Ultrasound diagnostic features of twin reversed arterial perfusion sequence

Monochorionic monoamniotic twin pregnancies

Monoamniotic twin pregnancies are rare, but early diagnosis of such pregnancies is critical, as the incidence of complications in these pregnancies is much higher than in diamniotic or dichorionic twin pregnancies. Overall, only 70% of all monoamniotic twins will survive. Furthermore, approximately half of fetal deaths in these pregnancies are because of the high incidence of fetal anomalies (15%-25%), such as twin reversed arterial perfusion sequence and conjoined twinning. Therefore, early anatomy screening in the first trimester of pregnancy is recommended. Other causes of fetal death in these pregnancies include twin-twin transfusion syndrome, tight cord entanglement, or acute hemodynamic imbalances through the large placental vascular anastomoses. After viability, fetal surveillance can be intensified, as this decreases the risk of in utero death. Both inpatient and outpatient surveillance are reasonable. If otherwise uncomplicated, monoamniotic twins should be delivered at 33 to 34 weeks' gestation. Most centers will deliver by cesarean delivery, but some continue to advocate for vaginal delivery. Lastly, neonatal morbidity is high in monoamniotic twin pregnancies and is mainly related to prematurity.

Placental pathology in trap sequence: clinical and pathogenetic implications

Twin reversed arterial perfusion sequence (TRAP) resulting in an acardiac twin is a rare occurrence. Acardia requires the presence of arterial-arterial anastomosis, with retrograde perfusion of poorly oxygenated blood from the normal twin to the acardiac twin, venous-venous anastomosis carrying blood back from the acardiac to the normal twin, and circulatory failure of the acardiac twin. Although vascular anastomoses in cases of TRAP have been well described, there is little published literature on the microscopic changes in the placenta in TRAP sequence. We report a case of monochorionic monozygotic twins with an acardiac twin, large arterial-arterial anastomosis, and direct continuity of the umbilical cord veins. The placenta showed villous immaturity, striking villous calcifications, and extensive fetal thrombotic vasculopathy of the umbilical vein of the donor twin and the chorionic plate vessels. Thrombi in the umbilical vessels of the acardiac twin have been reported, and trombi in donor twin organs have been seen after fetal demise in utero. But to our knowledge there is no previously reported thrombi in the donor twin umbilical vessels or the chorionic plate veins. This may have implications not only as a possible factor in the etiology of TRAP, but also and more important as a possible risk factor for thrombotic events in the donor twin. Further studies with clinico-pathological correlation are needed to explore this issue.

Increased nuchal translucency and pathological ductus venosus flow: two cases of TRAP sequence with different outcomes

Twin reversed arterial perfusion (TRAP) sequence develops in 1% of monozygotic twins. One normal twin (donor) provides circulation for itself and for a more or less incomplete twin (recipient) with a high incidence of mortality in the donor twin. However, if the condition is detected and treated early, one twin or two triplets may survive. The study of TRAP sequence helps to better understand the pathophysiological pathways of this condition. We present two cases of TRAP sequence seen in our center with different courses. In these cases the increased nuchal translucency thickness and the pathological ductus venosus flow pattern may have been prognostic of the pregnancy outcome.

Prenatal diagnosis of fetal heart failure in twin reversed arterial perfusion syndrome

Diagnosis of twin reversed arterial perfusion (TRAP) syndrome is a rare fetal anomaly that can be misdiagnosed on prenatal ultrasound. We confirmed the use of colour-flow Doppler for prenatal diagnosis of TRAP syndrome and used serial fetal echocardiography for non-invasive evaluation of the fetus. A patient with twin intrauterine pregnancy was referred to our centre with suspected intrauterine fetal demise following a 16 week ultrasound. Serial colour-flow Doppler ultrasonography demonstrated retrograde arterial flow in an acardiac twin. Following diagnosis of TRAP syndrome, serial fetal echocardiography was employed to follow the normal twin for signs of heart failure, including right atrial dilation, tricuspid regurgitation and pericardial effusion. When early signs of fetal heart failure were suspected a viable female infant was delivered at 32 weeks' gestation. We suggest that serial fetal echocardiography represents a non-invasive approach that can be used to follow fetal cardiac function of the normal twin in TRAP syndrome.

Sonographic examination of twins. From first trimester to delivery of second fetus

Sonographic examination is essential in the diagnosis and management of twin gestation. It assists in determining the zygosity, assessing fetal anomalies, and is integral to amniocentesis if it is necessary, determining the growth and ruling out discordance, and in intrapartum management. The management of uncommon complications with twins also requires ultrasonic survey. Considering that the incidence of multiple gestation is increasing, it would be prudent to become familiar with the use and benefit of ultrasound with twins.

Acardius acephalus after induced ovulation: a case report

An excess of structural defects occurs in monozygotic twins compared to dizygotic twins or singletons. Among these defects the acardius acephalus or chorangiopagus parasiticus is one of the most rare and severe and a possible cause of pathology to the other twin. Ovulation induction by clomiphene causes an increased frequency of multiple gestation and possibly of monozygotic multiple pregnancy. In the present report, we describe a prenatally diagnosed and autopsied case of acardius acephalus from a pregnancy established after ovulation induction by clomiphene. Approximately 1.4% of pregnancies are accomplished after use of ovulation inducing medication in the Netherlands. A possible etiological role of clomiphene justifies close monitoring of future cases.