Year : 2019 | Volume
: 24 | Issue : 1 | Page : 1--3
Progress in fetal surgery: A buoyant start or watchful reluctance? Perspectives for India
Department of Pediatric Surgery, All India Institute of Medical Sciences, New Delhi, India
Dr. Shilpa Sharma
All India Institute of Medical Sciences, New Delhi
|How to cite this article:|
Sharma S. Progress in fetal surgery: A buoyant start or watchful reluctance? Perspectives for India.J Indian Assoc Pediatr Surg 2019;24:1-3
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Sharma S. Progress in fetal surgery: A buoyant start or watchful reluctance? Perspectives for India. J Indian Assoc Pediatr Surg [serial online] 2019 [cited 2019 Jun 17 ];24:1-3
Available from: http://www.jiaps.com/text.asp?2019/24/1/1/247912
Fetal surgery started in the United States of America nearly four decades ago with a buoyant start and then moved to Europe. Although fetal medicine has started to bud in India, the foundation of fetal surgery is still in inception. The main reasons initially were lack of initiative, expertise, and infrastructure for the development of a dedicated fetal team consisting of a gynecologist, anesthetist, trained technicians, radiologist, and pediatric surgeon. There is also a persisting element of strong disbelief whether this is worth the efforts, risks, and expense while we are still struggling with inadequate antenatal diagnosis, sociocultural taboos, no financial support from the government for physical and mentally challenged children, and expanding population. For serious anomalies diagnosed before 20 weeks of gestations, parents still opt for medical termination of pregnancy. Spina bifida with gross neurological deficits is offered postnatal palliative care without any active intervention.
Fetal intervention for obstructive uropathy was first performed at the University of California, San Francisco, in 1981. However, it was suggested that fetal surgery for obstructive uropathy should be performed only in patients with severe oligohydramnios and normal-appearing kidneys.
The prenatal ultrasound development has propelled advances in prenatal diagnosis and intervention. In the best of hands, the sensitivity of two-dimensional ultrasound is around 50% at 11–14 weeks and increases to 90% with the additional second scan at 22–24 weeks.
Fetal malformations that can be treated with fetal medicine include twin–twin transfusion syndrome, acardiac twin, isolated intrauterine growth restriction, amnioinfusion for oligohydramnios associated with posterior urethral valves, and amnioreduction for polyhydramnios associated with intestinal atresias.
Open fetal surgery comprises of maternal laparotomy, followed by hysterotomy with direct exposure of the fetus. Fetal surgery has been done for congenital diaphragmatic hernia (CDH), constrictive amniotic bands, lower urinary tract obstruction, congenital lung malformations (CLMs), sacrococcygeal teratoma, and myelomeningocele.
Open surgery was gradually replaced by the less invasive fetoscopy. Initially, fetoscopy was carried out only in amniotic fluid medium, using a single port with an endoscope with a working channel for a laser fiber, balloon insertion, or small bipolar forceps. The fluid medium posed limitations for surgeries requiring dissection and suturing, allowed fluctuating fetal positions, and led to lower quality of the acquired images, more so in the presence of bleeding that prevented completion of the procedure. Hence, an aerial medium was developed to allow further advances in fetal surgery.
The ex utero intrapartum treatment (EXIT) procedure utilizes deep anesthesia and uterine relaxation to maintain placental circulation preserving oxygen delivery to the neonate while complex interventions are performed to secure the infant's airway just before delivery, thereby minimizing the risk of hypoxemia. It was initially developed to reverse temporary fetal tracheal occlusion for severe CDH. The indications have expanded to severe fetal airway obstruction or high likelihood of cardiopulmonary insufficiency at birth with large cervical masses, CLMs, congenital high airway obstruction, unilateral pulmonary agenesis, and EXIT to extracorporeal membrane oxygenation in CDH. Anaesthetic considerations are critical to minimize uterine tone without compromising maternal blood pressure and fetal placental perfusion.
Ultrasound is used intraoperatively to map the placental location and select the hysterotomy site during EXIT procedures and open fetal surgeries. The transvaginal ultrasound, high-frequency transducers, and improved processing speed of the ultrasound have improved demonstration of structural abnormalities. Moreover, 3D and 4D ultrasound technologies provide real-time images and multiplanar views expanding antenatal diagnosis and fetal interventions. 4D ultrasound has been used to guide the cauterization of an umbilical cord in twin–twin transfusion syndrome. Ultrafast magnetic resonance imaging (MRI) technology acquires an MRI sequence in 20 secs, avoiding the need for fetal immobilization. Computer-based 3D reconstructive models and virtual bronchoscopies have enormous potential, especially in complex cervical malformations. If a patent airway is demonstrated, planned cesarean delivery and postnatal therapy can be chosen rather than EXIT.
Sonographic measurements such as the cystic adenomatoid malformation volume ratio (CVR) are used to risk stratify lesions and identify fetuses requiring antenatal treatment. A CVR of >1.6 has an 80% risk of developing hydrops. These high-risk microcystic lesions are initially treated with maternal betamethasone to arrest further growth of the lesion. Invasive treatments are reserved for cases of CLMs with associated hydrops including thoracoamniotic shunts in the dominant macrocyst, fetoscopic laser fulguration, and fetal resection. CDH fetuses with extremely poor prognosis with a lung–head ratio of <1.2, with survival of 0%–38%, may benefit from fetal intervention.
Fetoscopic endoluminal tracheal occlusion (FETO) has shown early promise in the treatment of severe CDH. A fetoscope is used to deploy a balloon in the fetal trachea. Tracheal obstruction prevents the egress of lung fluid that in turn stimulates lung growth. The balloon is then decompressed by ultrasound-guided needle aspiration or removed through fetoscopy at approximately 34-week gestation. Although the European investigators have shown increased survival in left CDH when compared to historical controls from their CDH registry, the initial randomized controlled trials did not show an outcome difference between FETO and standard postnatal treatment. The results of the “Tracheal Occlusion to Accelerate Lung Growth” trial, a multicenter randomized trial from December 2010 to October 2017, in Europe and North America to compare FETO versus standard watchful waiting during pregnancy are awaited (ClinicalTrials.gov Identifier: NCT01240057).
The Management of Myelomeningocele Study (MOMS) published in 2011 was a prospective randomized trial comparing the prenatal open repair of myelomeningocele with postnatal correction. The study showed that antenatal repair had 50% less need of ventriculoperitoneal shunting to treat hydrocephalus, had a significant decrease in incidence of Chiari malformation, and had twice the chance to ambulate without any support. This study established the maternal risks associated with this route, including acute pulmonary edema after surgery, need of blood transfusion, and unfavorable uterine scarring (dehiscence or very thin scar) of the surgical site, in approximately 35% cases. The full cohort data of 30-month cognitive development and motor function outcomes, published recently in 2018, validate in utero surgical repair as an effective treatment for fetuses with myelomeningocele.
The hysterotomy in open fetal surgery approach in the second trimester is usually done in the body or fundal uterine region, where the muscle fibers have a helicoidal distribution. Thus, a zone of weakness is generated and uterine rupture may be caused even by only uterine distension during the further course of pregnancy. Two groups, German and Brazilian, have thus pursued an entirely percutaneous endoscopic approach for the prenatal treatment of myelomeningocele, using fetoscopy with partial carbon dioxide insufflations with different surgical techniques., The Germans achieved neurological developmental results quite similar to the results of the MOMS study but with minimal maternal morbidity. The Brazilian technique (Skin-over-biocellulose for Antenatal Fetoscopic Repair) has obtained superior neurologic results compared to the MOMS study. They have now started using an additional bilaminar skin substitute (two layers: one silicone and one dermal matrix) for larger defects. However, premature preterm rupture of membranes occurred in 84%. Meuli et al. used distally pedicled random pattern transposition flaps for larger lesions. To prevent iatrogenic preterm premature rupture of the fetal membrane, two mussel-mimetic tissue adhesives (cT and cPEG) have been qualified as possible sealants for membrane repair.
The results of randomized controlled trial, percutaneous vesicoamniotic shunting versus conservative management for fetal lower urinary tract obstruction, have been reported in 2013. The conclusion from the observational evidence is that shunting improves perinatal survival, but the effect on long-term renal function is unclear.
In India, at the Division of Fetal Medicine, All India Institute of Medical Sciences, New Delhi, about 4–5 shunt procedures/year are carried out and 4 EXIT procedures have been done so far. Few other centers in Chennai and Bangalore are also doing occasional shunting procedures. Today, with technological advances and minimal exposure in our country, a watchful reluctance has taken over as the results are been analytically observed weighing the risks with the benefits.
To conclude, while the standard of treatment for most fetal anomalies remains planned delivery at a tertiary center with appropriate neonatal intensive care facilities, few conditions may benefit from fetal surgical intervention. As minimally invasive techniques and equipment evolve, the indications for fetal surgery are likely to expand and Indian centers should start laying foundation work for the same to have the required facilities in place in case the need arises for selected precious cases. Fetal surgery should develop hand in hand with fetal medicine.
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