Monochorionic (MC) twin pregnancy is a distinct entity and has certain differences from dichorionic twins due to the unique placental angioarchitecture. It is characterized by twin-to-twin transfusion syndromes (twin oligohydramnios-polyhydramnios sequence and twin anemia-polycythemia sequence), acardiac twinning, selective fetal growth restriction and congenital anomalies. Selective termination is an option in MC twins complicated by selective fetal growth restriction and discordant fetal anomaly. Fetal demise of the co-twin can occur even after uncomplicated surgery. A selective fetal termination using an intrafetal laser was performed in the case of an MC twin pregnancy complicated by twin oligohydramnios-polyhydramnios sequence and hydrocephalus in the donor twin. Fetal demise of the co-twin was observed after surgery. The placenta was examined with dye injections after abortion and showed vascular anastomoses causing unexpected fetal demise.
Monochorionic (MC) twins are a subtype of monozygotic (MZ) pregnancies and are seen in 0.3% of all pregnancies. MC diamniotic pregnancies are the most common subtype of monozygotic pregnancies and account for 70–75% of all MZ pregnancies . Approximately 12–25% of MC diamniotic twins are complicated by selective intrauterine growth restriction (sIUGR) . Twin oligohydramnios-polyhydramnios sequence (TOPS), twin anemia-polycythemia sequence (TAPS) and major discordant structural anomalies are reported in 10%, 6% and 6% of MC twins, respectively . Umbilical cord occlusion is the most frequently used method for the selective termination of MC multifetal gestations, with lethal anomalies in the co-twin.
As there is little data concerning the placental examination with dye injection in the case of fetal demise of the co-twin after selective termination, we aimed to investigate placental angioarchitecture. Here, we present a case of sudden fetal demise of a co-twin after selective termination using laser coagulation, probably due to donor-recipient artery-vein anastomoses.
A 29-year-old gravida-2-para-1 at 19 weeks’ gestation was referred to our department for TOPS. Her physical and gynecological examination were normal. The fetal examination revealed a diamniotic MC twin pregnancy with concordant fetal growth. Estimated fetal weights were appropriate for gestational age. The recipient twin was diagnosed with polyhydramnios and the donor twin was diagnosed with hydrocephalus and oligohydramnios. The diagnosis of TOPS stage 1 was made on the basis of the Quintero staging system. The deepest vertical pocket was 87 mm for the recipient and 12 mm for the donor twin. Evaluation of the intracranial anatomy of the donor twin revealed bilateral ventriculomegaly (Figure 1). Cisterna magna and cerebellar hemispheres were normal in the transcerebelllar plane. There was no evidence of posterior fossa anomaly in the donor twin. Complications of TOPS and prognosis of discordant anomaly and risks of intrafetal laser surgery were discussed with the family and the patient opted for intrafetal surgery. The operation was performed as follows: after skin disinfection, cutaneous and subcutaneous infiltration of a local anesthetic were done. Thereafter, an 18 G needle (Cook Medical , Brisbane, Queensland, Australia) was inserted into the amniotic cavity of the donor twin under ultrasound guidance and 20 mL of the amniotic fluid sample was obtained for prenatal cytogenetic evaluation. The needle was directed and inserted toward the fetal pelvic region of the donor twin without contacting umblical vessels, and a laser fiber (0.4 mm) was inserted through the needle until it was seen protruding 5 mm beyond the needle tip near the iliac arteries. The vessels were coagulated until no color flow was seen. No bleeding complications were observed and cessation of umbilical blood flow was seen. After the procedure, the fetal heart rate of the recipient twin was checked and fetal bradycardia of 80 rpm prolonged for 6 h was observed. No bleeding or sign of preterm premature rupture of membranes (PPROM) were observed. At the sixth hour of the operation, examination revealed fetal demise of the recipient twin. The patient underwent induction of abortion. The placenta was examined with green-yellow-blue and white dyes after abortion (Figure 2). After detailed examination of the placenta, we determined 13 major venous vessels on the side of the recipient twin. Of these 13 vessels, eight had arterial pairs (black circle); however, five venous vessels had arterial flow from donor fetus 2 (red circle), which is arteriovenous anastomosis. We observed one superficial end-to-end arteriovenous anastomosis from recipient to donor, which is diagnosed by direct communication with dye transition (blue circle).
Selective termination has been demonstrated to be an effective procedure against TOPS, sIUGR, twin reversed arterial perfusion (TRAP) sequence in the case of an anomalous MC co-twin. Several methods such as intrafetal laser, fetoscopic-directed cord ligation, bipolar electrocoagulation, harmonic scalpel cord coagulation, thermal coagulation, laser coagulation and radiofrequency ablation have been described in the literature . Laser could be used either for obliterating placental anastomoses or umbilical cord coagulation in selective reduction . Regardless of which surgical technique is performed, a recent review showed survival rates of 82%, 85% and 75% for the remaining twin in TTTS, severe malformations and TRAP sequence, respectively . Despite reducing maternal-fetal mortality, these procedures carry a risk of fetal loss, PPROM and preterm delivery . PPROM is the most common complication of umbilical cord occlusion techniques . Fetal death of the co-twin, preterm labor, preterm delivery, intrauterine infection and placental or myometrial bleeding have been also described in the literature . Heavy cord bleeding can be a leading mechanism for early fetal death of the co-twin; however, there are several cases of unexplained fetal demise after selective termination in MC pregnancies in the literature. In our case, there was no bleeding complication. We performed a placental dye examination and observed heavy blood supply from the donor to the recipient fetus. Therefore, in our opinion, cessation of the umblical blood flow in the donor caused severe hypovolemia, which explains the bradycardia in the recipient soon after intrafetal laser intervention. We observed five artery-vein cotyledon anastomoses from the donor to the recipient and one artery-vein direct end-to-end anastomosis from the recipient to the donor. Artery-to-artery and vein-to-vein anastomoses were not seen.
In total, the recipient had 13 veins, of which five veins were supplied by donor arteries. After cessation of the umblical blood flow, the major blood supply was shut down by intrafetal laser surgery. We believe that this was the main reason of bradycardia and fetal demise in the recipient.
Although it is thought that the underlying mechanism is changes in vascular resistance of the demised co-twin leading to acute hypotension or even death of the other twin in MC pregnancies, the exact mechanism for fetal demise of the co-twin after selective termination is unknown. Our hypothesis for this situation is supported by macroscopic evaluation of the placenta with color-dye injection.
In conclusion, there are still many unanswered questions regarding placental physiology after fetoplacental surgery. Future placental examinations and dye-injection studies are needed to understand placental vascular changes after fetoplacental surgery. We have to bear in mind that fetal demise of a co-twin is not a surprise such as in our case.
Conflict of interest: Authors state no conflict of interest.
Material and methods
Informed consent: Informed consent has been obtained from all individuals included in this study.
Ethical approval: The research related to human subject use has complied with all the relevant national regulations, and institutional policies, and is in accordance with the tenets of the Helsinki Declaration, and has been approved by the authors’ institutional review board or equivalent committee.
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