THE FETUS WITH AN ABDOMINAL WALL DEFECT

Arlet G. Kurchubasche
Division of Pediatric Surgery and Program in Fetal Medicine

Brown Medical School and Hasbro Children's Hospital

*Reproduced with permission from Medicine & Health/Rhode Island 2001;84:159-161.
The May 2001 issue of this journal was published in conjuction with the 2nd Annual Frank G. DeLuca Lectureship in Pediatric Surgical Sciences, entitled "The Smallest Patient: Foundations in Fetal Medicine," organized by the Brown Medical School Program in Fetal Medicine

INTRODUCTION

Antenatal detection of abdominal wall defects has impacted the perinatal care of both the expectant mother and of the fetus. Prenatal referral to tertiary care centers that can provide for the surgical needs of the infant has also allowed for focused management from the obstetric perspective to identify the unique problems associated with these pregnancies. With advances in maternal-fetal medicine, obstetrics and neonatal surgery and the increasing availability of in utero interventions it is essential to determine which current therapeutic interventions result in optimized outcomes and where future investigational efforts should be directed. In this age of information technology we need to provide expectant parents with reliable and useful information.

Although not specifically elucidated, the etiologies of omphalocele and gastroschisis are likely widely discrepant, based not only on the spectrum of associated anomalies in the fetus but also the differing demographics of the maternal populations. This dichotomy extends to the postnatal period in terms of operative management and morbidity and mortality. Vital to appropriate counseling and stratification of risk therefore, is the ability to make a specific diagnosis for a fetus with an abdominal wall defect.
On sonogram, the presence of a defect to the right of the umbilicus, with eviscerated bowel that is not contained within a membrane is consistent with gastroschisis. The fetus with omphalocele has an absent abdominal wall subjacent to the cord insertion site with a membrane usually containing the protuberant liver and eviscerated intestine. Localization of the defect is helpful particularly to avoid diagnostic errors associated with the rare ruptured omphalocele that masquerades as gastroschisis.

OMPHALOCELE

Approximately 20 % of anterior abdominal wall defects are omphaloceles. Antenatal evaluation of the fetus with omphalocele focuses on the associated conditions. These may include lethal chromosomal anomalies (particularly trisomy 13 and 18), congenital cardiac defects, other upper midline/thoracic defects such as in the Pentalogy of Cantrell (sternal, diaphragmatic, pericardial defects with ectopia cordis and omphalocele) or the lower midline OEIS complex (omphalocele, exstrophy, imperforate anus, spinal defect). Other associated conditions include Beckwith-Wiedeman syndrome, cleft lip/palate and cryptorchidism. The incidence of associated anomalies (excluding intestinal malrotation, which is uniformly present in those with large defects) is reported as high as 69%. 1

In a recent study of 23 fetuses or infants with the pre or postnatal diagnosis of omphalocele, 21 fetuses had an antenatal diagnosis made by 18 weeks gestation.2 In 18 pregnancies, the diagnosis was correct. (two false positives, and 3 false negatives). Associated anomalies were correctly identified in 12 but incorrectly reported in 8. There were 13 terminations including 2 trisomy 18s and one trisomy 13. Two fetal deaths followed amniocentesis. Of the 10 live births, 9 had their ventral defect repaired with a one-year survival rate of 89%.
When providing antenatal counseling to parents, this information needs to be relayed within the appropriate context. Those liveborn infants with an omphalocele and without additional life-threatening anomalies have a lesion that is amenable to surgical therapy with good outcomes.

SURGICAL CONSIDERATIONS

Repair of the omphalocele provides specific challenges to the infant and surgeon, but in over 50% cases, a primary repair can be achieved. The spectrum of defects ranges from the "hernia of the cord", which could potentially be reduced and closed at the bedside, to omphalocele minor with a fascial defect of up to 4cm and to omphalocele major typically with defects from 4 cm to 8 cm. Given the closed nature of the defect, with liver and intestines enclosed in peritoneum and amnion, postnatal management can initially focus on the potentially lethal malformations. Once these have been identified and addressed, usually within 24-48 hours, decisions can be made regarding surgical closure. In contrast to gastroschisis, the intestinal tract is usually normal, but the size of the defect and the liver may provide major impediments to complete fascial approximation. Viscero-abdominal disproportion refers to the discrepancy between the current abdominal capacity and the extra-abdominal volume of eviscerated organs. Aggressive reduction into the abdomen may result in compromised hepatic or visceral perfusion requiring urgent decompression. Infants with very large defects may require staged closure to allow for gradual expansion of the abdominal wall. This may involve: 1) primary coverage with skin flaps with subsequent ventral hernia repair, 2) staged closure using a silo, with or without excision of the sac or 3) topical treatment may induce sufficient wound contraction with epithelialization to achieve closure for subsequent ventral hernia repair. Infants with lethal cardiac or chromosomal disorders can be managed nonoperatively with topical therapy.
Extended hospital courses and complications are primarily limited to those with defects measuring greater than 8 cm in diameter. Even in this group the surgical mortality was only 8%.1 In the absence of associated severe anomalies these infants can have an uncomplicated course with a normal long-term quality of life. Less optimal outcomes are determined primarily by the nature of the chromosomal defect and the complexity of associated cardiac and other organ system defects. With improvements in the reconstruction of these complex anomalies, this will further reduce mortality and improve quality of life. As such, the antenatal assessment by a multidisciplinary team including perinatalogists, neonatologists, geneticists and cardiologists and surgeons will have critical impact on the decision to continue the pregnancy.

GASTROSCHISIS

The perinatal management of infants with gastroschisis is quite distinct from those with omphalocele. Whereas the size of the ventral defect and associated anomalies dictate prognosis in omphalocele, the relevant parameters in the infant with gastroschisis are related to the condition of the newborn and the intestine. Short bowel syndrome with its attendant risks remains one of the significant complications of the diagnosis of gastroschisis.
Fetuses with gastroschisis tend to be small for gestational age and are born to young primiparous women, often after preterm labor. Although the specific factors leading to this congenital malformation have not been elucidated, the focus has rested on environmental and potentially nutritional factors. Studies from the California birth defects monitoring program have proposed that a low prepregnancy body mass may represent a risk factor for offspring with gastroschisis. 3 These investigators suggest that abnormal levels of 3 nutrients (low alpha carotene, low total glutathione and high nitrosoamines) are potential candidates for further investigation.4 Much of the clinical and basic science investigation into gastroschisis has tried to identify factors that contribute to the intestinal wall thickening and formation of a peel over the serosal surface, the findings that most impede reduction of the intestine into the abdominal cavity and that are thought to contribute to the dysmotility encountered postoperatively. Conventional wisdom attributes these changes to exposure to amniotic fluid, although not all infants with gastroschisis exhibit the serosal peel. A recent animal study has sought to differentiate between urinary and gastrointestinal waste products in amniotic fluid, and has implicated components of meconium as the more significant sources of inflammation.5 Saline amnioinfusion performed both in an animal model and in a small cohort of patients with gastroschisis and severe oligohydramnios was found to be associated with less inflammatory peel as compared to non-amnioinfused infants with gastroschisis.6, 7,8 These concerns have been the premise for advocating early delivery of these infants, particularly when visceral distension is noted to be progressive, suggesting an underlying intestinal obstruction. Vascular etiologies of the intestinal atresias and of the inflammatory changes have been proposed and may be related to constriction of the mesentery by the approximating fascial edges as evidenced in fetuses born with antenatal detection of gastroschisis and consequent jejunal atresia or congenital SBS without abdominal wall defect. Based on the premise that the amniotic insult to the intestine is cumulative and a function of time - preterm induction of labor was considered prudent so as to enhance the ability to achieve primary closure. In the current literature, no randomized prospective series exists to support this intervention and preliminary evidence from our series of inborn patients in whom no attempt was made to induce early labor suggests that there is no beneficial effect to early delivery and that term infants recover as well if not better than their preterm counterparts. Premature labor however, remains a feature associated with gastroschisis and may not be an avoidable event in approximately 30% of patients. 9 Debate in the perinatal management of gastroschisis has also revolved around the mode of delivery with Cesarean section advocated by multiple centers. Vaginal delivery, however, has been shown to be safe in multiple recent studies and general consensus would indicate that a trial of labor is appropriate and that Cesarean section should be reserved for obstetric indications only. 10,11,12

OPERATIVE MANAGEMENT

Antenatal counseling by a pediatric surgeon will focus on the immediate surgical care to be delivered to an infant with exposed viscera that are at risk for further vascular compromise. The options for acute management range from operative intervention either in the delivery room or in the operating room. The exposed intestine has a variable degree of inflammatory peel. When extensive, this may prohibit identification of an intestinal atresia. In virtually all cases, the bowel length appears shortened, with a thickened mesentery. Sedation and paralysis with expansion of the lateral abdominal wall may enable complete reduction of the viscera and permit fascial closure. If not feasible then a silo, typically spring-loaded and no longer requiring fascial sutures, can be inserted. This can also be accomplished at the bedside with minimal sedation. A recent prospective trial of routine insertion of a silo as compared to emergency operating room closure provided favorable results for the routine insertion of the silo with reduced number of days to extubation, to full feeds and to home discharge. 13 The postoperative course of these infants is typically marked by a prolonged ileus, during which they rely on parenteral nutrition support. When intestinal continuity has not become evident after several weeks, contrast studies are performed to delineate the anatomy and to exclude the possibility of an occult atresia. By this time much of the inflammatory peel, which may have been present initially, will have resolved and now allows for intestinal resection and anastomosis to establish continuity. Short bowel syndrome may occur as a consequence of atresias or after postnatal hypoperfusion insults to the intestine or even florid necrotizing enterocolitis. With appropriate nutritional management focusing on measures to avoid cholestasis, these infants can be transitioned to full enteral feedings.
The use of promotility agents has not been shown to be useful in expediting normal motility.12 Motility agents and acid suppression therapy however may play a role in a significant number of infants who have evident gastroesophageal reflux.14 Although both omphalocele and gastroschisis are associated with intestinal malrotation, the occurrence of gastroesophageal reflux during the first year of life is reported to be higher in omphalocele than gastroschisis.

REFERENCES

1. Dunn JCY, Fonkalsrud EW. Improved survival of infants with omphalocele. Am J Surg 1997; 173: 284-287.
2. Holland AJ, Ford WD, Linke RJ et al. Influence of antenatal ultrasound on the management of fetal exomphalos. Fetal Diagnosis and Therapy 1999;14: 223-8
3. Lam PK, Torfs CP, Brand RJ. A low pregnancy body mass index is a risk factor for an offspring with gastroschisis. Epidemiology 1999; 10: 717-721.
4. Torfs CP, Lam PK, Schaffer DM et al. Association between mother's nutrient intake and their offspring's risk of gastroschisis. Teratology 1998; 58: 241-50.
5. Akgur FM, Ozdemir T, Olguner M et al. An experimental study investigating the effects of intraperitoneal human neonatal urine and meconium on rat intestines. Research in Experimental Medicine 1998; 198:207-213.
6. Luton D, de Lagausie P, Guibourdenche J et al. Influence of amnioinfusion in a model of in utero created gastroschisis in the pregnant ewe. Fetal Diagnosis and Therapy 2000;15: 224-8.
7. Sapin E, Mahieu D, Borgnon J et al. Transabdominal amnioinfusion to avoid fetal demise and intestinal damage in fetuses with gastroschisis and severe oligohydramnios. J Pediatr Surg 2000; 35: 598-600.
8. Luton D, de Laugausie P, Guibourdenche J et al. Effect of amnioinfusion on the outcome of prenatally diagnosed gastroschisis. Fetal Diagnosis and Therapy 1999;14:152-5.
9. Anteby EY, Sternhell K, Dicke JM. The fetus with gastroschisis managed by a trial of labor: antepartum and intrapartum complications. Journal of Perinatology 1999;19:521-4
10. How HY, Harris BJ, Pietrantoni M et al. Is vaginal delivery preferable to cesarean delivery in fetuses with a known ventral wall defect? Am Journal of Obstetrics and Gynecology 2000;182:1527-34.
11. Snyder CL. Outcome analysis for gastroschisis. J Pediatr Surg 1999; 34: 1253-6.
12. Kumar RK, Shi EC Duffy B. Cisapride and Caesarian section: their role in babies with gastroschisis. Journal of Pediatrics and Child Health 1999; 35:181-4.
13. Minkes RK, Langer JC, Mazziotti MV et al. Routine insertion of a silastic spring-loaded silo for infants with gastroschisis. J Pediatr Surg 2000;35: 843-6.
14. Koivusalo A, Rintala R, Lindahl H. Gastroesophageal reflux in children with a congenital abdominal wall defect. J Pediatr Surg 1999;34: 1127-9.

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MANAGEMENT OF TTTS


Once diagnosed, untreated TTTS results in morbidity and mortality that exceeds 70%.[3] Despite enthusiasm for different modalities, treatment of TTTS is associated with survival rates of only 60-70%. Even more troubling is the increased incidence of cerebral palsy and other cerebral impairment (from 20-40%) in the surviving co-twin when one of a set of monochorionic twins dies in utero.[4, 5] Several treatment modalities have been used to treat TTTS. Those receiving the most attention include serial amnioreduction, septostomy, and fetoscopic laser ablation of chorioangiopagus vessels (FLOC).

AMNIOREDUCTION


Amnioreduction is the removal of large quantities of amniotic fluid from the polyhydramniotic sac of the recipient twin. This is accomplished using an 18 or 20 gauge needle under ultrasound guidance and is performed from one to several times. Although amnioreduction does not address the postulated cause of TTTS, it is postulated to result in decreased pressure on the transplacental vascular anastamoses, which increases placental compliance, thus reducing the preload and afterload in the hearts of both twins.[6] The reduction in intrauterine volume also appears to decrease the incidence of preterm labor, a major contributor to the morbidity of TTTS. Proponents of amnioreduction point to it's simplicity and success rates; one recent trial of aggressive amnioreduction reported 57% survival of both twins at 24 months of age and 70% survival at 24 months of age of at least one twin.[7] Preterm premature rupture of membranes complicates 8% of pregnancies treated with serial amnioreduction.[8]

SEPTOSTOMY


Septostomy (deliberate creation of a defect in the membrane separating the two twins) has been proposed as a method to equalize the pressures in the twins' amniotic sacs. In this technique a 20 or 22 gauge needle is introduced to the uterine cavity using ultrasound guidance in such a way as to deliberately breach the amniotic membrane overlying the smaller oligohydramniotic sac. A recent study of 12 patients with severe TTTS treated with intentional septostomy yielded 75% survival of both twins to delivery and 92% survival of at least one twin.[9] The authors, and others, postulate that deliberate septostomy results in an equilibration of amniotic fluid volumes around both twins as a result of hydrostatic pressure differences between the sacs that may be too small to measure. As in amnioreduction this technique does not directly address the postulated cause of TTTS, the transplacental vascular anastamoses, but offers temporizing measures in an attempt to prolong the pregnancy to the point where survival ex utero is possible.

FETOSCOPIC LASER ABLATION OF CHORIOANGIOPUS VESSELS (FLOC)


Fetoscopic laser ablation of chorioangiopagus vessels (FLOC) is the only proposed intervention for TTTS that directly addresses the postulated etiology of TTTS, that is, the transplacental vascular communications. This technique, first described by De Lia et al,[10] uses a fetoscopically-directed YAG-neodynium laser to photocoagulate those transplacental vascular communications felt to be contributing to the TTTS. Initial use of this technology involved ablation of all vessels crossing the vascular equator of the placenta, but more recently there has been more selective ablation involving only those vessels thought to be contributing to the TTTS. Data from recent series indicate 69% survival of both twins, 82% survival of at least one twin, and 4.3% significant handicap in survivors of an in-utero demise.[11]

2 survivors At least 1 survivor Spontaneous abortion Double fetal loss Neonatal death Abnormal brain scan survivor(s) Birth weight (donor) Birth weight (recipient)	FLOC 42% 79%* 12% 3%* 6% 6%* 1750 g* 2000 g	Serial amnioreduction 42% 61%* 7% 19%* 14% 18%* 1145 g* 1560 g
Table 2: Comparison of FLOC and amnioreduction.

CHOICE OF TREATMENT


Direct comparison of the efficacy of the different available interventions has not been accomplished. Comparisons extant in the TTTS literature typically compare case series using one intervention with case series using a different intervention. One such recent comparison [12] compared outcomes in 73 cases of severe TTTS treated with FLOC in one center with 43 cases of severe TTTS treated with serial amnioreduction in another center. (Table 2; * denotes p < 0.05)
There are currently two randomized trials underway in attempts to determine the most effective intervention for treatment of TTTS. One is the EUROFETUS consortium (www.eurofetus.org) that randomizes cases diagnosed with severe TTTS between serial amnioreduction and FLOC. The other trial is coordinated at the University of North Carolina [13] and is randomizing between serial amnioreduction and septostomy. The relatively infrequent nature of severe TTTS cases near any one center, and the (usually) strongly held opinions of a given treatment team has rendered recruitment into these trials more time-consuming than might have been originally anticipated.
Timing the intervention is of paramount importance in the treatment of TTTS. As in any medical procedure, the risks of the procedure itself must be weighed against the risk of the disease that is being treated. The known risks of any of the interventions for TTTS (preterm premature rupture of membranes, infection, preterm labor, placental abruption, hemorrhage and fetal death) must be acknowledged in deciding when to intervene. Quintero et al [14] presented a classification schema based on their experience (Table 3.) The group recently published their results following FLOC using their staging schema.[15] (Table 4.)

COMPLICATIONS OF TTTS


Consideration of the morbidity following diagnosis and treatment of TTTS is of equal importance to survival. In cases of TTTS treated with serial amnioreduction that are complicated by in-utero demise of one twin, neurological handicap is seen in approximately 30% of survivors [16]. Cases of TTTS treated with FLOC that are complicated by in-utero demise of one twin experience neurological handicap in 4.2% [17] (compared with the 18% incidence of neurological handicap seen in singleton survivors following serial amnioreduction.[12]. Taken at face value, these data suggest that while overall survival appears to differ little between the different interventions, there is a lesser risk of neurologic morbidity in survivors following FLOC than in survivors following serial amnioreduction.
There have also been reports of limb reduction anomalies and intestinal atresia associated with TTTS. Table 5 summarizes published cases of structural anomalies associated with monochorionic twinning. The etiology of these defects remains unclear. Hecher et al [18] suggested that polycythemia and an arterial steal syndrome were the probable etiology of necrotic toes detected prior to FLOC for severe TTTS. Margono et al [19] suggested that their findings of thrombosis of the transplacental vascular connections and necrosis of the right foot of the surviving twin were consistent with a thromboembolic phenomenon. Lundvall et al [20] found necrosis in the right lower leg of the recipient twin 27 days after FLOC. Post mortem examination found a thrombus in the right common iliac artery, "presumably the result of polycythemia". Scott and Evans [21] documented a case of severe TTTS managed with serial amnioreduction that resulted in 2 live twins. At time of delivery the recipient twin was found to have left lower leg necrosis that was associated with polycythemia (Hb 26.8 g/dL, Ht 89%). The authors concluded that the necrosis was the result of hyperviscosity due to polycythemia. Dawkins et al [6] reported a pregnancy with severe TTTS managed with amnioreduction x 6 over a nine week period. Delivery was at 32 weeks. The recipient twin was born with Hb 25.9 g/dL, Ht 72% and gangrene of the left lower leg. Arul et al [22] presented two cases of severe TTTS treated with FLOC. In both cases there was demise of the donor twin and in both survivors ileal atresia was noted after birth. The authors suggest three possible etiologies for these findings: hypoperfusion or hyperviscosity associated with TTTS could cause mesenteric ischemia; death of the donor could affect the hemodynamics of the survivor, causing mesenteric hypoperfusion; a shower of emboli or thromboplastins could be released into the fetal circulation. Van Allen et al [23] described two sets of monochorionic twins. The first case documented a singleton demise at 12 weeks EGA. At birth the surviving twin had cleft lip and palate and terminal limb reduction with ring constrictions of the left hand and both feet. In the other case singleton demise was documented at 18 weeks EGA. At birth the survivor was found to have ring constrictions of the left hand digits and left big toe. There was no evidence of amniotic bands in either case. The authors suggest that these findings were the result of vascular disruption in the co-twin. In our case TTTS was first diagnosed at 14 weeks and was treated with serial amnioreduction x 7. FLOC was performed at 23+ weeks EGA. Preterm premature rupture of membranes occurred at 26+ weeks EGA and cesarean delivery was at 28+ weeks. At time of delivery necrosis of the left lower extremity of the recipient was seen. The toe-heel length of the necrotic limb of 3.2 cm is consistent with 19 weeks 4 days gestation, which is prior to either the FLOC or the amnioreductions. Polycythemia was not universally seen in these cases, but is the most common finding among these pregnancies with severe TTTS affected with structural anomalies. Polycythemia could result from the elevated atrial natriuretic protein found in recipient twins and the resulting diuresis, and would lead to hyperviscosity. This hyperviscosity would result in greater incidence of thrombosis. It remains unclear why the lower extremities are more affected by such a thrombotic diathesis.

CONCLUSION


Monochorionic twins present unique challenges above and beyond those associated with multiple gestation. There have been several developments in the evaluation and treatment of twin-twin transfusion syndrome, but these twins remain at high risk. In spite of these advances, these twins are at continued risk for anomalies that appear to result from hypoperfusion. These anomalies have been seen in monochorionic twins that have undergone serial amnioreductions, FLOC or no intervention at all. This suggests that the tendency towards these defects is intrinsic to monochorionic twins suffering from TTTS, and is not related to the interventions that have been used in attempts to mitigate the impact of TTTS. The care of monoamniotic twins affected by TTTS continues to require coordinated care by a team of highly trained individuals.

REFERENCES

1. Robertson EG, Neer KJ. Placental injection studies in twin gestation. Am J Obstet Gynecol. 1983;147:170-4.
2. Blickstein I. The twin-twin transfusion syndrome. Obstet Gynecol 1990;76:714-21
3. Urig MA, Clewell WH, Elliott JP. Twin-twin transfusion syndrome. Am J Obstet Gynecol 1990;163:1522-6.
4. Cincotta RB, Gray PH, Phythian G, Rogers YM, Chan FY. Long term outcome of twin-twin transfusion syndrome. Arch Dis Child Fetal Neo 2000;83:F171-F176.
5. Pharaoh POD, Adi Y. Consequences of in-utero death in a twin pregnancy. Lancet 2000;355:1597-1602.
6. Dawkins RR, Marshall TL, Rogers MS. Prenatal gangrene in association with twin-twin transfusion syndrome. Am J Obstet Gynecol 1995;172:1055-7.
7. Mari G, Detti L, Oz U, Abuhamad A. Long term outcome in twin-twin transfusion syndrome treated with serial aggressive amnioreduction. Am J Obstet Gynecol 2000;1183:211-7.
8. Moise KJ. Polyhydramnios: problems and treatment. Semin Perinatol 1993;17:197-209.
9. Saade GR, Belfort MA, Berry DL, Bui T-H, Montgomery LD et al. Amniotic septostomy for the treatment of Twin Oligohydramnios-Polyhydramnios sequence. Fetal Diagn Ther 1998;13:86-93.
10. De Lia JE, Cruikshank DP, Keye WR. Fetoscopic laser occlusion of chorioangiopagus vessels in severe twin transfusion syndrome. Obstet Gynecol 1990;75:1046-53.
11. De Lia JE, Kuhlmann RS, Lopez KP. Treating previable twin-twin transfusion syndrome with fetoscopic laser surgery: outcomes following the learning curve. J Perinat Med 1999;27:61-7.
12. Hecher KH, Plath H, Bregenzer T, et al. Endoscopic laser surgery versus serial amniocenteses in the treatment of severe twin-twin transfusion syndrome. Am J Obstet Gynecol 1999;180:717-24.
13. Dorman K, Saade GR, Smith H, Moise KJ. Use of the world wide web in research: randomization in a multi-center clinical trial of treatment for twin-twin transfusion syndrome. Obstet Gynecol 2000;96:636-9.
14. Quintero RA, Morales WJ, Allen MH, Bornick PW, Johnson PK, Kruger M. Staging of Twin-twin transfusion syndrome. J Perinatol 1999;19:550-5.
15. Quintero RA, Morales WJ, Allen MH, Bornick PW, Johnson PK, Kruger M. Staging of Twin-Twin Transfusion syndrome. Frontiers in Fetal Health 2000;2:10-16.
16. Mahoney BV, Petty CN, Nyberg DA, Luthy DA, Hickock DE, Hirsch JH. The "stuck twin" phenomenon: ultrasonic findings, pregnancy outcome and management with serial amniocenteses. Am J Obstet Gynecol 1990;163:1513-22.
17. Ville Y, Hecher K, Gagnon A, et al. Endoscopic laser coagulation in the management of severe twin-to-twin transfusion syndrome. Br J Obstet Gynaecol. 1998;105:446-53.
18. Hecher K, Ville Y, Nicholaides K. Umbilical artery steal syndrome and distal gangrene in a case of twin-twin transfusion syndrome. Obstet Gynecol 1994;83:862-5.
19. Margono F, Feinkind L, Minkoff HL. Foot necrosis in a surviving fetus associated with twin-twin transfusion syndrome and monochorionic placenta that received no intervention. Obstet Gynecol 1992;79:867-9.
20. Lundvall L, Skibsted L, Graem N. Limb necrosis associated with twin-twin transfusion syndrome treated with YAG-laser coagulation. Acta Obstet Gynecol Scand 1999;78:49-50.
21. Scott F, Evans N. Distal gangrene in a polycythemic recipient fetus in twin-twin transfusion. Obstet Gynecol 1995;86:677-9.
22. Arull GS, Carroll S, Soothill PW, Spicer RD. Intestinal complications associated with twin-twin transfusion syndrome after antenatal laser treatment: report of two cases. J Pediatr Surg 2001;36301-2.
23. Van Allen MI, Siegel-Bartelt J, Dixon J, Zuker RM, Clarke HM, Toi A. Constriction bands and limb reduction defects in two newborns with fetal ultrasound evidence for vascular disruption. Am J Med Genet 1992;44:598-604.

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