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ORIGINAL RESEARCH |
From the 1Fetal Medicine Center, Department of Obstetrics and Gynecology, Clinica Las Condes, Santiago; 2Fetal Medicine Unit, Department of Obstetrics and Gynecology, Barros Luco-Trudeau Hospital, Santiago; and 3Department of Obstetrics and Gynecology, Regional Hospital, Talca, Chile.
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ABSTRACT |
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METHODS: Cases of twin pregnancies discordant for lower urinary tract obstruction were identified from our fetal medicine database. Information on ultrasonographic findings, antenatal course, pregnancy complications, and perinatal outcome was obtained by reviewing medical records or contacting the referring obstetricians.
RESULTS: Five twin pregnancies discordant for lower urinary tract obstruction were diagnosed between 11 and 15 weeks of gestation. There were 3 dichorionic and 2 monochorionic pregnancies (1 diamniotic and 1 monoamniotic). The dichorionic pregnancies were managed conservatively, resulting in a pregnancy loss of both twins in 1 case, a single fetal death at 29 weeks in 1 case, and an early neonatal death due to lung hypoplasia of the affected twin in 1 case. On the other hand, both monochorionic twin pregnancies were managed with serial vesicocenteses. In both cases, the prenatal course was complicated, 1 by premature rupture of the membranes and the other by cord entanglement, requiring delivery at 29 and 31 weeks, respectively. Among the 4 continuing pregnancies with complete perinatal outcome, none of the affected twins survived, and the structurally normal twins were delivered between 29 and 36 weeks and discharged from the hospital in good condition.
CONCLUSION: Twin pregnancies discordant for lower urinary tract obstruction are at high risk of perinatal death and premature delivery. Prenatal intervention seems not to be associated with an improved perinatal outcome of the affected twin, but it may be beneficial in selected cases to attain viability of the unaffected twin.
LEVEL OF EVIDENCE: III
The aim of this study was to report our experience with the management of twin pregnancies discordant for lower urinary tract obstruction diagnosed in early pregnancy. Because pregnancy termination is not an option according to the current law in our country, this study may provide useful information about the natural history of the disease, which may be helpful for counseling couples facing this unusual complication.
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PATIENTS AND METHODS |
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RESULTS |
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In all 3 dichorionic pregnancies, the parents declined prenatal intervention and were managed conservatively. One of these pregnancies miscarried before 20 weeks. In the second case, megacystis of 28 mm was detected at 13 weeks in 1 twin, leading to spontaneous rupture of the bladder and urinary ascites at 15 weeks. This progressed to massive abdominal distention, marked chest compression, and fetal death at 29 weeks. The healthy twin was electively delivered at 33 weeks after documentation of abnormal coagulation profile studies in the mother. The neonate weighed 2,088 g, and the neonatal course was complicated by enterocolitis and hyperbilirubinemia, but subsequently did well and was discharged on day 32. In the third case, dysplastic kidneys resulting in poor renal function, oligohydramnios and a "floppy" collapsed bladder were documented from 16 weeks onwards. An elective cesarean delivery was performed at 36 weeks of gestation. The healthy female twin weighed 2,732 g and was discharged on day 5 in good condition. The affected twin weighed 1,212 g, exhibited features of Potter syndrome, and died shortly afer delivery because of severe pulmonary hypoplasia.
Among the 2 monochorionic pregnancies, 1 was diamniotic and 1 was monoamniotic. In both cases, placement of a vesicoamniotic shunt was considered to be technically difficult, because of an extensively anterior placenta, thereby hindering infraumbilical access to the fetal bladder of the affected twin. Both cases were therefore managed with serial vesicocenteses to prevent uterine overdistension and chest compression leading to premature delivery and fetal death, respectively.
The monochorionic–diamniotic pregnancy was diagnosed at 12 weeks, at which time the abnormal twin had megacystis measuring 22 mm. At referral 4 days later, the bladder had enlarged to 29 mm (Fig. 1), and the first bladder aspiration of 12 mL was performed at that time to decrease fetal intra-abdominal pressure and to attempt to trigger voiding.8,9 A follow-up scan 1 week later, however, demonstrated generalized subcutaneous edema and urinary ascites in the abnormal twin. Serial vesicocenteses combined with abdominal aspiration at 16, 22, and 25 weeks yielded 330, 710, and 945 mL of fluid, respectively. The pregnancy proceeded until 29 weeks, at which time the woman presented with rupture of membranes, which led to a premature vaginal delivery. The abnormal twin died shortly after delivery. The second twin weighed 940 g, and the neonatal course was complicated by bronchopulmonary dysplasia. The infant recovered well and was discharged from the hospital in good condition on day 84, free of oxygen dependence. At 6 months of age he was doing well, with no evidence of bronchopulmonary disorders or neurodevelopmental delay.
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The monochorionic–monoamniotic pregnancy was diagnosed at 11 weeks, at which time megacystis measuring 10 mm was noted in 1 twin. Follow-up scan at 13 weeks demonstrated enlargement of the bladder to 29 mm and a nuchal translucency thickness of 3.6 mm. Severe enlargement of the fetal bladder was documented at 16 weeks. Serial vesicocenteses were carried out weekly from 22 weeks, yielding 865, 490, 850, 780, 890, 795, 1210, 1030, and 590 mL, respectively. The twins were electively delivered by cesarean at 31 weeks due to cord entanglement. The abnormal twin weighed 1,334 g, had prune belly syndrome, and died soon after birth due to severe pulmonary hypoplasia. An absent right leg and right-hand oligodactyly with syndactyly, undiagnosed prenatally, were noted at birth. The structurally normal twin weighed 1,440 g, and the neonatal course was complicated by respiratory distress syndrome and sepsis. He was discharged from the hospital on day 45 in good condition. Follow-up to 1 year has shown mild neurodevelopmental delay.
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DISCUSSION |
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Our study demonstrates the poor perinatal outcome in twin pregnancies discordant for lower urinary tract obstruction, not only for the affected fetus but also for the structurally normal twin. In contrast to the previous study,5 all of our cases were diagnosed before 16 weeks, 4 of which were detected in the first trimester as part of nuchal translucency screening for chromosomal anomalies. This highlights the importance of incorporating the first-trimester scan to measure nuchal translucency in the general population, because an additional advantage of this method is the early detection of severe congenital anomalies.7 Indeed, detection of megacystis at this gestational age is straightforward.7,10 If the bladder diameter in the first trimester is greater than 15 mm, as in 3 of our cases, the condition is invariably associated with progressive obstructive uropathy and, therefore, with poor prognosis.11 In addition, accurate chorionicity determination in twin pregnancy at this stage is easy to accomplish,12 which also has significant implications for subsequent pregnancy management. However, the main advantage of early prenatal diagnosis is the possibility of embryoreduction in pregnancies with a dichorionic placentation. Selective termination of pregnancy after 16 weeks is associated with a 3-fold increase in risk compared with embryoreduction before 16 weeks, with an inverse correlation between the gestational age at feticide and the gestational age at delivery.13
The prenatal management of a twin pregnancy discordant for lower urinary tract obstruction has not been fully established due to the small number of cases currently available in the medical literature. In dichorionic pregnancies, a sensible option is selective feticide.13,14 However, in countries such as ours, elective termination of the pregnancy is not permitted. Initially, we considered that expectant management would be the best option for dichorionic pregnancies, because prenatal invasive intervention has its inherent risks that will invariably affect both twins. On the other hand, in the event of spontaneous death of 1 twin, one would not expect any direct potential consequences to the healthy cotwin. However, as 2 of our cases illustrated, this is not necessarily true, because 1 of the pregnancies miscarried soon after the diagnosis and another was complicated by late fetal death and subsequent maternal coagulopathy.
Management in monochorionic pregnancies, on the other hand, is more problematic. Selective feticide is not an option, because the standard procedure of intracardiac injection of potassium chloride is complicated by the presence of placental vascular anastomoses between the twins.13,14 Recently, the use of cord occlusion techniques has been advocated, but these procedures need to be performed at more advanced gestational ages and remain associated with high rates of pregnancy loss.15,16 We managed our 2 monochorionic pregnancies with serial vesicocenteses in an attempt to prevent fetal death secondary to chest compression and to reduce the risk of uterine overdistension and premature delivery. Nevertheless, both pregnancies were complicated, 1 by rupture of the membranes and the other by cord entanglement, requiring prompt delivery at 29 and 31 weeks, respectively. Both affected twins died shortly after delivery, and both structurally normal fetuses survived but with complications.
In monochorionic twins, the possibility of renal transplant is an appealing option, because one twin may be the perfect donor in these cases. However, several clinical and ethical issues complicate a potential transplant procedure. First, the abnormal twin may have additional malformations which may not be detected antenatally, as demonstrated in 1 of our cases. Second, the association between lower urinary tract obstruction and pulmonary hypoplasia seems difficult to prevent. Given its strong association with poor postnatal outcome, the prognosis and therefore potential benefit given to the affected twin is currently difficult to assess. It was initially considered that the presence of a normal amniotic fluid volume in one sac prevents the development of pulmonary hypoplasia in the cotwin with oligohydramnios secondary to renal pathology.17,18 However, this may only be true for fetuses with renal agenesis, in which there is no additional abdominal distension.18 In contrast, in fetuses with severe lower urinary tract obstruction and megacystis, the abdominal overdistension is often associated with severe chest compression with resulting pulmonary hypoplasia.19,20 Indeed, in neither of our monochorionic twin pregnancies was pulmonary hypoplasia prevented despite normal amniotic fluid in the normal cotwin and serial bladder aspirations in the affected fetus. Last, the impact of the long-term consequences of bladder dysfunction on the quality of life of the affected twin must be considered.21,22
In conclusion, twin pregnancies discordant for lower urinary tract obstruction are associated with a poor perinatal outcome for both the abnormal and the structurally normal fetuses. In countries where elective termination of pregnancy is legal, selective termination in dichorionic twins may be a sensible option to prevent prematurity of the healthy twin. In monochorionic twins, however, serial vesicocenteses or placement of a vesicoamniotic shunt may help the normal twin attain viability, although the problems of extreme prematurity will most likely complicate its postnatal course.
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Footnotes |
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Corresponding author: Waldo Sepulveda, MD, Fetal Medicine Center, Clinica Las Condes, Casilla 208, Santiago 20, Chile; e-mail: fetalmed{at}yahoo.com.
doi:10.1097/01.AOG.0000175833.65983.ee
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This article has been cited by other articles:
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  A. Casasbuenas, A. E. Wong, and W. Sepulveda Nuchal Translucency Thickness in Monochorionic Multiple Pregnancies: Value in Predicting Pregnancy Outcome J. Ultrasound Med., March 1, 2008; 27(3): 363 - 369. [Abstract] [Full Text] [PDF]
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