Strengths and Limitations
To our knowledge, this is the first study of outcomes following
detection of oedema in fetuses with CRL between 28 mm and 44 mm in women
requesting cell-free DNA testing for aneuploidy screening.
The main limitations of this study are its retrospective design and the
fact that the database search relied on reported fetal oedema,
potentially underestimating the incidence of this finding by not
including cases where oedema was present but not mentioned in the report
due to poorly defined terms and the assumption by some reporting
physicians that mild oedema may be a normal transient finding in early
gestation. Nevertheless, it is likely that the cases with significant
oedema were captured and the incidence seems reasonable. Additionally,
fetal oedema in early pregnancy is rare and the number of cases with
fetal hydrops was small, but the higher incidence of poor outcomes in
the more severe cases is biologically plausible.
The lack of standardized definition for early fetal oedema and
differentiation between cystic hygroma and increased nuchal translucency
has been highlighted in various studies resulting in inconsistent
reporting of outcomes.6 The authors refrained from
using the term cystic hygroma to describe nuchal oedema as frequently
with the high resolution of the ultrasound probes fine septations are
seen in cases with increased nuchal translucency. Additionally, the
presence of fine septations as an independent risk factor for
chromosomal anomalies is not well established.7