Cerebrovascular response to maternal hyperoxygenation in fetuses with hypoplastic left heart syndrome depends on gestational age and baseline cerebrovascular resistance

Safety and feasibility pilot study of continuous low-dose maternal supplemental oxygen in fetal single ventricle heart disease

OBJECTIVE

Fetuses with single ventricle physiology (SVP) exhibit reductions in fetal cerebral oxygenation, with associated delays in fetal brain growth and neurodevelopmental outcomes. Maternal supplemental oxygen (MSO) has been proposed to improve fetal brain growth, but current evidence on dosing, candidacy and outcomes is limited. In this pilot study, we evaluated the safety and feasibility of continuous low-dose MSO in the setting of SVP.

METHODS

This single-center, open-label, pilot phase-1 safety and feasibility clinical trial included 25 pregnant individuals with a diagnosis of fetal SVP. Participants self-administered continuous MSO using medical-grade oxygen concentrators for up to 24 h per day from the second half of gestation until delivery. The primary aim was the evaluation of the safety profile and feasibility of MSO. A secondary preliminary analysis was performed to assess the impact of MSO on the fetal circulation using echocardiography and late-gestation cardiovascular magnetic resonance imaging. Early outcomes were assessed, including perinatal growth and preoperative brain injury, and neurodevelopmental outcomes were assessed at 18 months using the Bayley Scales of Infant and Toddler Development 3rd edition, and compared with those of a contemporary fetal SVP cohort (n = 217) that received the normal standard of care (SOC).

RESULTS

Among the 25 participants, the median maternal age at conception was 35 years, and fetal SVP diagnoses included 16 with right ventricle dominant, eight with left ventricle dominant and one with indeterminate ventricular morphology. Participants started the trial at approximately 29 + 2 weeks' gestation and self-administered MSO for a median of 16.1 h per day for 63 days, accumulating a median of 1029 h of oxygen intake from enrolment until delivery. The only treatment-associated adverse events were nasal complications that were resolved typically by attaching a humidifier unit to the oxygen concentrator. No premature closure of the ductus arteriosus or unexpected fetal demise was observed. In the secondary analysis, MSO was not associated with any changes in fetal growth, middle cerebral artery pulsatility index, cerebroplacental ratio or head-circumference-to-abdominal-circumference ratio Z-scores over gestation compared with SOC. Although MSO was associated with changes in umbilical artery pulsatility index Z-score over the study period compared with SOC (P = 0.02), this was probably due to initial baseline differences in placental resistance. At late-gestation cardiovascular magnetic resonance imaging, MSO was not associated with an increase in fetal cerebral oxygen delivery. Similarly, no differences were observed in neonatal outcomes, including preoperative brain weight Z-score and brain injury, mortality by 18 months of age and neurodevelopmental outcomes at 18 months of age.

CONCLUSIONS

This pilot phase-1 clinical trial indicates that low-dose MSO therapy is safe and well tolerated in pregnancies diagnosed with fetal SVP. However, our protocol was not associated with an increase in fetal cerebral oxygen delivery or improvements in early neurological or neurodevelopmental outcomes. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Non-invasive in-utero quantification of vascular reactivity in human placenta

OBJECTIVE

Placental vascular reactivity (PlVR) indicates the ability of the placental vasculature to match blood supply to fetal demand. Many pregnancy disorders alter the characteristics of PlVR, resulting in suboptimal oxygen delivery, although current understanding is limited by the lack of non-invasive, repeatable methods to measure PlVR in utero. Our objective was to quantify PlVR by measuring the placental response to transient changes in maternal carbon dioxide (CO2) using blood-oxygen-level-dependent (BOLD) magnetic resonance imaging (MRI). We hypothesized that PlVR will increase with gestational age to meet the changing demands of a growing fetus, and that PlVR will be driven by a maternal response to changes in CO2 concentration.

METHODS

This was a cross-sectional study of 35 women with a healthy singleton pregnancy, of whom 31 were included in the analysis. The median gestational age was 32.6 (range, 22.6-38.4) weeks. Pregnant women were instructed to follow audiovisual breathing cues during a MRI scan. Maternal end-tidal CO2 (EtCO2) was measured concurrently with resting placental BOLD MRI for a total of 7-8 min. Preprocessing of magnetic resonance images consisted of manual delineation of placental anatomy and motion correction. In each placental voxel, vascular reactivity was computed using a coherence-weighted general linear model between MRI signal and EtCO2 stimulus. Global PlVR was computed as the mean of voxel-wise PlVR values across the placenta.

RESULTS

PlVR, quantified by the placental response to induced, transient changes in maternal CO2, was consistently measured in utero using BOLD MRI. PlVR increased non-linearly with advancing gestational age (P < 0.001) and was higher on the fetal side of the placenta. PlVR was associated positively with fetal brain volume after accounting for gestational age. PlVR did not show any significant associations with maternal characteristics.

CONCLUSIONS

We present, for the first time, a non-invasive paradigm to quantify PlVR in ongoing human pregnancies without the use of exogenous gases or contrast agents. Our findings suggest that PlVR is driven by a fetal response to changes in maternal CO2. Ease of translation to the clinical setting makes PlVR a promising biomarker for the identification and management of high-risk pregnancies. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Impaired Maternal-Fetal Environment and Risk for Preoperative Focal White Matter Injury in Neonates With Complex Congenital Heart Disease

Background Infants with congenital heart disease (CHD) are at risk for white matter injury (WMI) before neonatal heart surgery. Better knowledge of the causes of preoperative WMI may provide insights into interventions that improve neurodevelopmental outcomes in these patients. Methods and Results A prospective single-center study of preoperative WMI in neonates with CHD recorded data on primary cardiac diagnosis, maternal-fetal environment (MFE), delivery type, subject anthropometrics, and preoperative care. Total maturation score and WMI were assessed, and stepwise logistic regression modeling selected risk factors for WMI. Among subjects with severe CHD (n=183) who received a preoperative brain magnetic resonance imaging, WMI occurred in 40 (21.9%) patients. WMI prevalence (21.4%-22.1%) and mean volumes (119.7-160.4 mm3) were similar across CHD diagnoses. Stepwise logistic regression selected impaired MFE (odds ratio [OR], 2.85 [95% CI, 1.29-6.30]), male sex (OR, 2.27 [95% CI, 1.03-5.36]), and older age at surgery/magnetic resonance imaging (OR, 1.20 per day [95% CI, 1.03-1.41]) as risk factors for preoperative WMI and higher total maturation score values (OR, 0.65 per unit increase [95% CI, 0.43-0.95]) as protective. A quarter (24.6%; n=45) of subjects had ≥1 components of impaired MFE (gestational diabetes [n=12; 6.6%], gestational hypertension [n=11; 6.0%], preeclampsia [n=2; 1.1%], tobacco use [n=9; 4.9%], hypothyroidism [n=6; 3.3%], and other [n=16; 8.7%]). In a subset of 138 subjects, an exploratory analysis of additional MFE-related factors disclosed other potential risk factors for WMI. Conclusions This study is the first to identify impaired MFE as an important risk factor for preoperative WMI. Vulnerability to preoperative WMI was shared across CHD diagnoses.

Narrative review of single ventricle: where are we after 40 years?

BACKGROUND AND OBJECTIVE

Key medical and surgical advances have been made in the longitudinal management of patients with "functionally" single ventricle physiology, with the principles of Fontan circulation applied to other complex congenital heart defects. The purpose of this article is to review all of the innovations, starting from fetal life, that led to a change of strategy for single ventricle.

METHODS

Our literature review included all full articles published in English language on the Cochrane, MedLine, and Embase with references to "single ventricle" and "univentricular hearts", including the initial history of the treatments for this congenital heart defects as well as the innovations reported within the last decades.

KEY CONTENT AND FINDINGS

All innovations introduced have been analyzed, including: (I) fetal diagnosis and interventions, in particular to prevent or reduce brain damages; (II) neonatal care; (III) post-natal diagnosis; (IV) interventional cardiology procedures; (V) surgical procedures, including neonatal palliations, hybrid procedures, bidirectional Glenn and variations, Fontan completion, biventricular repair; (VI) peri-operative management; (VII) Fontan failure, with Fontan take-down and conversion, and mechanical circulatory support; (VIII) transplantation, including heart, heart and lung, heart and liver; (IX) exercise; (X) pregnancy; (XI) adolescents and adults without Fontan completion; (XII) future studies, including experimental studies on animals, computational studies, genetics, stem cells and bioengineering.

CONCLUSIONS

These last 40 years have certainly changed the course of natural history for children born with any form of "functionally" single ventricle, thanks to the improvement in diagnostic and treatment techniques, and particularly to the increased knowledge of the morphology and function of these complex hearts, from fetal to adult life. There is still much left unexplored and room for improvement, and all efforts should be concentrated in collaborations among different institutions and specialties, focused on the same matter.

Maternal hyperoxygenation during pregnancy as a tool in fetal disease diagnosis and treatment

Maternal hyperoxygenation (MHO) consists of giving pregnant women (60% to 100%) oxygen through a facemask and using ultrasound assess or monitor the influence on fetal cardiovascular circulation. This review discusses the findings and the utility of acute and chronic MHO in various fetal diseases.

Care of the Fetus With Congenital Cardiovascular Disease: From Diagnosis to Delivery

BACKGROUND

The majority of congenital cardiovascular disease including structural cardiac defects, abnormalities in cardiac function, and rhythm disturbances can be identified prenatally using screening obstetrical ultrasound with referral for fetal echocardiogram when indicated.

METHODS

Diagnosis of congenital heart disease in the fetus should prompt assessment for extracardiac abnormalities and associated genetic abnormalities once maternal consent is obtained. Pediatric cardiologists, in conjunction with maternal-fetal medicine, neonatology, and cardiothoracic surgery subspecialists, should counsel families about the details of the congenital heart defect as well as prenatal and postnatal management.

RESULTS

Prenatal diagnosis often leads to increased maternal depression and anxiety; however, it decreases morbidity and mortality for many congenital heart defects by allowing clinicians the opportunity to optimize prenatal care and plan delivery based on the specific lesion. Changes in prenatal care can include more frequent assessments through the remainder of the pregnancy, maternal medication administration, or, in selected cases, in utero cardiac catheter intervention or surgical procedures to optimize postnatal outcomes. Delivery planning may include changing the location, timing or mode of delivery to ensure that the neonate is delivered in the most appropriate hospital setting with the required level of hospital staff for immediate postnatal stabilization.

CONCLUSIONS

Based on the specific congenital heart defect, prenatal echocardiogram assessment in late gestation can often aid in predicting the severity of postnatal instability and guide the medical or interventional level of care needed for immediate postnatal intervention to optimize the transition to postnatal circulation.

Association between maternal oxygenation and brain growth in fetuses with left-sided cardiac obstructive lesions

OBJECTIVE

Impaired brain growth has been observed in fetuses with left-sided obstructive lesions (LSOL). Maternal oxygenation (MO) can alter fetal cerebral oxygenation and vascular reactivity. Our aim was to observe whether brain growth improves during MO in fetuses with LSOL.

METHODS

Forty-six fetuses with LSOL and 23 control fetuses were enrolled in this prospective longitudinal study. Fetuses with LSOL were subgrouped into those with MO (LSOL-MO, n = 23) and those without MO (LSOL-nMO, n = 23). Fetal head circumference (HC) and total intracranial volume (TIV) were evaluated serially at 4-week intervals. Brain biometry and growth were analyzed using linear mixed models adjusted for gestational age and sex. Spearman's correlation coefficients were calculated to identify baseline characteristics predictive of brain growth in the LSOL-MO group.

RESULTS

Duration of MO therapy had significant interaction effects on cerebral biometry in fetuses with LSOL. TIV increased more rapidly after 8 weeks of oxygen exposure and HC was larger after 16 weeks of oxygen exposure in the LSOL-MO group compared with the LSOL-nMO group (P &lt; 0.001). The change in TIV at the final time- point relative to the initial timepoint in the LSOL-MO group correlated negatively with the baseline pulsatility index of the middle cerebral artery (r = -0.58, P = 0.003) and baseline myocardial performance index of the left ventricle (r = -0.68, P &lt; 0.001).

CONCLUSIONS

TIV and HC increased faster in fetuses with LSOL which had MO compared with those that did not. Lower cerebral vascular resistance and preserved left heart function at baseline may predict greater cerebral biometric growth during MO. Additional research, including larger serial studies, is needed to confirm these preliminary findings and evaluate the clinical application of MO in this population. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Hypoplastic Left Heart Syndrome: Is There a Role for Fetal Therapy?

During fetal life some cardiac defects may lead to diminished left heart growth and to the evolution of a form of hypoplastic left heart syndrome (HLHS). In fetuses with an established HLHS, severe restriction or premature closure of the atrial septum leads to left atrial hypertension and remodeling of the pulmonary vasculature, severely worsening an already poor prognosis. Fetal therapy, including invasive fetal cardiac interventions and non-invasive maternal hyperoxygenation, have been introduced to prevent a possible progression of left heart hypoplasia, improve postnatal outcome, or secure fetal survival. The aim of this review is to cover patient selection and possible hemodynamic effects of fetal cardiac procedures and maternal hyperoxygenation in fetuses with an evolving or established hypoplastic left heart syndrome.

Neuroplacentology in congenital heart disease: placental connections to neurodevelopmental outcomes

Children with congenital heart disease (CHD) are living longer due to effective medical and surgical management. However, the majority have neurodevelopmental delays or disorders. The role of the placenta in fetal brain development is unclear and is the focus of an emerging field known as neuroplacentology. In this review, we summarize neurodevelopmental outcomes in CHD and their brain imaging correlates both in utero and postnatally. We review differences in the structure and function of the placenta in pregnancies complicated by fetal CHD and introduce the concept of a placental inefficiency phenotype that occurs in severe forms of fetal CHD, characterized by a myriad of pathologies. We propose that in CHD placental dysfunction contributes to decreased fetal cerebral oxygen delivery resulting in poor brain growth, brain abnormalities, and impaired neurodevelopment. We conclude the review with key areas for future research in neuroplacentology in the fetal CHD population, including (1) differences in structure and function of the CHD placenta, (2) modifiable and nonmodifiable factors that impact the hemodynamic balance between placental and cerebral circulations, (3) interventions to improve placental function and protect brain development in utero, and (4) the role of genetic and epigenetic influences on the placenta-heart-brain connection. IMPACT: Neuroplacentology seeks to understand placental connections to fetal brain development. In fetuses with CHD, brain growth abnormalities begin in utero. Placental microstructure as well as perfusion and function are abnormal in fetal CHD.

Fetal Hemodynamic Response to Maternal Oxygenation in Normal and Complicated Pregnancies

Maternal oxygenation (MO) is widely applied in obstetrics. Scholars have conducted numerous studies on maternal hyperoxygenation and have reported many theoretical and applied achievements and a number of different points of view. The main purpose of this article is to discuss the effect of maternal oxygenation on fetal circulation during normal and complicated pregnancies and to ascertain its potential side effects and research gaps in this field. In complicated pregnancies, the fetus may benefit from oxygen therapy. However, large randomized controlled trials and longitudinal studies are necessary to support the widespread application of maternal oxygenation in this context.

Maternal hyperoxygenation in congenital heart disease

The importance of prenatal diagnosis and fetal intervention has been increasing as a preventative strategy for improving the morbidity and mortality in congenital heart disease (CHD). The advancements in medical imaging technology have greatly enhanced our understanding of disease progression, assessment, and impact in those with CHD. In particular, there has been a growing focus on improving the morbidity and mortality of fetuses diagnosed with left-sided lesions. The disruption of fetal hemodynamics resulting from poor structural developmental of the left outflow tract during cardiogenesis is considered a major factor in the progressive lethal underdevelopment of the left ventricle (LV). This positive feedback cycle of inadequate flow and underdevelopment of the LV leads to a disrupted fetal circulation, which has been described to impact fetal brain growth where systemic outflow is poor and, in some cases, the fetal lungs in the setting of a restrictive interatrial communication. For the past decade, maternal hyperoxygenation (MH) has been investigated as a diagnostic tool to assess the pulmonary vasculature and a therapeutic agent to improve the development of the heart and brain in fetuses with CHD with a focus on left-sided cardiac defects. This review discusses the findings of these studies as well as the utility of acute and chronic administration of MH in CHD.

Fetal cerebrovascular response to maternal hyperoxygenation in congenital heart disease: effect of cardiac physiology

OBJECTIVE

Fetal cerebrovascular resistance is influenced by several factors in the setting of intact autoregulation to allow for normal cerebral blood flow and oxygenation. Maternal hyperoxygenation (MH) allows for acute alterations in fetal physiology and can be a tool to test cerebrovascular reactivity in late-gestation fetuses. In this study, we utilized MH to evaluate cerebrovascular reactivity in fetuses with specific congenital heart disease (CHD).

METHODS

This was a cross-sectional study of fetuses with complex CHD compared to controls without CHD. CHD cases were grouped according to physiology into: left-sided obstructive lesion (LSOL), right-sided obstructive lesion (RSOL) or dextro-transposition of the great arteries (d-TGA). Subjects underwent MH testing during the third-trimester fetal echocardiogram. The pulsatility index (PI) was calculated for the fetal middle cerebral artery (MCA), umbilical artery (UA) and branch pulmonary artery (PA). The change in PI from baseline to during MH was compared between each CHD group and controls.

RESULTS

Sixty pregnant women were enrolled (CHD, n = 43; control, n = 17). In the CHD group, there were 27 fetuses with LSOL, seven with RSOL and nine with d-TGA. Mean gestational age was 33.9 (95% CI, 33.6-34.2) weeks. At baseline, MCA-PI Z-score was lowest in the LSOL group (-1.8 (95% CI, -2.4 to -1.2)) compared with the control group (-0.8 (95% CI, -1.3 to -0.3)) (P = 0.01). In response to MH, MCA-PI Z-score increased significantly in the control and d-TGA groups but did not change significantly in the LSOL and RSOL groups. The change in MCA-PI Z-score was significantly higher in the control group than in the LSOL group (0.9 (95% CI, 0.42-1.4) vs 0.12 (95% CI, -0.21 to 0.45); P = 0.03). This difference was more pronounced in the LSOL subgroup with retrograde aortic arch flow. Branch PA-PI decreased significantly in response to MH in all groups, with no difference in the change from baseline to MH between the groups, while UA-PI was unchanged during MH compared with at baseline.

CONCLUSIONS

The fetal cerebrovascular response to MH varies based on the underlying CHD diagnosis, suggesting that cardiovascular physiology may influence the autoregulatory capacity of the fetal brain. Further studies are needed to determine the clinical implications of these findings on long-term neurodevelopment in these at-risk children. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Fetal Cerebral Oxygenation Is Impaired in Congenital Heart Disease and Shows Variable Response to Maternal Hyperoxia

Background

Impairments in fetal oxygen delivery have been implicated in brain dysmaturation seen in congenital heart disease (CHD), suggesting a role for in utero transplacental oxygen therapy. We applied a novel imaging tool to quantify fetal cerebral oxygenation by measuring T2* decay. We compared T2* in fetuses with CHD with controls with a focus on cardiovascular physiologies (transposition or left‐sided obstruction) and described the effect of brief administration of maternal hyperoxia on T2* decay.

Methods and Results

This is a prospective study performed on pregnant mothers with a prenatal diagnosis of CHD compared with controls in the third trimester. Participants underwent a fetal brain magnetic resonance imaging scan including a T2* sequence before and after maternal hyperoxia. Comparisons were made between control and CHD fetuses including subgroup analyses by cardiac physiology. Forty‐four mothers (CHD=24, control=20) participated. Fetuses with CHD had lower total brain volume (238.2 mm³, 95% CI, 224.6–251.9) compared with controls (262.4 mm³, 95% CI, 245.0–279.8, P=0.04). T2* decay time was faster in CHD compared with controls (beta=−14.4, 95% CI, −23.3 to −5.6, P=0.002). The magnitude of change in T2* with maternal hyperoxia was higher in fetuses with transposition compared with controls (increase of 8.4 ms, 95% CI, 0.5–14.3, P=0.01), though between‐subject variability was noted.

Conclusions

Cerebral tissue oxygenation is lower in fetuses with complex CHD. There was variability in the response to maternal hyperoxia by CHD subgroup that can be tested in future larger studies. Cardiovascular physiology is critical when designing neuroprotective clinical trials in the fetus with CHD.

Prenatal prediction of neonatal haemodynamic adaptation after maternal hyperoxygenation

Abstract

The reactivity of the pulmonary vascular bed to the administration of oxygen is well established in the post-natal circulation. The vasoreactivity demonstrated by the fetal pulmonary artery Doppler waveform in response to maternal hyperoxia has been investigated. We sought to investigate the relationship between the reactivity of the fetal pulmonary arteries to hyperoxia and subsequent neonatal cardiac function in the early newborn period.

Methods

This explorative study with convenience sampling measured pulsatility index (PI), resistance index (RI), acceleration time (AT), and ejection time (ET) from the fetal distal branch pulmonary artery (PA) at baseline and following maternal hyperoxygenation (MH). Oxygen was administered for 10 min at a rate of 12 L/min via a partial non-rebreather mask. A neonatal functional echocardiogram was performed within the first 24 h of life to assess ejection fraction (EF), left ventricular output (LVO), and neonatal pulmonary artery AT (nPAAT). This study was conducted in the Rotunda Hospital, Dublin, Ireland.

Results

Forty-six women with a singleton pregnancy greater than or equal to 31 weeks’ gestational age were prospectively recruited to the study. The median gestational age was 35 weeks. There was a decrease in fetal PAPI and PARI following MH and an increase in fetal PAAT, leading to an increase in PA AT:ET. Fetuses that responded to hyperoxygenation were more likely to have a higher LVO (135 ± 25 mL/kg/min vs 111 ± 21 mL/kg/min, p < 0.01) and EF (54 ± 9% vs 47 ± 7%,p = 0.03) in the early newborn period than those that did not respond to MH prenatally. These findings were not dependent on left ventricular size or mitral valve (MV) annular diameter but were related to an increased MV inflow. There was no difference in nPAAT.

Conclusion

These findings indicate a reduction in fetal pulmonary vascular resistance (PVR) and an increase in pulmonary blood flow and left atrial return following MH. The fetal response to hyperoxia reflected an optimal adaptation to postnatal life with rapid reduction in PVR increasing measured cardiac output.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-020-03403-y.

Cerebral hemodynamic response to short-term maternal hyperoxygenation in fetuses with borderline small left hearts

BACKGROUND

Hypoxia delays brain maturation and contributes to neurodevelopmental morbidity in fetuses with congenital heart defects (CHDs). Maternal hyperoxygenation (MH) can, in theory, promote oxygen/nutrient delivery to the fetal brain, owing to an improved heart structure/function and increased fetal oxygen content. We aimed to determine whether MH alters fetal cerebral hemodynamics in fetuses with CHD.

METHODS

Twenty-eight fetuses with borderline small left hearts and 28 age-matched normal fetuses were enrolled and subdivided by gestational age (GA): 23^+ 0 ~ 27^+ 6 weeks and 28^+ 0 ~ 36^+ 6 weeks. The middle cerebral artery pulsatility index (MCA-PI), vascular index (VI), flow index (FI) and vascular/flow index (VFI) were measured with baseline room air, after 10 min of MH and after 10 min of recovery for all subjects.

RESULTS

MCA-PI, VI, FI and VFI did not differ with MH in the normal fetuses. In fetuses with borderline small left hearts, MCA-PI increased and VI, FI and VFI significantly decreased during the 3rd trimester (from 1.44 ± 0.27, 3.19 ± 0.87, 56.91 ± 9.19, and 1.30 ± 0.33 at baseline to 1.62 ± 0.15, 2.37 ± 0.37, 45.73 ± 4.59, and 0.94 ± 0.15 during MH, respectively, P < 0.05), but this response was not apparent during mid-gestation (p > 0.05). These parameters returned to the baseline levels during the recovery phase. The change in cerebral perfusion depended on the baseline MCA-PI and increased the combined cardiac index (CCOi).

CONCLUSIONS

MH alters the cerebral hemodynamics of fetuses with borderline small left hearts during the third trimester. Further investigation is needed to determine whether MH may benefit brain growth and neurodevelopment in this high-risk population.

Fetal acute cerebral vasoreactivity to maternal hyperoxia in low-risk pregnancies: a cross-sectional study

OBJECTIVE

To establish whether fetal cerebral vasoreactivity (CVR_O2 ), following maternal hyperoxia, is predicted by fetal cerebral and uteroplacental Doppler pulsatility indices (PI) at baseline, fetal pulmonary vasoreactivity to oxygen (PVR_O2 ), gestational age (GA), or sex.

METHODS

Pulsatility index of middle (MCA), anterior (ACA), posterior cerebral (PCA), umbilical (UA), uterine (UtA), and branch of the pulmonary arteries (PA) were obtained, by ultrasound, before (baseline), during (hyperoxia) and after 15 minutes of maternal administration of 8 L/min of 100% oxygen, through a non-rebreathing face mask, in normal singleton pregnancies within 20 to 38 weeks' gestation. CVR_O2 was defined as changes greater than zero in z score of PI of the cerebral arteries from baseline to hyperoxia. Logistic modeling was applied to identify CVR_O2 predictors.

RESULTS

A total of 97 pregnancies were eligible. In the overall population, median z scores of PI of MCA, ACA, and PCA did not differ between study phases. Based on the logistic model, baseline z scores for cerebral PI and GA were the best predictors of CVR_O2 .

CONCLUSIONS

In low-risk pregnancies, fetal CVR_O2 to hyperoxia does not occur uniformly but depends on cerebral PI and GA at baseline. These findings may provide useful reference points when oxygen is administered in high-risk pregnancies.

Maternal hyperoxygenation for the human fetus: should studies be curtailed?

Congenital hypoplasia of left heart structures in fetuses frequently progresses with gestational development. Interference with cerebral development is common in these fetuses. Chronic maternal hyperoxygenation (MHO) has been recommended to increase left ventricular size and to limit cerebral damage. The effects of MHO on cerebral blood flow and metabolism have been studied in normal fetuses and fetuses with left heart hypoplasia. Maternal hyperoxygenation increases fetal pulmonary blood flow. This is associated with reduction of foramen ovale flow, thus limiting the increase in left ventricular output. Modest increase in the size of left heart structures has been reported, but in another study, no significant improvement occurred. In sheep fetuses increased oxygenation results in marked reduction of cerebral blood flow, with no change in oxygen delivery or consumption by the brain, but significant reduction in cerebral glucose delivery and consumption. In one study of fetuses with left heart hypoplasia, chronic MHO was associated with decrease in head size. The effectiveness of MHO in improving left ventricular development is controversial. MHO is, however, associated with reduction of cerebral blood flow and possible interference with cerebral development. In view of this it is recommended that all studies of chronic maternal hyperoxygenation be curtailed.

New Aspects in the Diagnosis and Therapy of Fetal Hypoplastic Left Heart Syndrome

Fetal hypoplastic left heart syndrome (HLHS) is a severe congenital heart disease with a lethal prognosis without postnatal therapeutic intervention or surgery. The aim of this article is to give a brief overview of new findings in the field of prenatal diagnosis and the therapy of HLHS. As cardiac output in HLHS children depends on the right ventricle (RV), prenatal assessment of fetal RV function is of interest to predict poor functional RV status before the RV becomes the systemic ventricle. Prenatal cardiac interventions such as fetal aortic valvuloplasty and non-invasive procedures such as maternal hyperoxygenation seem to be promising treatment options but will need to be evaluated with regard to long-term outcomes. Novel approaches such as stem cell therapy or neuroprotection provide important clues about the complexity of the disease. New aspects in diagnostics and therapy of HLHS show the potential of a targeted prenatal treatment planning. This could be used to optimize parental counseling as well as pre- and postnatal management of affected children.