Achieving sustained extrauterine life: Challenges of an artificial placenta in fetal pigs as a model of the preterm human fetus

Artificial womb technology - A more physiologic solution to treating extreme prematurity

Treatment of extreme premature infants (EPI) is limited by developmental immaturity primarily of the lung. A paradigm shift towards a more physiologic treatment of EPI as fetal neonates or fetonates, by keeping them in a womb-like environment to allow continued organ maturation, is the rationale for artificial womb technology. In this review, we discuss the artificial placenta and womb technology, it's rationale, the history of its development, the most recent preclinical models described in the literature and finally pertinent ethical considerations.

Value sensitive design and the artificial placenta

Artificial placenta technologies (also termed 'artificial wombs') for use in place of conventional neonatal intensive care are increasingly closer to first-in-human use. There is growing ethical interest in partial ectogestation (the use of an artificial placenta to continue gestation of an underdeveloped human entity extra uterum), however, there has been little reflection on the ethical issues in the design of the technology. While some have noted the importance of such reflection, and others have noted that a 'value sensitive design' approach should be preferred, they have not elaborated on what this means. In this article, we consider what a value sensitive design approach to artificial placenta design might encompass. We believe that applying this framework to the topic at hand raises theoretical and substantive ethical questions that merit further elucidation. Highlighting that there is a careful need to separate preferences from values and that our intervention should be considered only a starting point, we explore some of the values that could be used to make ethical design choices about the artificial placenta: efficacy, compassion and accessibility.

Echocardiographic assessment of cardiovascular physiology of preterm miniature piglets supported with a pumped artificial placenta system

OBJECTIVES

We evaluated fetal cardiovascular physiology and mode of cardiac failure in premature miniature piglets on a pumped artificial placenta (AP) circuit.

METHODS

Fetal pigs were cannulated via the umbilical vessels and transitioned to an AP circuit composed of a centrifugal pump and neonatal oxygenator and maintained in a fluid-filled biobag. Echocardiographic studies were conducted to measure ventricular function, umbilical blood flow, and fluid status. In utero scans were used as control data.

RESULTS

AP fetuses (n = 13; 102±4d gestational age [term 115d]; 616 ± 139 g [g]; survival 46.4 ± 46.8 h) were tachycardic and hypertensive with initially supraphysiologic circuit flows. Increased myocardial wall thickness was observed. Signs of fetal hydrops were present in all piglets. Global longitudinal strain (GLS) measurements increased in the left ventricle (LV) after transition to the circuit. Right ventricle (RV) and LV strain rate decreased early during AP support compared with in utero measurements but recovered toward the end of the experiment. Fetuses supported for >24 h had similar RV GLS to in utero controls and significantly higher GLS compared to piglets surviving only up to 24 h.

CONCLUSIONS

Fetuses on a pump-supported AP circuit experienced an increase in afterload, and redistribution of blood flow between the AP and systemic circulations, associated with elevated end-diastolic filling pressures. This resulted in heart failure and hydrops. These preterm fetuses were unable to tolerate the hemodynamic changes associated with connection to the current AP circuit. To better mimic the physiology of the native placenta and preserve normal fetal cardiovascular physiology, further optimization of the circuit will be required.

Artificial placentas, pregnancy loss and loss-sensitive care

In this paper, we explore how the prospect of artificial placenta technology (nearing clinical trials in human subjects) should encourage further consideration of the loss experienced by individuals when their pregnancy ends unexpectedly. Discussions of pregnancy loss are intertwined with procreative loss, whereby the gestated entity has died when the pregnancy ends. However, we demonstrate how pregnancy loss can and does exist separate to procreative loss in circumstances where the gestated entity survives the premature ending of the pregnancy. In outlining the value that can be attached to pregnancy beyond fetal-centric narratives, we illustrate how pregnancy loss, separate to procreative loss, can be experienced. This loss has already been recognised among parents who have experienced an unexpected early ending of their pregnancy, resulting in their child being cared for in neonatal intensive care unit. Artificial placentas, however, may exacerbate these feelings and make pregnancy loss (without procreative loss) more visible. We argue that pregnancy is an embodied state in which gestation is facilitated by the body but gestation itself should be recognised as a process-and one that could be separable from pregnancy. In demarcating the two, we explore the different ways in which pregnancy loss can be understood. Our objective in this paper goes beyond contributing to our philosophical understanding of pregnancy towards practical-orientated conclusions regarding the care pathways surrounding the artificial placenta. We make recommendations including the need for counselling and careful consideration of the language used when an artificial placenta is used.

Transferring an extremely premature infant to an extra-uterine life support system: a prospective view on the obstetric procedure

To improve care for extremely premature infants, the development of an extrauterine environment for newborn development is being researched, known as Artificial Placenta and Artificial Womb (APAW) technology. APAW facilitates extended development in a liquid-filled incubator with oxygen and nutrient supply through an oxygenator connected to the umbilical vessels. This setup is intended to provide the optimal environment for further development, allowing further lung maturation by delaying gas exposure to oxygen. This innovative treatment necessitates interventions in obstetric procedures to transfer an infant from the native to an artificial womb, while preventing fetal-to-neonatal transition. In this narrative review we analyze relevant fetal physiology literature, provide an overview of insights from APAW studies, and identify considerations for the obstetric procedure from the native uterus to an APAW system. Lastly, this review provides suggestions to improve sterility, fetal and maternal well-being, and the prevention of neonatal transition.

The alterations of cardiac function during venovenous artificial placenta support in fetal goats

INTRODUCTION

Venovenous artificial placenta (VVAP) may mimic the intrauterine environment for maintaining fetal circulation. However, changes in ventricular function in fetal goats undergoing VVAP support remain unclear.

METHODS

Pump-assisted VVAPs were established in five fetal goats for 9 h. The myocardial performance index (Tei index), cardiac output (CO), and blood biochemical parameters were measured during VVAP support.

RESULTS

An increasing trend of the right ventricular (RV) Tei index was seen during VVAP support (p for trend < 0.01). The right ventricular cardiac output (RVCO) increased after the initiation of VVAP, while a significant trend of reduction was observed after 3 h (p for trend = 0.03). During VVAP support, we observed remarkable elevations of plasma cTnI and arterial lactic acid, which were positively correlated with the RV Tei index, but not the left ventricular (LV) Tei index, LVCO, and RVCO.

CONCLUSIONS

The RVCO increases initially while a tendency of decrease could be observed during VVAP support. Special attention should be paid to right ventricular dysfunction during VVAP support.

Clinical aspects of umbilical cord cannulation during transfer from the uterus to a liquid-based perinatal life support system for extremely premature infants a qualitative generic study

A liquid-based perinatal life support system (PLS) for extremely premature infants (born before 28 week of gestational age) envisions a connection between the infant's native umbilical cord and an artificial placenta system through cannulation. This system mimics a natural mothers' womb to achieve better organ maturations. The objective of this study is to gain insight into the clinical focus points of umbilical cord cannulation and how cannulation should be addressed in extremely premature infants during the transfer from the uterus to an in-utero simulating liquid-based PLS system. We performed an explorative qualitative study. Twelve medical specialists with knowledge of vessel cannulation participated. We collected data through twelve interviews and two focus group discussions. Data were analyzed using inductive content and constant comparison analysis via open and axial coding. Results were derived on the following topics: (1) cannulation technique, (2) cannula fixation, (3) local and systemic anticoagulation, and (4) vasospasm. A side-entry technique is preferred as this may decrease wall damage, stabilizes the vessel better and ensures continuous blood flow. Sutures, especially via an automatic microsurgery instrument, are favored above glue, stents, or balloons as these may be firmer and faster. Medication possibilities for both vasospasm and anticoagulation should function locally since there were uncertainties regarding the systemic effects. According to the findings of this research, the needed umbilical cord cannulation method should include minimal wall damage, improved vascular stability, blood flow maintenance, a strong fixation connection, and local anticoagulation effect.

Ethical challenges in first-in-human trials of the artificial placenta and artificial womb: not all technologies are created equally, ethically

Artificial placenta and artificial womb technologies to support extremely premature neonates are advancing toward clinical testing in humans. Currently, no recommendations exist comparing these approaches to guide study design and optimal enrollment eligibility adhering to principles of research ethics. In this paper, we will explore how scientific differences between the artificial placenta and artificial womb approaches create unique ethical challenges to designing first-in-human trials of safety and provide recommendations to guide ethical study design for initial human translation.

Artificial placenta support of extremely preterm ovine fetuses at the border of viability for up to 336 hours with maintenance of systemic circulation but reduced somatic and organ growth

Introduction: Artificial placenta therapy (APT) is an experimental life support system to improve outcomes for extremely preterm infants (EPI) less than 1,000 g by obviating the need for pulmonary gas exchange. There are presently no long-term survival data for EPI supported with APT. To address this, we aimed to maintain 95d-GA (GA; term-150d) sheep fetuses for up to 2 weeks using our APT system. Methods: Pregnant ewes (n = 6) carrying singleton fetuses underwent surgical delivery at 95d GA. Fetuses were adapted to APT and maintained for up to 2 weeks with constant monitoring of key physiological parameters and extensive time-course blood and urine sampling, and ultrasound assessments. Six age-matched in-utero fetuses served as controls. Data were tested for group differences with ANOVA. Results: Six APT Group fetuses (100%) were adapted to APT successfully. The mean BW at the initiation of APT was 656 ± 42 g. Mean survival was 250 ± 72 h (Max 336 h) with systemic circulation and key physiological parameters maintained mostly within normal ranges. APT fetuses had active movements and urine output constantly exceeded infusion volume over the experiment. At delivery, there were no differences in BW (with edema in three APT group animals), brain weight, or femur length between APT and in-utero Control animals. Organ weights and humerus lengths were significantly reduced in the APT group (p < 0.05). Albumin, IGF-1, and phosphorus were significantly decreased in the APT group (p < 0.05). No cases of positive blood culture were detected. Conclusion: We report the longest use of APT to maintain extremely preterm fetuses to date. Fetal systemic circulation was maintained without infection, but growth was abnormal. This achievement suggests a need to focus not only on cardiovascular stability and health but also on the optimization of fetal growth and organ development. This new challenge will need to be overcome prior to the clinical translation of this technology.

Acute fetal cardiovascular adaptation to artificial placenta in sheep model

OBJECTIVE

To describe the acute cardiovascular adaptation of the fetus after connection to an artificial placenta (AP) in a sheep model, using ultrasound and invasive and non-invasive hemodynamic assessment.

METHODS

This was an experimental study of 12 fetal sheep that were transferred to an AP system, consisting of a pumpless circuit with umbilical cord connection, at 109-117 days' gestation. The study was designed to collect in-utero and postcannulation measurements in all the animals. The first six consecutive fetuses were fitted with intravascular catheters and perivascular probes to obtain invasive physiological data, including arterial and venous intravascular pressures and perivascular blood flows, with measurements taken in utero and at 5 and 30 min after cannulation. These experiments were designed with a survival goal of 1-3 h. The second set of six fetuses were not fitted with catheters, and experiments were aimed at 3-24 h of survival. Echocardiographic assessment of cardiac anatomy and function, as well as measurements of blood flow and pre- and postmembrane pressures recorded by circuit sensors in the AP system, were available for most of the fetuses. These data were acquired in utero and at 30 and 180 min after cannulation.

RESULTS

Compared with in-utero conditions, the pulsatility index at 30 and 180 min after connection to the AP system was reduced in the umbilical artery (median, 1.36 (interquartile range (IQR), 1.06-1.50) vs 0.38 (IQR, 0.31-0.50) vs 0.36 (IQR, 0.29-0.41); P < 0.001 for extreme timepoints) and the ductus venosus (median, 0.50 (IQR, 0.41-0.67) vs 0.29 (IQR, 0.22-0.33) vs 0.36 (IQR, 0.22-0.41); P = 0.011 for extreme timepoints), whereas umbilical venous peak velocity increased (median, 20 cm/s (IQR, 18-22 cm/s) vs 39 cm/s (IQR, 31-43 cm/s) vs 43 cm/s (IQR, 34-54 cm/s); P < 0.001 for extreme timepoints) and flow became more pulsatile. Intravascular monitoring showed that arterial and venous pressures increased transiently after connection, with median values for mean arterial pressure at baseline, 5 min and 30 min of 43 mmHg (IQR, 35-54 mmHg), 72 mmHg (IQR, 61-77 mmHg) and 58 mmHg (IQR, 50-64 mmHg), respectively (P = 0.02 for baseline vs 5 min). Echocardiography showed a similar transient elevation of fetal heart rate at 30 and 180 min after connection compared with in utero (median, 145 bpm (IQR, 142-156 bpm) vs 188 bpm (IQR, 171-209 bpm) vs 175 bpm (IQR, 165-190 bpm); P = 0.001 for extreme timepoints). Fetal cardiac structure and function were mainly preserved; median values for right fractional area change were 36% (IQR, 34-41%) in utero, 38% (IQR, 30-40%) at 30 min and 37% (IQR, 33-40%) at 180 min (P = 0.807 for extreme timepoints).

CONCLUSIONS

Connection to an AP system resulted in a transient fetal hemodynamic response that tended to normalize over hours. In this short-term evaluation, cardiac structure and function were preserved. However, the system resulted in non-physiologically elevated venous pressure and pulsatile flow, which should be corrected to avoid later impairment of cardiac function. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Advanced imaging of fetal cardiac function

Over recent decades, a variety of advanced imaging techniques for assessing cardiovascular physiology and cardiac function in adults and children have been applied in the fetus. In many cases, technical development has been required to allow feasibility in the fetus, while an appreciation of the unique physiology of the fetal circulation is required for proper interpretation of the findings. This review will focus on recent advances in fetal echocardiography and cardiovascular magnetic resonance (CMR), providing examples of their application in research and clinical settings. We will also consider future directions for these technologies, including their ongoing technical development and potential clinical value.

Report of an Experiment With a Fetal Ex-Utero Support System in Piglets

Extreme prematurity remains one of the leading causes of neonatal death. An ex-utero treatment strategy that allows the fetus to develop beyond this period until capable of tolerating the transition to post-natal physiology would significantly impact the quality of care offered for this pre-viable patient population. In this study, we report our experience with an ex-utero support system for fetal pigs with the goal of support and survival for eight hours. Our experiment included two pigs at a gestational age equivalent to a 32-week human fetus. Following ultrasound assessment and delivery via hysterotomy, the fetuses were transferred to a 40 L glass aquarium filled with warmed lactated Ringer's solution and connected to an arteriovenous (AV) circuit that included a centrifugal pump and a pediatric oxygenator. Fetus 1 was successfully cannulated and survived for seven hours (expected maximum duration of eight hours). Fetus 2 died shortly after hysterotomy, secondary to failure at the cannulation stage. Our results suggest that ex-utero support of the premature fetal pig is feasible, contributing to a scarce body of evidence. However, further studies are needed before effectively translating an artificial placenta system into the clinical arena.

Design and In Vitro Evaluation of an Artificial Placenta Made From Hollow Fiber Membranes

For infants born at the border of viability, care practices and morbimortality rates vary widely between centers. Trends show significant improvement, however, with increasing gestational age and weight. For periviable infants, the goal of critical care is to bridge patients to improved outcomes. Current practice involves ventilator therapy, resulting in chronic lung injuries. Research has turned to artificial uterine environments, where infants are submerged in an artificial amniotic fluid bath and provided respiratory assistance via an artificial placenta. We have developed the Preemie-Ox, a hollow fiber membrane bundle that provides pumpless respiratory support via umbilical cord cannulation. Computational fluid dynamics was used to design an oxygenator that could achieve a carbon dioxide removal rate of 12.2 ml/min, an outlet hemoglobin saturation of 100%, and a resistance of less than 71 mmHg/L/min at a blood flow rate of 165 ml/min. A prototype was utilized to evaluate in-vitro gas exchange, resistance, and plasma-free hemoglobin generation. In-vitro gas exchange was 4% higher than predicted results and no quantifiable plasma-free hemoglobin was produced.

Facts and doubts on the beginning of human life - scientific, legal, philosophical and religious controversies

It is very complicated to give correct answer to the question "How to define human life?" Nowadays dilemmas consider the respect of human life from the birth to death involve not just biology but also other sciences like philosophy, theology, sociology, psychology, law and politics. These sciences evaluate the topic from different points of view. Integration of all of these perspectives could result with a proper definition. The principal purpose of this paper is to try to determine when a human individual begins. If this proves to be too difficult, we might have to settle for a specific stage in the reproductive process before which it would be impossible to say with any plausibility that a human individual exists. It is necessary to return the moral dimension of observation to the science of life. The point is to reconcile the universal ethical principles concerning the absolute value of life with the everyday challenges and dilemmas. It is our deepest conviction that life has an absolute value and that there always remains something indestructible and substantial in life, which may neither be evaluated by anything final, nor completely reduced to the material biological equivalent and the genetic substratum.

Ethical, Translational, and Legal Issues Surrounding the Novel Adoption of Ectogestative Technologies

Increasing numbers of research teams are investigating the feasibility of developing artificial amnion and placenta technology (AAPT), commonly referred to as "artificial womb technology". This technology, aimed at supporting ex vivo gestation, has not yet been tested in humans, but it has been stated that we are closer to clinical application than ever before as breakthroughs in animal studies demonstrate good proof of principle. With these proof-of-concept models, further dissemination of AAPT as a research modality is expected. In this review article, we consider the ethical implications of the most imminent anticipated applications for AAPT. We focus specifically on the specific ethical complications regarding the improvements this technology may offer to conventional neonatal intensive care, its potential utility in facilitating prenatal interventions, and some of the broader socio-legal implications such as the debates about abortion access and reproductive and gestational choices. We discuss translational and societal questions when it comes to designing and developing this technology, like commitments to value-sensitive design, along with an examination of the legal and moral status of the entity gestating ex utero, which will be relevant for how it ought to be treated in the context of these various applications. From these perspectives, this review identifies the ethical questions that we believe to be most pressing in the development and potential introduction of AAPT, with due attention to their manifestation as translational and legal issues.

Impact of the Addition of a Centrifugal Pump in a Preterm Miniature Pig Model of the Artificial Placenta

The recent demonstration of normal development of preterm sheep in an artificial extrauterine environment has renewed interest in artificial placenta (AP) systems as a potential treatment strategy for extremely preterm human infants. However, the feasibility of translating this technology to the human preterm infant remains unknown. Here we report the support of 13 preterm fetal pigs delivered at 102 ± 4 days (d) gestation, weighing 616 ± 139 g with a circuit consisting of an oxygenator and a centrifugal pump, comparing these results with our previously reported pumpless circuit (n = 12; 98 ± 4 days; 743 ± 350 g). The umbilical vessels were cannulated, and fetuses were supported for 46.4 ± 46.8 h using the pumped AP versus 11 ± 13 h on the pumpless AP circuit. Upon initiation of AP support on the pumped system, we observed supraphysiologic circuit flows, tachycardia, and hypertension, while animals maintained on a pumpless AP circuit exhibited subphysiologic flows. On the pumped AP circuit, there was a progressive decline in umbilical vein (UV) flow and oxygen delivery. We conclude that the addition of a centrifugal pump to the AP circuit improves survival of preterm pigs by augmenting UV flow through the reduction of right ventricular afterload. However, we continued to observe the development of heart failure within a matter of days.