Interpretation
The lower than expected number of cases reflects the decrease seen in
twin pregnancy perinatal mortality reported by MBRRACE-UK in
2013-20162. It is thought this decrease may be a
consequence of improved care for MC twin pregnancies, particularly in
recognising and treating complications unique to MC twins, and
development of new treatment techniques including the Solomon Technique
for FLA26. This is also linked to updated national and
international guidance13, 15, 19 , which if
implemented has been demonstrated, by Twins Trust, to lower adverse
outcome rates27. However the latest MBRRACE-UK report
published in October 2019 reported an increase in the stillbirth and
neonatal death rates in twin pregnancies in 201722. It
is important to consider data over a longer period alongside the use of
three year rolling averages to better reflect trends in perinatal
mortality2.
MC twin pregnancies complicated by sIUFD have a high risk of subsequent
co-twin neurologic morbidity. From these data it appears that prenatal
and indeed postnatal screening for abnormalities of the central nervous
system in survivors is not routine in the UK. There is a need to
strengthen professional guidance and practice amongst both obstetricians
and neonatal paediatricians19.
This study strengthens the argument made in our 2019 systematic review
and meta-analysis for the need for a purposely designed prospective
study, ideally with antenatal and postnatal imaging and long-term
follow-up 7.
There is no specific guidance regarding when and how co-twins after
sIUFD should be delivered. Of note in this study there was a high rate
of preterm birth (both spontaneous and iatrogenic) and a high rate of
emergency caesarean sections. The majority of co-twin survivors were
admitted to the neonatal unit with prematurity the commonest indication.
Despite the high risk nature of the pregnancy and requirement for
admission to NNU, very few babies had planned follow-up despite an
association with adverse long-term outcomes10.
The uptake of post-mortem examination was low (25.4%) for the initial
sIUFD but increased to 40% if the co-twin died as well. This is below
the 75% recommended uptake by the RCOG28, and may
reflect that parents accept that MC twin pregnancies are higher risk,
and even if a cause was not apparent antenatally, the findings of the
post-mortem are unlikely to affect a subsequent pregnancy as it may be
linked to monochorionicity. Despite post-mortem being considered the
most useful investigation for parents to find out why their baby
died29, in 6/9 post-mortems in which the UKOSS
reporter knew the findings, the post-mortem was inconclusive. This
highlights another area of future research, as there is not currently a
specific classification system for cause of death in MC twins, which is
often different to the cause of death in singletons, and is the
classification system which pathologists have to currently use. Since
performing this study, we have proposed a new classification system of
causes of death in twin pregnancies (CoDiT) which requires further
validation30. These findings also raise the
consideration of whether specialist perinatal pathologists are needed
for MC twin pregnancy post-mortems, and whether injection studies should
be performed in all MC twin pregnancies to aid determining cause of
death.