A few months ago I was somewhat surprised to see a news story about scientists who had managed to get the natural balance just right to be able to support the growth of lamb foetuses in plastic bags (“BioBags”). This was not like anything I expected to see in this half of the century, and sounded like something from a science fiction movie, so you can understand my excitement at this achievement. In this blog post I will aim to explain the challenges the scientists faced in trying to get this system to support life and what this could mean in the future, not only for animals but for humans too.
The most obvious challenge when designing the Biobag was what to grow the foetus in. Amniotic fluid for a foetus is not only a cushion, protecting it from knocks and bumps, but it aids in bone and limb growth, and supplies the foetus with vital nutrients. Some also say that swallowing amniotic fluid helps to foster antimicrobial protection and to develop the foetus’ gastrointestinal system. Therefore, it is crucial to get the volume and composition of artificial amniotic fluid right. Complicating this is the fact that these conditions change throughout gestation to match the foetus’ stage of growth and needs.
The synthetic amniotic fluid used in the Biobags is a neutral electrolyte solution composed of hydrogen carbonate, sodium, chloride, potassium and calcium salts. These are all nutrients which the foetus needs to grow and develop. Although the initial experiments just used this simple electrolyte solution, the scientists’ future research will focus on improving and optimising the solution to be used in the Biobags .
Another challenge was how to get oxygen and nutrients to the foetus and remove any waste produced. Placental transfer is vital for the gas exchange and excretion of waste for the foetus. By inserting cannulas into the major veins and arteries in the lamb’s umbilical cord, these blood vessels can be attached to a filtering and exchange system for gases to be transferred to and from the lamb’s body. This, however is not done by a man-made pump, but instead by the natural pump that exists in all mammals’ bodies; the heart. Using the foetal heart to drive the circulation instead of an artificial pump has many advantages, including a natural regulation of blood pressure, and simplicity – this is also closer to the natural situation. The heart of the foetus is able to pump the blood through the external gas exchange system at the perfect pressure to maintain the correct blood gas content but not too high that the blood vessels of the umbilical cord or the umbilical cord to machine interface are under threat of rupture.
However, the volume of the oxygenator is crucial. If too high or low a volume, then the foetus will become haemodynamically unstable (an instability in the flow of blood around the body) and the system will not be able to deliver sufficient oxygen to the foetus.
Infection can be lethal to any foetus, even those cushioned safely inside a maternal uterus. However, this is a major consideration for foetuses in Biobags. The scientists lost many foetuses in their research because of sepsis (an infection), but have significantly reduced losses by having a ‘closed’ system with microbial filters and sterile access ports fitted for any addition of fluid or suction of meconium (faecal waste produced by the foetus).
Biobags have successfully grown infant lambs from a stage that would be equivalent to extremely premature human infants for up to 4 weeks. This may not sound like a long time, but this extra developmental time can be the difference between life and death or normal brain/lung function and life changing damage to human infants. It is also important to note that this 4 week period was not due to mechanical failure or a mishap in the system, the experiment had to be terminated at this time because of animal protocol limitations. The foetuses could be sustained in Biobags for much longer.
The scientists hope that Biobags could be used in the future to help human infants of just 23-25 weeks’ gestation to have better outcomes, and to help treat conditions such as growth retardation caused by placental insufficiency. The trials for this could occur as soon as 3 years’ time. Although there may be some psychological barriers to overcome for parents seeing their baby ‘in a bag’, the possible applications of this breakthrough technology are potentially limitless, and truly in the realms of science fiction.
 BIOLOGY DICTIONARY. (2017) Amniotic Fluid. [Online] Available from: https://biologydictionary.net/amniotic-fluid/ [Accessed: 15th September 2017]
 SANGILD, P. T. et al. (2003) Ingestion of Amniotic Fluid Before Birth: Does It Improve Intestinal Function? [Online] Available from: https://actavetscand.biomedcentral.com/articles/10.1186/1751-0147-44-S1-P109 [Accessed: 15th September 2017]
 PARTRIDGE, E. A. et al. (2017) An Extra-uterine System To Physiologically Support The Extreme Premature Lamb. [Online] Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5414058/ [Accessed: 17th September 2017]
 CHEGG. (2017) Signs And Symptoms Of Hemodynamic Instability. [Online] Available from: http://www.chegg.com/homework-help/definitions/signs-and-symptoms-of-hemodynamic-instability-14 [Accessed: 17th September 2017]
 TAYAG, Y. (2017) How a Plastic Bag Became a Womb for Premature Lambs. [Online] Available from: https://www.inverse.com/article/30836-premature-lamb-artificial-womb-uterus-plastic-bag [Accessed: 17th September 2017]