Objective
We sought to assess the efficacy, complication rates, and outcomes for complex monochorionic pregnancies undergoing selective fetal reduction using radiofrequency ablation (RFA).
Study Design
In this prospective observational study, 100 consecutive cases of selective fetal reduction using RFA were analyzed. All cases were managed at the Centre for Fetal Care at Queen Charlotte’s and Chelsea Hospital in London. Indications for offering RFA, details of the procedure, and pregnancy outcomes were collected and analyzed.
Results
The main indications for RFA were discordant fetal anomaly and twin-twin transfusion syndrome. Overall live birth rate was 78% and the median gestation at delivery was 35.15 weeks. Delivery <32 weeks’ gestation occurred in 17.9% of cases. Postprocedure abnormal antenatal magnetic resonance imaging occurred in 3% of cases. There was no statistical difference in outcomes with regard to gestation when the procedure was performed or the indication for the RFA.
Conclusion
RFA appears to be a reasonable option for selective fetal reduction in complex monochorionic pregnancies with an overall survival rate of 78%.
The presence of placental vascular anastomoses confers unique challenges to selective fetal reduction in monochorionic pregnancies, primarily as a consequence of these anastomoses that allow an acute unidirectional interfetal transfusion when 1 twin dies in utero. This mechanism is believed to cause cerebral injury (multicystic encephalomalacia, germinal matrix or parenchymal hemorrhage or gray-matter lesions) to a surviving co-twin when it experiences acute severe hypotension during the agonal event in the dying twin. The monochorionic angioarchitecture therefore requires ablation of blood flow in the umbilical cord during selective fetal reduction to prevent acute intrafetal transfusion. Currently the 2 most commonly used techniques for selective reduction are bipolar cord occlusion, and more recently, radiofrequency ablation (RFA). RFA involves generating changes in alternating current at very high frequencies (200-1200 KHz) between the tines of the needle. As the electrical current alternates in various directions between the tines, tissue ions become agitated as they attempt to align with the electrical field. Frictional heat is then produced resulting in very high tissue temperature, which causes tissue coagulation and necrosis.
In experienced hands, both techniques are effective and can achieve complete ablation of blood flow in the targeted fetus. However, the initial enthusiasm for RFA has been tempered by more recent reports suggesting that its application was associated with a decrease in the overall survival rate despite a lower risk of preterm rupture of membranes and preterm labor when compared with bipolar cord occlusion. The purpose of this study was to ascertain the perinatal outcomes and procedure-related complications following the use of RFA for a variety of indications in complicated monochorionic pregnancies. To our knowledge this is the largest case series of this procedure to date.
Materials and Methods
This was a prospective study of 100 consecutive cases of monochorionic pregnancies that underwent selective reduction using RFA from January 2008 through September 2012. Some of the cases included in this series have been previously reported in 2 other publications from our unit. All patients were seen at the Centre for Fetal Care at Queen Charlotte’s and Chelsea Hospital, Imperial College London, which is a tertiary referral center for fetal and maternal medicine. All cases of RFA were performed by 2 experienced interventional fetal medicine specialists (S.K. and R.C.W.).
RFA was performed for a variety of indications (twin-twin transfusion syndrome [TTTS], major structural malformations, severe discordant growth restriction, acardiac fetus with twin reversed arterial perfusion sequence, and multifetal reduction). Although fetoscopic laser treatment was always offered as a therapeutic option for cases of TTTS, not all parents consented to this option. Other factors that influenced their decision to opt for RFA included their desire for multifetal reduction given their multiple pregnancy or situations where fetoscopic laser was more challenging (eg, extensive anterior placenta or triplet pregnancy). Prior to any procedure, detailed ultrasound examination was performed to confirm gestation and chorionicity and to detect the presence of any structural malformations, abnormal growth, or TTTS. Patients were counseled in detail about the risks of the procedure including miscarriage, preterm labor, co-twin demise and neurological or thermal injury to the surviving twin.
Technique
RFA was performed as a day case procedure. After informed consent, the procedure was performed under local anesthesia under antibiotic cover. Empirically, all patients received indomethacin (100 mg) rectally and progesterone 400-mg vaginal pessaries for 3 days postprocedure to minimize the risk of procedure-related loss. We used a radiofrequency generator (AngioDynamics-RITA 1500X, AngioDynamics Inc, Latham, NY) and RITA–StarBurst SDE electrosurgical device (AngioDynamics Inc). The radiofrequency needle was 12 cm in length and had an outer diameter of 17 gauge (4.5F) yielding a spherical area of ablation of 2 cm through the deployment of 3 tines.
Under continuous ultrasound guidance and local anesthetic (1% lignocaine) the radiofrequency needle was inserted percutaneous through a small stab incision into the intrafetal portion of the umbilical cord taking care wherever possible to avoid the placenta. The needle tip position was confirmed by color-flow mapping, before the tines were deployed. Radiofrequency energy was applied by the generator until an average temperature of 110°C was achieved in all the 3 tines for 3 minutes. This constituted a complete cycle. This particular temperature was recommended by the equipment manufacturers. Furthermore, published data support a temperature range of between 110-130°C to achieve vascular occlusion. A cool-down period of 1 minute followed each cycle of heating. If there was discordant heating of the tines, the cycle was stopped and the tines were retracted back into the needle before the needle was repositioned, the tines redeployed and a new cycle commenced. Thermal energy was applied until cessation of blood flow was demonstrated in the umbilical cord by pulsed-wave and color-flow Doppler. In most cases the entire procedure lasted <15 minutes. In some cases, particularly at later gestations when the umbilical cord was thicker with more flow, 2-3 cycles were required before complete cessation of flow was confirmed. Cardiac asystole in the targeted twin was confirmed either immediately or 30 minutes postprocedure if cardiac pulsations were still present at the end of the procedure as asystole did not always immediately occur. However, asystole was confirmed in all cases by 30 minutes following ablation. All patients were discharged the same day. Middle cerebral artery peak systolic velocity measurements of the surviving twin were obtained within 24 hours wherever possible to assess for any evidence of anemia, which might indicate an increased risk of hypotension and cerebral injury. Postprocedure ultrasound was performed in the majority of cases 24 hours following the procedure. In all these cases, the middle cerebral arterial Doppler velocimetry was normal. It was not possible to perform follow-up ultrasound (within 24 hours) in all cases because some patients elected to travel back to their local destination the same day of the procedure.
Following the procedure, all patients were discharged back to their local hospital for follow-up. In the absence of any maternal and fetal indications timing and mode of delivery was left to the discretion of the referring obstetrician. Magnetic resonance imaging (MRI) of the surviving fetus/fetuses in all cases was performed at 22-24 weeks if the initial procedure was done <20 weeks or after a minimum of 4 weeks if the procedure was done >20 weeks’ gestation to detect any evidence of transfusion-related injury that might have occurred as a consequence of the procedure. Statistical analysis was performed using software (SPSS, version 9; IBM Corp, Armonk, NY).
This study was conducted as part of clinical audit of practice, and as such was considered exempt from institutional review board consideration.
Results
Over the study period, 100 procedures were performed (77 in twins and 23 in triplets). The demographics of the study cohort and the various indications for the procedure are detailed in Table 1 . Of the 100 cases 72% (72/100) were monochorionic diamniotic twins, 5% (5/100) were monochorionic monoamniotic twins, 18% (18/100) were dichorionic triamniotic triplets, and 5% (5/100) were monochorionic triamniotic triplets. The leading indication for the procedure was discordant fetal anomaly in 38% (38/100) of cases followed by TTTS in 28% (28/100) of cases (stage 1 [3 cases], stage 2 [9 cases], stage 3 [11 cases], stage 4 [5 cases]). The median gestational age at procedure was 18.0 weeks (range, 12.1–27.6 weeks). The procedure was technically successful in all the cases. In all cases only 1 uterine entry with the radiofrequency needle was required. In some cases, amnioinfusion through the RFA needle was required to improve access to the targeted fetus. No serious (sepsis, hemorrhage, admission to intensive care, maternal death) maternal complications occurred.
| Demographics | Value |
|---|---|
| Age, y | 30.8 (20-42) |
| Ethnicity | |
| Caucasian | 88.0% (88/100) |
| Asian | 11.0% (11/100) |
| African | 1.0% (1/100) |
| Conception | |
| IVF | 31.0% (31/100) |
| Spontaneous | 33.0% (33/100) |
| Missing data | 36.0% (36/100) |
| Pregnancy | |
| MCDA | 72.0% (72/100) |
| MCMA | 5.0% (5/100) |
| DCTA | 18.0% (18/100) |
| MCTA | 5.0% (5/100) |
| Indication | |
| Anomaly | 38.0% (38/100) |
| FGR | 8.0% (8/100) |
| MFPR | 14.0% (14/100) |
| TRAP | 12.0% (12/100) |
| TTTS | 28.0% (28/100) |
| GA at procedure, wk | 17.96 (12.14–27.57) |
| GA at delivery, live birth, wk | 35.15 (24–41) |
Table 2 details the obstetric outcomes for the study cohort. The percentage of women with at least 1 live birth was 78% (78/100). The median gestational age at delivery was 35.2 weeks (range, 24–41 weeks) with a median birthweight of 2494 g (range, 694–4480 g). Of the 6 women (6%) who miscarried (<24 weeks), 50% (3/6) miscarried within 2 weeks of the procedure. The preterm delivery rates were 26.9% (21/78) for <34 weeks and 6.4% (5/78) for <28 weeks ( Table 2 ). Table 3 details the outcomes following the gestation when the procedure was performed. Survival analysis ( Figure ) of cases that underwent RFA at <20 weeks compared with those done >20 weeks’ gestation did not show significant difference between the 2 groups. There were 12 cases (12%) of co-twin demise and 3 cases (3%) had evidence of cerebral injury on postprocedure MRI. There was no correlation between the indication for RFA and the subsequent development of a cerebral lesion. The abnormalities detected included schizencephaly, bilateral pseudocysts adjacent to the lateral cerebral ventricles, and severe ventriculomegaly, respectively. Two of these fetuses were subsequently terminated. The fetus with bilateral pseudocysts was delivered vaginally at 38 weeks and postnatal MRI confirmed the antenatally detected abnormalities. The live birth, miscarriage, and co-twin demise rates as well as the interval between the procedure and delivery according to the various indications are presented in Table 4 . Table 5 details the outcomes for RFA performed for TTTS vs other indications.
| Variable | Value |
|---|---|
| SVD | 64.0% (64/100) |
| Instrumental | 3.0% (3/100) |
| Emergency LSCS | 17.0% (17/100) |
| Elective LSCS | 16.0% (16/100) |
| Birthweight, g | 2494 (694-4480) |
| Live birth rate | 78.0% (78/100) |
| Overall miscarriage | 6.0% (6/100) |
| Miscarriage within 2/52 of procedure | 50% (3/6) |
| Co-twin demise | 12.0% (12/100) |
| TOP | 4.0% (4/100) |
| Abnormal MRI | 3.0% (3/100) |
| Gestation at delivery, live births, wk | 35.33% (24-41) |
| <28 | 6.4% (5/78) |
| <30 | 14.1% (11/78) |
| <32 | 17.9% (14/78) |
| <34 | 26.9% (21/78) |
| <36 | 38.5% (30/78) |
| GA at procedure, wk | No. cases | Live birth | Co-twin demise | Gestation at delivery, live births, wk | Live birth <32/40 wk |
|---|---|---|---|---|---|
| 12-16 | 32 | 68.8% (22/32) | 15.6% (5/32) | 35.7 (28.0–39.57) | 13.6% (3/22) |
| 16-20 | 41 | 80.5% (33/41) | 12.2% (5/41) | 34.7 (24–41) | 24.2% (8/33) |
| >20 | 27 | 85.2% (23/27) | 7.4% (2/27) | 35.9 (25–41) | 13.0% (3/23) |
| χ 2 P value = | .75 | .66 | .52 | .53 | |
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