Statistical analysis
Categorical variables were expressed as absolute numbers and
percentages, and continues variables were expressed in medians and
interquartile ranges (IQR). Differences in characteristics between the
study groups were examined with chi-square or Fisher’s exact test in
case of categorical variables, and t test or Mann-Whitney U test for
continuous variables depending on the distribution. The agreement
between the two operators regarding classification of the type of oedema
was assessed with analysis of intraclass correlation coefficient (ICC).
The primary outcome of the study was the occurrence of chromosomal
abnormalities. Pregnancy outcomes, karyotype and microarray
abnormalities and ultrasound findings associated with early fetal oedema
are described as proportions within each group.
Finally, the association between oedema thickness with CRL 28 - 44 mm
and the nuchal translucency at 11 to 13+6 weeks was
assessed through linear regression analysis, and rates and outcomes of
persistently increased nuchal translucency above the
99th percentile (3.5 mm) were reported. For this
purpose, adverse outcomes were defined as at least one of miscarriage,
termination of pregnancy, relevant chromosomal abnormality or major
structural defects.
A two-tailed 0.05 significance level was adopted, and statistical
analyses were performed in SPSS version 25.0® (IBM
Corp. Released 2017. IBM SPSS Statistics for Macintosh, Version 25.0.
Armonk, NY: IBM Corp.).