DOI: 10.1111/j.1471-0528.2007.01336.x
Fetal medicine
www.blackwellpublishing.com/bjog
Severe twin–twin transfusion syndrome:
outcome after fetoscopic laser ablation of
the placental vascular equator
AM Ierullo, AT Papageorghiou, A Bhide, N Fratelli, B Thilaganathan
Fetal Medicine Unit, Department of Obstetrics and Gynaecology, St George’s Hospital NHS Trust, London, UK
Correspondence: Dr B Thilaganathan, Fetal Medicine Unit, Department of Obstetrics and Gynaecology, 4th Floor, Lanesborough Wing,
St George’s Hospital NHS Trust, Blackshaw Road, London SW17 0QT, UK. Email basky@pobox.com
Accepted 3 January 2007.
Setting Tertiary referral fetal medicine unit.
average, four vessels were ablated during each procedure, with
a mean operative time of 15 (range 5–25) minutes. None of
the women required a repeat fetoscopic laser treatment for
recurrence of the TTTS. There was at least one survivor in 74%
(57/77) of pregnancies, and the overall survival rate was
57% (88/154).
Population Women with pregnancies complicated by severe TTTS
Conclusions Fetoscopic laser ablation is a safe and effective form
(Quintero stage III or IV), before 26 weeks of gestation.
of treatment in the management of severe TTTS. The technique of
identifying the common villous district of the placenta by
ultrasound and photocoagulating any vessels crossing the vascular
equator appears to be an acceptable alternative to both the
nonselective and highly selective methods described so far. This
approach is associated with a short operating time, low likelihood
of TTTS recurrence or fetal anaemia and with survival results that
are equivalent to previously reported techniques.
Objective To assess the safety and efficacy of a modified fetoscopic
laser ablation technique for the management of severe twin–twin
transfusion syndrome (TTTS) in a large series of pregnancies.
Design Prospective cohort study.
Methods Fetoscopic laser ablation of placental anastomoses was
performed. The sonoendoscopic approach was used to identify the
placental vascular equator and to photocoagulate crossing vessels.
Main outcome measures Overall survival, fetal and perinatal
mortalities, gestational age at delivery, birthweight, operating time
and recurrence of TTTS.
Results A total of 77 women underwent the procedure. The mean
gestational age at treatment was 20 (range 16–26) weeks. On
Keywords Fetoscopy, laser ablation, monochorionic, twins, TTTS.
Please cite this paper as: Ierullo A, Papageorghiou A, Bhide A, Fratelli N, Thilaganathan B. Severe twin–twin transfusion syndrome: outcome after fetoscopic laser
ablation of the placental vascular equator. BJOG 2007;114:689–693.
Introduction
Twin-to-twin transfusion syndrome (TTTS) is a recognised
midtrimester complication occurring in up to 15% of monochorionic gestations.1 If left untreated, the mortality of this
condition exceeds 90%, with significant neurological morbidity in 30–50% of surviving twins.2,3 The most well established
treatment options for TTTS include serial amnioreduction
and fetoscopic laser ablation of the placental vascular anastomoses. The reported survival rates for amnioreduction are
39–64% compared with 56–62% for fetoscopic laser ablation.4–7 Long-term neurodevelopmental morbidity rates for
amnioreduction are 7–26%3,8–12 compared with 6–11% for
laser ablation.13–15 In 2005, a systematic review confirmed
the significant increase in survival rates and reduction in
neurological morbidity with the use of laser ablation compared with amnioreduction in severe TTTS.16 However, laser
ablation is a more complex technique and less readily available than amnioreduction.
In the nonselective fetoscopic laser technique, all vessels
crossing the intertwin membrane are photocoagulated.4 This
approach is thought to be associated with higher fetal loss
rates than the highly selective technique, where all vessels are
followed systematically from the point they cross the intertwin membrane until it can be verified whether they are
normal or resulting in an anastomoses with the co-twin.17
Although the highly selective technique may have a higher
survival rate, it is a time-consuming operation, with an
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689
Ierullo et al.
average operating time of 73 minutes (range 20–178 minutes).17
We previously described an alternative, simpler, faster technique for undertaking selective laser ablation using preoperative ultrasound identification of the placental common villous
district and vascular equator of the placenta by determining
the umbilical cord placental insertion sites.18 The aim of this
study was to evaluate the use of the placental vascular equator
technique for fetoscopic laser ablation in severe TTTS.
Methods
Between January 2002 and March 2006, fetoscopic laser
coagulation was carried out in 77 pregnancies complicated
by severe TTTS (Quintero stage III or IV).19 In all cases, firsttrimester ultrasound established monochorionicity by showing a single placental mass and the absence of the lambda
sign of the intertwin membrane.20 All pregnancies showed
characteristic ultrasound features of TTTS: polyhydramnios
(deepest vertical pool of ‡8 cm) and a distended bladder in
the recipient, and oligohydramnios (deepest vertical pool
of £1 cm) and a collapsed bladder in the donor. The Quintero staging system was used to describe the severity of the
TTTS.19
Women were counselled regarding the possible outcomes
of the available options, including expectant management,
amnioreduction and fetoscopic laser coagulation.
Preoperative ultrasound assessment
Prior to the procedure, ultrasound was used to visualise the
placental site, the donor and recipient umbilical cord placental insertions and to identify the common villous district
of the placenta, as previously described.18 In short, the common villous district was estimated to run midway and perpendicular to an imaginary line running between the donor
and recipient cord placental insertion sites.18 The anatomical
relationship of the cord insertions and common villous district described above are well established.21 In 2005, this anatomical relationship was used to accurately describe placental
territories in a placental morphology study after fetoscopic
laser ablation.22 The marginal cord insertions seen in the
majority of TTTS pregnancies mean that the common villous
district is usually eccentrically positioned, with a smaller placental territory for the donor. The placental disc, cord insertions and vascular equator were then marked on the maternal
abdomen to help determine the site of fetoscope entry and to
shorten operating times.
Operative procedure
The fetoscope entry site was chosen in order to enter the
recipient sac on the opposite side of the uterus to the placenta
without injury to the mother or the fetuses. Local anaesthesia
(1% lignocaine) was injected from skin to myometrium,
690
and intravenous antibiotic prophylaxis (cefuroxime 750 mg)
and intravenous maternal sedation (5–10 mg diazepam as
required) were given perioperatively. A rigid 2-mm-diameter 0°
fetoscope in a 2.8-mm operating sheath (Olympus Keymed,
Southend-on-Sea, UK) was introduced into the recipient sac
under continuous ultrasound guidance. A 400-mm-diameter
laser fibre (KTP/Nd:YAG Laserscope; Gwent, UK) was passed
down the operating channel until the tip was just visible
through the fetoscope. When the placenta was positioned anteriorly, a lateral fetoscope insertion in the maternal flank was
used, and the maternal abdomen was depressed manually to
bring the equatorial region into view.
Ultrasound guidance was used to bring the fetoscope tip
close to the common villous district previously marked on the
maternal abdomen. Once the placenta was visible fetoscopically, the rest of the procedure was conducted under direct
vision. Transabdominal ultrasound was used to guide the tip
of the fetoscope along the predrawn line on the abdomen, and
fetoscopy was used to visualise the vessels directly. The fetoscope was always orientated using a ‘cardinal’ point system:
north (donor cord insertion) and south (recipient cord insertion). The fetoscope was then moved along the ultrasonographically determined common villous district (traversing
the placenta in an east–west orientation) to visualise any
vessels crossing the placental equator. All vessels judged to
cross the vascular equator were coagulated using a pulsed
laser with an output of 30–60 watts in 3-second bursts. In
the vast majority of cases, the vessels seen in the common
villous district were not paired by another vessel from the
same fetus. Such single, unpaired vessels were always photocoagulated. On rare occasions, paired vessels from the same
twin were seen in the common villous district. These were
ablated whenever vessels from the co-twin were visible in
close proximity in order to ensure that there were no persistent postoperative intertwin vascular connections.
At the end of the procedure, amniotic fluid was drained
until the amniotic fluid index in the recipient normalised. A
40-ml recipient amniotic fluid sample was always sent for fetal
karyotyping. In order to reduce the risks for preterm delivery,
tocolytic therapy (glyceryl trinitrate patch 5 mg) was administered for 24 hours. The women were discharged from the
hospital from 8 hours postoperatively, and serial follow-up
appointments to check the effects of therapy were scheduled
for 2 and 8 weeks later.
Outcome variables
The outcomes measured included the severity of the TTTS at
presentation, operative details (gestation, operative time from
fetoscope insertion to removal, laser power used and amount
of fluid drained), delivery details (gestation and birthweight)
and perinatal outcome (spontaneous miscarriage, medical
termination, intrauterine death, neonatal death and infant
survival). Outcome measures were evaluated on the basis of
ª 2007 The Authors Journal compilation ª RCOG 2007 BJOG An International Journal of Obstetrics and Gynaecology
Laser ablation of the placental equator in TTTS
the number of pregnancies or the number of fetuses or
infants, as appropriate.
Table 2. Obstetric outcomes with details of survival (%), gestational
age range at delivery (%) and birthweight (median and range)
Statistical analysis
No. of pregnancies (%)
Continuous variables were reported as medians (±range). In
the analysis of the time to delivery, data were censored at the
time of the termination of pregnancy.
Results
Seventy-seven monochorionic twin pregnancies were diagnosed with severe TTTS and underwent fetoscopic laser ablation during the study period. All cases were diagnosed as
either Quintero stage III (n = 68) or stage IV (n = 9). The
cord insertion was noted to be marginal in 67 (87%) donors
and central in 61 (79%) recipients. The operative details are
shown in Table 1. An average of four (range 1–11) vessels were
photocoagulated intraoperatively. The delivery details and
perinatal outcomes are shown in Tables 2 and 3. The median
interval between treatment and delivery in all pregnancies,
including miscarriages, was 9 weeks (interquartile range 3–
13 weeks). There was at least one surviving infant in 74%
(95% CI: 63–83%) of the pregnancies treated. The overall fetal
survival rate was 57% (88/154, 42 donors and 46 recipients).
There were five spontaneous miscarriages within 7 days
of the procedure (Table 3, ten fetal losses). In a further six
pregnancies (seven fetuses), the parents requested medical
termination of pregnancy because of the death of one twin
(n = 3) or the diagnosis of cerebral haemorrhage (n = 4). In
the latter four cases, the diagnosis was made immediately after
the procedure because amniodrainage significantly improved
ultrasound visualisation.
There was no evidence of a recurrence/persistence of TTTS
or fetal anaemia evident on ultrasound monitoring in the
continuing pregnancies. Repeat fetoscopic laser ablation,
amniodrainage or fetal intravascular transfusion was not
required prior to delivery in any of the cases.
Discussion
The aim of fetoscopic laser ablation for treatment of TTTS is
to interrupt the abnormal placental vascular communicaTable 1. Operative outcomes with details of gestational age at
treatment, operating time from fetoscope entry to exit, amount of
laser energy used for the ablation and quantity of amniotic fluid
drained at the end of the procedure
Survival, n
0 survivors
At least one survivor
One survivor
Two survivors
Gestational age at delivery (weeks)
,24
24 to ,28
28 to ,32
32–37
Birthweight (g)
Recipient
Donor
20 (16–26)
15 (5–25)
2526 (469–9254)
1000 (200–7000)
16 (21)
14 (18)
7 (9)
40 (52)
Median (range)
2016 (565–3519)
1539 (436–2752)
tions, which are assumed to be the underlying mechanism
of the syndrome.23 Although the most recent randomised trial
proposes that fetoscopic ablation should be undertaken
regardless of the severity of TTTS,5 a systematic review of
TTTS treatment suggests that fetoscopic intervention may
not be justified in less severe (stages I and II) TTTS cases.16
Furthermore, it is difficult to be certain of the diagnosis of
TTTS with stage I (amniotic fluid discordance) and stage II
(absent bladder in the presumed donor), as these ultrasound
signs may be seen transiently in a normal twin pregnancy.
This study provides information on outcome after selective
fetoscopic laser ablation for severe (stages III and IV) TTTS.
Pregnancy outcome after fetoscopic laser ablation
The survival rate of at least one baby per pregnancy for severe
TTTS in this study was 74% (95% CI 63–83%). About onethird of pregnancies deliver very prematurely before 28 weeks
of gestation (Table 2). Of the 16 pregnancy losses before 24
weeks of gestation, it should be noted that six pregnancies
(seven fetuses) were medically terminated either because
pre-existing cerebral haemorrhage became evident immediately after amniodrainage at fetoscopic laser treatment or at
the parents request after co-twin death (Table 3). There have
Table 3. Fetal and perinatal mortalities, expressed as number of
fetuses and percentage of 154 fetuses overall
n (%)
Median (range)
Gestational age (weeks)
Operating time (minutes)
Laser power (joules)
Amniotic fluid drained (ml)
20 (26)
57 (74)
26 (34)
31 (40)
Termination
Miscarriage
Intrauterine death
Neonatal death
ª 2007 The Authors Journal compilation ª RCOG 2007 BJOG An International Journal of Obstetrics and Gynaecology
7 (5)
10 (6)
39 (25)
10 (6)
691
Ierullo et al.
been numerous small reports on the success or survival rates
after fetoscopic laser ablation.5–7,17,24–26 However, most of
these studies have been too small to quote specific survival
rates for severe TTTS, and the cases are mixed with regards to
whether a selective or nonselective approach was used. Only
two previous multicentre studies reported on stage-based (III
and IV) survival rates for severe TTTS: Senat et al.5 quoted
a 66% (95% CI 48–81%) survival using the nonselective
technique in 35 pregnancies. Quintero et al.17 reported a
79% (95% CI 64–91%) survival rate (including terminations)
using the selective technique in 74 pregnancies. These rates
compare very favourably with the survival rate of 74% from
77 pregnancies in this single-centre study.
Equatorial, highly selective and nonselective
fetoscopic techniques
The equatorial technique described here for performing selective laser ablation made it possible to perform all procedures
under local anaesthesia and led to a short median fetoscopy
time of 15 minutes (range 5–25 minutes). The shorter fetoscopy times were achieved in cases with a posterior placenta
where both cord insertions were marginal resulting in only
one or two anastomoses in the vascular equator. Such anastomoses required only 6 to 9 seconds of laser energy and
repeat visualisation 1 to 2 minutes later to ensure that recanalisation had not occurred. This should be compared with the
use of general anaesthesia and mean operating time of 72
minutes (range 20–178 minutes) from the only previous
report of highly selective laser photocoagulation to state the
length of the procedures.17 Although it is not possible to relate
shorter operating times and the selective technique to improved pregnancy outcomes directly, the avoidance of general
anaesthesia and associated complications in a gravid woman
are clearly advantageous.
The donor cord insertion is marginal in the majority of
TTTS cases, thereby locating the placental equator eccentrically with approximately 30–40% of the placental territory
belonging to the donor. The survival of 42 donors and 46
recipient twins in the current cohort indicates that significantly increased losses in donor twins are not seen with the
equatorial technique. The nonselective technique uses the
intertwin dividing membrane as an anatomical landmark,
and all vessels traversing the membrane are photocoagulated.4
However, as a consequence of the increased amniotic fluid
volume in the recipient sac, the dividing membrane is pushed
towards the donor fetus. Using the intertwin membrane as an
anatomical landmark may well reduce operating times but
increases the likelihood of excessive destruction of the donor
placental territory.
In 2000, a highly selective coagulation technique was
described, where only the vessels involved in intertwin blood
transfusion are photocoagulated.17 In the selective technique,
a lengthy fetoscopic survey of placental surface vessels is
692
undertaken to identify the vascular communications between
the donor and the recipient twin. In a study comparing the
two techniques, selective laser photocoagulation appeared to
be slightly more effective in the treatment of TTTS when
compared with the nonselective technique.17 However, the
cases were not comparable as nonselective laser was undertaken in more severe TTTS cases. Furthermore, the differences in survival were only just significant when one-tailed
Fisher’s exact test was used but not significant with a twotailed test.
Late complications after fetoscopic laser
Apart from intrauterine death and miscarriage, late fetal
complications after fetoscopic laser treatment have been
described.17,26–29 The most common of these are recurrence
of TTTS, reversal of TTTS and fetal anaemia after intrauterine
death of the co-twin, all as a consequence of persistent or
recanalised intertwin vascular connections. The best estimates
of the incidence of these complications are provided in a
study of 151 cases of TTTS treated by selective fetoscopic
laser therapy.30 The study showed a recurrence of TTTS
in 14% of cases and fetal anaemia severe enough to require
transfusion in 13%.30 The were managed by repeat fetoscopic
laser, intrauterine blood transfusion or delivery.30 In the current single-centre cohort, none of the continuing cases
showed recurrence of TTTS or fetal anaemia after co-twin
death. Although the simpler and faster equatorial technique
may not result in improved survival rates, it would be
appropriate to speculate that it results in a more effective
separation of the fetal circulations, thereby preventing these
late complications.
Conclusion
Fetoscopic laser ablation is a safe and effective form of treatment in the management of severe TTTS with significant
advantages over aggressive serial amniodrainage. We describe
an alternative technique to the nonselective and highly selective
approaches used so far, where the common villous district of
the placenta is identified by ultrasound and the vessels crossing this vascular equator are identified and photocoagulated
fetoscopically. This approach is associated with a short operating time, with avoidance of general anaesthesia, with low late
postoperative complications and with survival results that are
at least as promising as previously reported techniques. j
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