This study evaluated the incidence and consequences of misdiagnosed twin-twin transfusion syndrome (TTTS). The researchers found that in 33.1% of TTTS cases treated with laser surgery, the chorionicity was incorrectly identified or TTTS was misdiagnosed prior to referral. Cases of misdiagnosed TTTS were referred later in pregnancy at a more advanced stage of disease. This resulted in worse maternal and neonatal outcomes including higher rates of preterm birth and neonatal death. The study emphasizes the importance of accurate identification of chorionicity in early pregnancy scans and close monitoring of monochorionic twin pregnancies to enable early diagnosis and treatment of TTTS.

1. UOG Journal Club: August 2014
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important
consequences
D. Baud, R. Windrim, T. Van Mieghem, J. Keunen,
G. Seaward and G. Ryan
Volume 44, Issue 2, Date: August 2014
Journal Club slides prepared by Dr Aly Youssef
(UOG Editor for Trainees)

2. Introduction
• Twin–twin transfusion syndrome (TTTS) is a serious complication
affecting about 15% of monochorionic (MC) twin pregnancies.
• Diagnosis relies on accurate determination of chorionicity at 11–14 wks
and demonstration of polyhydramnios in a recipient twin and
oligohydramnios in a donor.
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014
T-sign
(monochorionic)
Lambda-sign
(dichorionic)

3. Introduction
• If TTTS goes unrecognized, perinatal loss is >90%, with a high risk
of neurologic impairment in survivors and severe maternal
complications.
• Early recognition of this disease and referral of patients for therapy
is mandatory to improve pregnancy outcome.
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014

4. To evaluate the incidence and
consequences of ‘misdiagnosed’ TTTS.
Objective
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014

5. • A retrospective review of chorionicity ascertainment and referral
diagnoses in 323 consecutive pregnancies with TTTS, treated
with fetoscopic laser ablation of placental anastomoses at Mount
Sinai Hospital, Toronto, from January 1999 to April 2012.
• Failure to identify monochorionicity and/or to diagnose TTTS
before referral were considered as ‘misdiagnosed’ cases.
• Patient demographics, TTTS stage, perioperative characteristics,
complications and maternal and neonatal outcomes of
‘misdiagnosed’ TTTS cases were compared with cases in which
chorionicity and TTTS were correctly diagnosed.
Methods

6. Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014
• Among 323 consecutive patients requiring laser for TTTS, 107
(33.1%) were referred with either an incorrect diagnosis of
chorionicity (n = 95, 88.8% of ‘misdiagnosed’ cases) and/or a
diagnosis other than TTTS (n = 23, 21.5% of ‘misdiagnosed’ cases).
• In 37 (11.5%) patients, chorionicity was not mentioned on any
ultrasound report.
• An early ultrasound was not carried out in 19 of these cases.
• It was performed but did not assess chorionicity in the other 18.
Results

7. TTTS with correct diagnosis
(n = 216)
Misdiagnosed TTTS cases
(n = 107)
P
Stage
Stage I
Stage II
Stage III
Stage IV
4.6%
36.1%
51.4%
7.9%
2.8%
25.2%
55.1%
16.8%
0.037
Gestational age
at laser (wks)
20.1±0.2 20.9±0.3 0.018
Length of
surgery (min)
55±2 62±3 0.04
Preterm labor
<32 weeks
<28 weeks
44.4
22.2
57.9
33.6
0.022
0.031
Results
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014

8. TTTS with correct diagnosis
(n = 216)
Misdiagnosed TTTS cases
(n = 107)
P
Dual survival (%) 61.1 50.5 0.068
Donor survival (%) 70.4 61.7 0.131
Recipient survival (%) 78.2 75.7 0.672
Donor weight at
delivery (g)
1451±55 1218±78 0.01
Recipient weight at
delivery (g)
1714±53 1550±76 0.04
Neonatal death <7
days after birth
6.0 19.6 < 0.001
Neonatal death <28
days after birth
6.5 20.6 < 0.001
Results: Neonatal survival and outcome
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014

9. • In referred women, chorionicity and/or TTTS were incorrectly
diagnosed in one third of cases.
• These patients were referred later and at a more advanced stage of
disease, resulting in worse maternal and neonatal outcomes.
• These findings underline the importance of:
I. Correctly identifying chorionicity at the 11–14-week ultrasound scan.
II. Following all monochorionic pregnancies with an ultrasound scan
every 2 weeks, looking specifically for any evidence of TTTS.
Discussion
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014

10. Strengths
• Comprehensive and clinically important outcomes.
• Large sample size.
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014
Limitations
• Retrospective design (although infant outcomes and
pregnancy complications were gathered prospectively as
part of quality insurance program).
• Data were only derived from pregnancies that underwent
fetoscopic laser ablation, which might underestimate the
true rate of ‘misdiagnosed’ patients.

11. Discussion points
• What is the rate of misdiagnosed chorionicity and/or TTTS
in your unit?
• What national policies should be endorsed in order to
improve early prenatal detection of chorionicity and/or
TTTS?
• Should all monochorionic twin pregnancies be followed up
by referral centers?
• Should a first-trimester scan of twin pregnancy be
performed exclusively by expert operators with formal
training on twin scanning?
Twin–twin transfusion syndrome:
a frequently missed diagnosis with important consequences
Baud et al., UOG 2014