An artificial womb called BioBag has been demonstrated successfully with animals for the first time, an advance that could one day solve complications that critically premature human babies face outside the womb.
The lambs were the human equivalent of 23 weeks of gestation, appearing to develop normally inside a plastic bag filled with artificial amniotic fluid, the protective fluid which cushions a growing fetus. Within minutes of premature birth, scientists sealed each lamb in the BioBag, which links to a gas exchanger by their umbilical cord, replenishing their blood oxygen and infusing nutrients. The lambs breathed and swallowed the artificial amniotic fluid, which contained nutrients and chemicals which stimulated fetal growth.
HOW THEY DID IT AND WHY IT’S SIGNIFICANT
Over four weeks, scientists observed the lambs’ lungs and brains growing. They also sprouted wool, opened their eyes, wiggled, and learned to swallow, according to the study, published in Nature Communications. At the end of four weeks, the researchers switched the lambs onto a regular ventilator similar to those used by premature babies in neonatal intensive care units (NICU). They observed that the lambs’ health appeared nearly as good as a lamb the same age that had just been delivered by cesarean section. Afterward, all but one, which had developed enough to breathe on its own, were euthanized due to “animal protocol limitations rather than any instability,” and scientists examined their organs. Their lungs and brains appeared uninjured, as developed as they should be in a lamb that grew in a mother.
“This is real tomorrow’s world stuff,” says Neil Marlow, a professor of neonatal medicine at University College London. “They appear to have got lambs through four weeks which is a pretty momentous achievement.”
Extremely premature infants have “well documented, dismal outcomes,” notes Dr. Alan Flake, a fetal surgeon at the Children’s Hospital of Philadelphia (CHOP) and the study’s lead author. “If we can support growth and organ maturation for only a few weeks, we can dramatically improve outcomes for extremely premature babies,” he said.
Prematurity is the leading cause of death for newborns in the United States––and about 10 percent of babies born in the U.S. are born prematurely (born before they reach 37 weeks of pregnancy). Fully 6 percent, about 30,000 of these births, are considered critically premature (born before they reach 28 weeks of pregnancy). These infants require intensive care as they continue to develop outside their mothers’ wombs. Those who survive delivery require mechanical ventilation, medications, and nutrients and fluids provided intravenously. Even so, many of those who make it outside intensive care (between 20 and 50 percent) still suffer from health conditions that arise from their stunted development.
According to neonatologist Elizabeth Rogers, co-director of the Intensive Care Nursery Follow-Up Program of UCSF Benioff Children’s Hospital, who was not involved in the study, parents “have to make critical decisions about whether to use aggressive measures to keep these babies alive, or whether to allow for less painful, comfort care.” These decisions have a steep cost. “One of the unspoken things in extreme preterm birth is that there are families who say, ‘If I had known the outcome for my baby could be this bad, I wouldn’t have chosen to put her through everything,” she says.
Scientists have for decades attempted to develop an artificial womb that would emulate a more natural environment for premature babies to develop in.
One of the primary challenges was figuring out how to recreate the intricate circulatory system which connects a mother to her fetus. The mother’s blood flows to the baby and back, exchanging oxygen for carbon dioxide. The blood must flow with enough pressure, but artificial pumps run the risk of damaging the baby’s heart.
Dr. Flake and his colleagues solved the problem, developing a pumpless circulatory system that connected the fetus’s umbilical blood vessels to a new kind of oxygenator, moving blood smoothly through the system. Their creation was a success; the baby’s heartbeat was sufficient to power blood flow without another pump. They also found a way to reduce the risk of infection, which premature infants in open incubators face in NICUs. The artificial amniotic fluid flows in and out of BioBag just like it would in a uterus, removing waste and shielding the infant from infection.