Strengths and limitations
To the authors’ knowledge, this is the first UK-wide study of sIUFD in
MC twin pregnancies. A major strength of this study is that data were
collected from UK centres, thus the results represent current UK-wide
practice. UKOSS is a validated mechanism of collecting data on
relatively rare conditions that is UK wide. Data collection relies on a
system of designated clinician data collectors. In this study there were
8 cases for whom outcome data was missing following fetal therapy at a
tertiary centre. This is in contrast to the only other UKOSS study
relating to a fetal condition, gastroschisis, where there were no
missing outcome data. This difference might reflect the complexity of
complicated MC twins requiring management at multiple care providers
(supraregional, regional and local), and that within the gastroschisis
study outcome data was also collected via paediatric surgeons and via
cross-checking with congenital anomaly registers. One of the
difficulties of data collection in complex conditions is a lack of
standard pathways of care and definitions of outcomes (e.g. ultrasound
findings). This is especially true for the complex conditions
complicating MC pregnancies, where each fetus maybe affected
differently. Since data collection for this study there have been
initiatives to guide the management of these complex pregnancies, and
define outcomes 19, 20and within the UK specialist
fetal medicine commissioning will improve pathways of care.
The number of cases notified was considerably lower than our pre-study
estimate. However, MBRRACE-UK data (national surveillance of perinatal
deaths) in 2016, noted perinatal mortality rates amongst twins as the
lowest ever reported21, 22 and thus we employed
triangulation of data with MBRACCE-UK to check case ascertainment. Using
ONS data23 and MBRACCE data21, and
newer evidence to suggest that 20% of twins are
monochorionic24, 25 (as opposed to the 30% of our
original estimate), we calculated incidence of single twin demise across
the 2 years of our study. This gives very similar figures of an
estimated 75 cases in 2016 and 84 in 2017 with incidence of 37.6-38.7
per 1000 monochorionic maternities. A further strength of this study was
the collection of data relating to interventions, management and
outcomes for both mother and neonate. It is not possible to collect data
for the baby via the UKOSS system past the point of discharge from
hospital after birth. Further studies and research in this area should
include data related to longer term outcomes for the
baby7.