triad, expressed as brain malformations and destructive lesions. Maladaptive MPF triad interactions impair progenitor neuronal/glial populations within transient embryonic/fetal brain structures by processes such as maternal immune activation. Destructive fetal brain lesions later in pregnancy result from ischemic placental syndromes associated with the great obstetrical syndromes. Trimester-specific MPF triad diseases may negatively impact labor and delivery outcomes. Neonatal neurocritical care addresses the symptomatic minority who express the great neonatal neurological syndromes: encephalopathy, seizures, stroke, and encephalopathy of prematurity. The asymptomatic majority present with neurologic disorders before 2 years of age without prior detection. The developmental principle of ontogenetic adaptation helps guide the diagnostic process during the first 1,000 days to identify more phenotypes using systems-biology analyses. This strategy will foster innovative interdisciplinary diagnostic/therapeutic pathways, educational curricula, and research agenda among multiple FNNP. Effective early-life diagnostic/therapeutic programs will help reduce neurologic disease burden across the lifespan and successive generations.

Fetal physiology cardiotocography training, a regional evaluation

INTRODUCTION

Cardiotocography (CTG) has its limits in detecting fetal acidosis and intrapartum asphyxia. Our aim was to evaluate a CTG training programme based on fetal physiology in the Mediterranean perinatal network.

METHODS

Professionals from 41 maternity units of the Mediterranean network were invited to participate in a CTG masterclass based on fetal physiology in March 2019 and October 2019. They were asked to react to three practical cases by a physiological approach before the training course (T0), one month after (T1) and six to seven months after (T2). The mean scores were compared by using a mixed model including lapse of time to evaluation, profession of participants and level of the maternity unit as fixed effects.

RESULTS

A total of 248 professionals from 32 maternity units finally participated in the organizational audit. By using a mixed model, we found a significant improvement of the mean score at T1=6.44/10 compared to T0=4.97/10 (p<0.0001), and a significant improvement of the mean score obtained at T2=6.17/10 compared to T0 (p<0.0001). T2 scores were not significantly different from T1 scores (p=0.143).

DISCUSSION

A CTG training programme based on fetal physiology showed a significant improvement in the professionals' interpretation of CTG at short term and stable results at long term. Continuing medical education could help maintain and improve knowledge to ensure neonatal safety.

Effects of antenatal dexamethasone and hyperglycemia on cardiovascular adaptation to asphyxia in preterm fetal sheep

Antenatal glucocorticoids improve outcomes among premature infants but are associated with hyperglycemia, which can exacerbate hypoxic-ischemic injury. It is still unclear how antenatal glucocorticoids or hyperglycemia modulate fetal cardiovascular adaptations to severe asphyxia. In this study, preterm fetal sheep received either saline or 12 mg im maternal dexamethasone, followed 4 h later by complete umbilical cord occlusion (UCO) for 25 min. An additional cohort of fetuses received titrated glucose infusions followed 4 h later by UCO to control for the possibility that hyperglycemia contributed to the cardiovascular effects of dexamethasone. Fetuses were studied for 7 days after UCO. Maternal dexamethasone was associated with fetal hyperglycemia (P < 0.001), increased arterial pressure (P < 0.001), and reduced femoral (P < 0.005) and carotid (P < 0.05) vascular conductance before UCO. UCO was associated with bradycardia, femoral vasoconstriction, and transient hypertension. For the first 5 min of UCO, fetal blood pressure in the dexamethasone-asphyxia group was greater than saline-asphyxia (P < 0.001). However, the relative increase in arterial pressure was not different from saline-asphyxia. Fetal heart rate and femoral vascular conductance fell to similar nadirs in both saline and dexamethasone-asphyxia groups. Dexamethasone did not affect the progressive decline in femoral vascular tone or arterial pressure during continuing UCO. By contrast, there were no effects of glucose infusions on the response to UCO. In summary, maternal dexamethasone but not fetal hyperglycemia increased fetal arterial pressure before and for the first 5 min of prolonged UCO but did not augment the cardiovascular adaptations to acute asphyxia.

Parasympathetic activity is the key regulator of heart rate variability between decelerations during brief repeated umbilical cord occlusions in fetal sheep

Fetal heart rate variability (FHRV) is a widely used index of intrapartum well being. Both arms of the autonomic system regulate FHRV under normoxic conditions in the antenatal period. However, autonomic control of FHRV during labor when the fetus is exposed to repeated, brief hypoxemia during uterine contractions is poorly understood. We have previously shown that the sympathetic nervous system (SNS) does not regulate FHRV during labor-like hypoxia. We therefore investigated the hypothesis that the parasympathetic system is the main mediator of intrapartum FHRV. Twenty-six chronically instrumented fetal sheep at 0.85 of gestation received either bilateral cervical vagotomy (n = 7), atropine sulfate (n = 7), or sham treatment (control, n = 12), followed by three 1-min complete umbilical cord occlusions (UCOs) separated by 4-min reperfusion periods. Parasympathetic blockade reduced three measures of FHRV before UCOs (all P < 0.01). Between UCOs, atropine and vagotomy were associated with marked tachycardia (both P < 0.005), suppressed measures of FHRV (all P < 0.01), and abolished FHRV on visual inspection compared with the control group. Tachycardia in the atropine and vagotomy groups resolved over the first 10 min after the final UCO, in association with evidence that the SNS contribution to FHRV progressively returned during this time. Our findings support that SNS control of FHRV is acutely suppressed for at least 4 min after a deep intrapartum deceleration and takes 5-10 min to recover. The parasympathetic system is therefore likely to be the key mediator of FHRV once frequent FHR decelerations are established during labor.

Effects of β-adrenergic stimulation on fetal heart rate, heart rate variability, and T-wave elevation during brief umbilical cord occlusions in fetal sheep

Circulating catecholamines are critical for fetal adaptation to hypoxia by regulating fetal heart rate (FHR) and promoting myocardial contractility and peripheral vasoconstriction. They have been hypothesized to contribute to changes in FHR variability (FHRV) and T-wave morphology, clinical indexes of fetal well-being during labor. β-Adrenergic blockade with propranolol does not affect FHRV during labor-like hypoxemia and only attenuated the increase in T-wave height between the episodes of hypoxemia. To further investigate the potential role of catecholamines, we investigated whether pharmacological β-adrenergic stimulation could increase FHRV and T-wave elevation during intermittent labor-like hypoxemia. Nineteen chronically instrumented fetal sheep at 0.85 of gestation received isoprenaline hydrochloride (n = 7) or saline (control, n = 12), followed by three 1-min complete umbilical cord occlusions (UCOs) separated by 4-min reperfusion periods. Before the UCOs, infusion of isoprenaline increased FHR (P < 0.001), absolute-T/QRS ratio (P < 0.001), and one measure of FHRV [root-mean-square of successive RR interval differences (RMSSD), P < 0.05]. UCOs triggered deep FHR decelerations. During UCOs, isoprenaline was associated with increased FHR (P < 0.001) and absolute-T/QRS ratio (P < 0.05), but no effect on T/QRS ratio was observed when normalized to baseline before UCOs (normalized-T/QRS ratio). Between UCOs, isoprenaline increased FHR (P < 0.001) and absolute-T/QRS ratio (P < 0.05) but did not affect normalized-T/QRS ratio or any measures of FHRV. Arterial pressure was not affected by isoprenaline at any point. Our findings indicate that circulating catecholamines regulate FHR but not FHRV during labor-like hypoxemia and promote T-wave elevation between but not during intermittent fetal hypoxemia.