New Womb-Like Device May Transform Care for Extremely Premature Infants
A unique womb-like environment designed by pediatric researchers at Children’s Hospital of Philadelphia — which is in an experimental stage using animal models — could transform care for extremely premature babies: after birth, they would be immersed in lab-made amniotic fluid — and kept underwater for weeks.
Most previous attempts at creating a womb-like device used artificial pumps to drive the blood through the system, causing heart failure. In the system invented by Partridge et al , the fetal heart is the only pump. It is different in other key ways. Use of the bag, rather than a more open container, nearly eliminated the infection issues that contributed to previous failures. And while previous attempts relied on blood vessels in the neck, the authors figured out how to quickly and successfully insert tubes (cannulas) into the notoriously touchy umbilical vessels. Image credit: Children’s Hospital of Philadelphia.
In the United States, 30,000 babies are born every year at 26 weeks gestation or less.
This extreme prematurity is the nation’s leading cause of infant mortality and morbidity. Fewer than half survive. Of those who do, 90% suffer sickness and disability, such as lung disease, cerebral palsy, blindness and brain damage.
Surgeons and neonatologists witness the effects of prematurity every day. And now a research team at Children’s Hospital of Philadelphia has innovated a system that could revolutionize care for these tiny and vulnerable babies.
The team — led by Dr. Alan W. Flake, a fetal surgeon and director of the Center for Fetal Research in the Center for Fetal Diagnosis and Treatment at Children’s Hospital of Philadelphia — reports on preclinical studies of their extra-uterine support device in the journal Nature Communications .
“Our system could prevent the severe morbidity suffered by extremely premature infants by potentially offering a medical technology that does not currently exist,” Dr. Flake said.
“These infants have an urgent need for a bridge between the mother’s womb and the outside world. If we can develop an extra-uterine system to support growth and organ maturation for only a few weeks, we can dramatically improve outcomes for extremely premature babies.”
In the current study, Dr. Flake and co-authors describe the evolution of their system over three years, through a series of four prototypes, beginning with a glass incubator tank, and progressing to the current device.
The eight preterm lambs tested in the most recent prototype were physiologically equivalent to a 23- or 24-week-gestation human infant.
The current system mimics life in the uterus as closely as possible, building on knowledge from previous neonatal research.
There is no external pump to drive circulation, because even gentle artificial pressure can fatally overload an underdeveloped heart, and there is no ventilator, because the immature lungs are not yet ready to do their work of breathing in atmospheric oxygen.
Instead, the baby’s heart pumps blood via the umbilical cord into the system’s low-resistance external oxygenator that substitutes for the mother’s placenta in exchanging oxygen and carbon dioxide.
In addition, amniotic fluid, produced in the laboratory, flows into and out of the bag.
“Fetal lungs are designed to function in fluid, and we simulate that environment here, allowing the lungs and other organs to develop, while supplying nutrients and growth factors,” said co-author Dr. Marcus G. Davey.
The sealed, sterile environment inside the system is insulated from variations in temperature, pressure and light, and particularly from hazardous infections.
Previously, researchers have investigated versions of an artificial placenta in animal models, but pumpless systems have achieved a maximum duration of 60 hours, and the animals have sustained brain damage.
The new system, in contrast, has operated up to 670 hours (28 days) with some animals, which remained healthy. The lambs showed normal breathing and swallowing, opened their eyes, grew wool, became more active, and had normal growth, neurological function and organ maturation.
“We don’t aim to extend viability to an earlier period than the current mark of 23 weeks. Before that point, limitations of physical size and physiologic functioning would impose unacceptably high risks,” Dr. Flake said.
“This system is potentially far superior to what hospitals can currently do for a 23-week-old baby born at the cusp of viability. This could establish a new standard of care for this subset of extremely premature infants.”