Fetal surgery is a branch of maternal-fetal medicine that covers many surgical techniques used to treat unborn babies with congenital disabilities while still in the Uterus. The three main types of fetal surgery are fetoscopic surgery, open fetal surgery, and surgery after a cesarean section before the umbilical cord is cut. Different methods of fetal surgery are used to treat various defects, and they depend on the circumstances. Different procedures and techniques for different defects such as Spina Bifida and Congenital diaphragmatic hernia and Twin to twin transfusion syndrome will be explained in this article.
What is Fetal Surgery?
According to the Mayo Clinic, Fetal Surgery is a procedure performed on an unborn baby (fetus) in the uterus to help improve the long-term outcome of children with congenital disabilities. The early intervention allows for improved outcomes of life-threatening birth defects by focusing on treating conditions before birth.
Although fetal surgery is an essential development in modern medicine, there are some risks posed to the mother and the fetus. Hazards include a potential failure to treat the defect, the possibility of fetal death, early labour, operative complications, and uterine rupture.
Fetal surgery may be performed in different ways, and the method is chosen to reduce the risks for the fetus and the mother. Medicine Net explains the three main methods of fetal surgery; Fetoscopic Surgery, Open Fetal Surgery, and Surgery performed after a cesarean section.
Fetoscopic Surgery : Using a scope to enter the uterus through a small surgical opening. Corrects birth defects without major incisions or removing fetus from the womb.
Open Fetal Surgery : Requires hysterectomy (opening of uterus). The area of the fetus to be operated is partially removed from the uterus. After surgery, the fetus is removed and the uterus is closed.
Surgery may also be performed after a C-section but before the umbilical cord is cut. This is so the fetus is sustained by the mother when the fetus has a congenital defect blocking the airway. By the time the cord is cut, the baby should be able to breathe on its own.
But what about tumours? Medicine Net makes it clear that tumours may be treated before birth using ultrasound, radiofrequency ablation, which cuts off blood supply to the tumour and hinders the tumour growth just enough so that the fetus survives delivery and can get the tumour removed after birth.
Procedures and Techniques in fetal surgery: Spina Bifida
Spina Bifida, Also known as myelomeningocele (MMC), is a birth defect to the central nervous system that causes significant lifelong morbidity with no cure. Scott Adzick explains how MMC is characterized by protrusion of the meninges and spinal cord through open vertebral arches leading to lifelong paralysis. MMC patients may also experience cognitive dysfunction, bowel and bladder dysfunction, and orthopedic disabilities.
MMC is caused by the neural tube's failure or mesenchymal closure at the caudal neuropore in the uterus while the fetus is developing. This may cause further destruction to exposed neural tissue by trauma or amniotic fluid.
Until 15 years ago, MMC was treated with surgical closure of the spinal canal at birth with lifelong supportive care.
Mothers who continue a pregnancy must prepare for a child with significant care and high medical expenses -- 14% of all spina bifida neonates do not survive past age 5 with -- 35% of spina bifida neonates do not survive in those with brainstem dysfunction -- 70% of patients have an IQ above 80 -- only 50% can live independently as adults.
80% require shunts with 46% complications of shunts within the first year of placement.
Almost all MCC patients have the Arnold-Chiari II malformation -- the descent of cerebellar vermis through the foramen magnum (can lead to brain stem compression), elongation of medulla kinking displacement of the spinal cord, and obliteration of cisterna magna.
Image Courtesy of Upright Doctor
The Cisterna Magna is located between the medulla and the cerebellum. In Chiari patients, since the cerebellum is pushing down, that layer is destroyed. In the image below, you can see how the cerebellum descends downwards.
Image Courtesy of Keystone Chiropractic and neuroplasticity
In an issue of the Clinics of Perinatology, it is stated that the fetoscopic repair of MMC was trained to maximize the fetus's potential benefit and minimize risk and morbidity to the mother. Fetoscopic repair would be abandoned in favor of open fetal repair since fetoscopic was more difficult to perform and closing of the defect was incomplete and required further reoperations after birth.
The Vanderbilt group found that MMC patients who had undergone open fetal surgery had improved hindbrain herniation and significantly lower need for shunting (from 91% decreased to 59%).
Saadai and Farmer say, "Children's Hospital of Philadelphia confirmed findings of reversal of hindbrain herniation and improvement in the Chiari malformation in patients who had undergone open fetal repair." A distal neurological function may improve increase in some with MMC open fetal surgery.
According to the Clinics of Perinatology, the future of MMC fetal surgery can use biomaterials (gelatin microspheres, nanofibrous scaffolds) to maximize prenatal MMC closure and the use of murine neural stem cells to repair neurological function. These developments are essential to decrease risk, and that's why another possibility is to use less invasive surgery methods. Methods continue to be investigated as they have reduced maternal morbidity compared to open fetal surgery.
Image Courtesy of Journal of Neurosurgery, pediatrics
Procedures and Techniques in fetal surgery: Congenital Diaphragmatic Hernia -- fetal endoluminal tracheal occlusion (FETO)
The Guardian explains, "CDH is rare. About one in 4,000 unborn babies will develop a hole in their diaphragm, the thin sheet of muscle separating the chest from the abdomen, which can allow the stomach, liver or bowels to move up through the gap into the chest cavity, squashing the lungs and, in the worst cases, leaving them too underdeveloped to allow breathing after birth."
1/3 of the cases can be treated with the fetoscopic tracheal occlusion developed by Dr. Nicholaides. A fascinating documentary on Netflix is "The Surgeon's cut" where you can see Dr. Kypros Nicholaides create and perform the surgery.
A miniature latex balloon is inserted topically through the fetus's mouth and delicately placed and inflated in the windpipe. It is left for 26-28 weeks before being removed at around 35 weeks. This traps fluid in the baby's lungs that would usually escape through the baby's lungs, forcing the lungs to expand and develop. This procedure can increase survival rates from 15-20% to about 50%. This means that babies with severe CDH can be safely delivered (they may need to undergo more surgery to correct hernias and internal organs' positions after birth).
An article published in Gynecological Surgery says that without the fetal endoluminal tracheal occlusion (FETO) surgery, surviving patients may suffer from medium and long-term respiratory dysfunction and gastroesophageal reflux. As fluid is blocked from escaping through the fetus' mouth, the lungs are stretched, which leads to proliferation and increased growth of the airways and pulmonary vessels.
This surgery is performed under sono-endoscopic guidance, meaning it's like ultrasound with an endoscope. Landmarks for balloon insertion are used to guide the positioning of balloons. The milestones are in progression: the tip of the nose, philtrum, tongue, the raphe of the palate, uvula, epiglottis, and ultimately the vocal cords. Once the balloon is properly positioned guided by the fetoscope, isotonic saline is used to fill the balloon and the balloon is detached. The FETO procedure usually takes around 20 minutes, ranging from 3 to 90 minutes, and depends mainly on operator experience, the position of the fetus, and risk of chorionic membrane separation and amniorrhexis.
Image is Courtesy of Gynecological Surgery
Ultrasounds every 1 to 2 weeks are performed until the balloon is removed. The fetus is evaluated for growth, movement, wellbeing. Amniotic fluid is measured to exclude polyhydramnios, and membranes are inspected for separation.
The balloon can be removed with fetoscopy (67% of cases) or punctured (21% of cases). Where fetoscopic removal is not possible, tracheoscopy removal is performed -- fetal head and shoulders are delivered during placental circulation (see below). Placental circulation is performed in 10% of cases.
Image is Courtesy of Gynecological Surgery
The Guardian explains how fetoscopic laser treatment developed by Dr. Nicolaides is used to coagulate blood vessels shared by identical twins with twin to twin transfusion syndrome. TTTS occurs when the blood vessels are shared between twins, but one baby receives more blood than it gives up, putting it's twin and itself at risk. As a result, one baby is larger than the other, and one twin has an insufficient blood supply.
In the Netflix documentary "The Surgeon's cut", mentioned previously, you get to see Dr. Nicolaides perform this surgery as well.
In the Journal of Obstetrics and Gynaecology Research, we learn that treatment is a minimally invasive procedure performed with ultrasound guidance.
Image is Courtesy of the Journal of Obstetrics and Gynaecology Research
There are high survival rates and low rates of neurological complications.
Survival of both twins = 61.9%
Survival of one twin at six months of age = 90.1%
The Solomon technique is the entire vascular equator's coagulation to reduce residual anastomoses that causes recurrence of TTTS or twin anemia-polycythemia sequence (TAPS). Since identical twins share a placenta, TAPS occurs when there is an imbalance of red blood cells.
Image is Courtesy of the Journal of Obstetrics and Gynaecology Research
Image is Courtesy of John Hopkins Center for Fetal Therapy
Selective coagulation is when unnecessary coagulated vessels result in the reduced vascular territory, leading to an increased risk of fetal death. Therefore, only communicating vessels between twins are coagulated. This reduces donor hypotension. The donor is the baby that is receiving less blood.
FLP (fetoscopic laser photocoagulation) is performed using both selective and nonselective coagulation. Taken from a total of 34 studies over the past 25 years, following the solomon and selective coagulation technique, this procedure has increased survival of both twins from 35% to 65% and for at least one twin from 70% to 88%.
Although FLP improves the survival rate of TTTS, neurological abnormalities may still be present (ex. Cerebral palsy, severe developmental delay, blindness, and deafness)
Severed cerebral injury occurrence ranges from 2.9% to 6%, and neurodevelopmental impairment occurrence ranges from 11.1% to 13.3%.
Complications include preterm premature rupture of membranes (pPROM), leading to preterm labour -- a common complication in FLP. Chorioamiotic membrane separation occurs in 20% of patients following FLP. No therapies currently to prevent pPROM yet.
Featured Image is Courtesy of Wix
Article Contributors: Ashley Chen, Edie Whittington
Article Editor: Maria Giroux