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Operating on a baby while still inside the womb once seemed impossible, however, medical technology has advanced to the point that not only is this possible, but fetal surgery has better results than if the procedure is performed after delivery.
Fetal surgery can improve the long-term prognosis for children identified with specific birth defects, and seems particularly applicable when there are multiple pregnancies – identical twins or triplets for example. Such conditions can worsen as the fetus(es) develop, so surgeons are increasingly treating the conditions before birth.
Life-Saving Lasers for Unborn Babies
A recent TV series – Baby Surgeons: Delivering Miracles – highlighted the use of lasers for saving lives even before babies are born. It followed several families and the pioneering surgeons performing minimally invasive operations on fetuses in the womb.
During a routine 19-week scan, one fetus was identified as having congenital cystic adenomatoid malformation of the lung – a life-threatening type of cancer within the air sacs - that was stopping the lungs from developing properly. The family was offered revolutionary surgery at St George’s Hospital in London, where surgeons perform hundreds of delicate operations on unborn babies measuring only a few centimeters long.
The surgery involved using a needle and a laser to block off the blood vessel feeding the tumor; the blood vessel was no thicker than a matchstick, meaning there was no margin for error. The operation was a success and the fetus grew to full term; the little girl is, at the time of writing, around seven months old.
Twin-Twin Transfusion Syndrome and Fetoscopic Laser Surgery
Multiple pregnancies can be affected by diseases such as twin-twin transfusion syndrome (TTTS), a complication of identical twins who share one placenta. Blood flow between the twins is unequal and preferential to one of the twins, and if left untreated could lead to both twins dying before birth.
Treatment depends on the stage of pregnancy and the severity of the condition, but expectant mothers are typically offered fetal laser ablation. In this procedure, first proposed in the 1990s, a fetoscope or small camera is used to locate the abnormal blood vessel connection on the placenta between the babies and then sealed using laser energy. This prevents the abnormal exchange of fluid and can stop or reverse the disease.
Surgeons typically use a neodymium: yttrium–aluminum–garnet (Nd:YAG) laser or diode (semi‐conductor) lasers. Nd:YAG lasers typically function at a 1064 nm wavelength, and the diode laser a 940 nm wavelength and a power setting between 20 and 80 W. Both systems endlessly emit laser energy with similar absorption properties, but the Nd:YAG laser typically achieves greater optical penetration than the diode laser.
At one point, laser ablation was an unselective process; all blood vessels were coagulated across the dividing membrane, a method that carried a higher risk of fetal death. As lasers have become more precise, coagulations methods have advanced, and surgeons are now able to sequentially and selectively coagulate the blood vessels that need to be sealed.
Another recent advancement includes the ‘Solomon technique’, which coagulates the entire vascular equator from one placenta margin to the other, before moving from one edge of the placenta to the other. This reduces residual connections, ensuring diseases such as TTTS and twin anemia–polycythemia sequence (TAPS) – which causes anemia and polycythemia in the donor and recipient twin respectively - cannot reoccur.
The laser firing angle is believed to be key to successful coagulation; the more perpendicular the laser fiber is pointed at the vessel, the quicker coagulation occurs. Therefore, choosing the optimal introduction site for the fetoscope is considered one of the most important steps in the procedure.
The Future of Lasers in Medical Applications
Revolutionary surgery using the power of lasers allows fetus defects to be corrected before a child is born, with better outcomes than if the surgery was performed shortly after birth.
Advances in fetoscopic laser surgery have significantly improved over the past 25 years, with up to 70% overall double survival and approaching 80% single survival rates for TTTS. The introduction of flexible mini telescopes means the technique can be further improved, allowing for better visualization of the vascular equator, particularly in anterior placentas.
Although widely used to treat TTTS, the technique is increasingly being applied to treat other rare complications, including amniotic bands (caused by issues with blood flow), chorioangiomas (tumor of the placenta), sacrococcygeal teratomas (tumors at the base of the spine), lower urinary tract obstructions, and chest masses. There is no telling where it could be used next, and how many more fetuses it could save.
References and Further Reading
Mathis, J. et al (2015) Fetal laser therapy: applications in the management of fetal pathologies – Prenatal Diagnosis: https://obgyn.onlinelibrary.wiley.com/doi/full/10.1002/pd.4587. Accessed 26th May 2021.
Mayo Clinic, Fetal Surgery – Mayo Clinic: https://www.mayoclinic.org/tests-procedures/fetal-surgery/about/pac-20384571. Accessed 26th May 2021.
Knight, K (2021) Tiny miracles saved by surgery in the womb: Becky’s baby’s lungs were unable to form properly due to rare cancer - but operation with a needle and laser let the child live – The Daily Mail: https://www.dailymail.co.uk/health/article-9513681/Tiny-miracles-saved-surgery-womb.html. Accessed 26th May 2021.
Children’s Hospital Colorado, Fetoscopic Laser Surgery for Twin-to-Twin Transfusion Syndrome – Children’s Hospital Colorado: https://www.childrenscolorado.org/doctors-and-departments/departments/colorado-fetal-care-center/services/fetoscopic-laser-surgery/. Accessed 26th May 2021.
Sago, H. et al (2018) Fetoscopic laser photocoagulation for twin–twin transfusion syndrome - The Journal of Obstetrics and Gynaecology Research: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969296/. Accessed 26th May 2021.
Akkermans, J. (2017) Impact of Laser Power and Firing Angle on Coagulation Efficiency in Laser Treatment for Twin-Twin Transfusion Syndrome: An ex vivo Placenta Study – Fetal Diagnosis and Therapy: https://www.karger.com/Article/FullText/464323. Accessed 26th May 2021.
Ruano, R. et al (2019) Fetal surgery: how recent technological advancements are extending its applications – Expert Review of Medical Devices: https://www.tandfonline.com/doi/full/10.1080/17434440.2019.1641404. Accessed 26th May 2021.