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