Statistical analyses
Normality of the data was assessed by the Kolmogoroff–Smirnoff test and
data were expressed as mean (standard deviation) and median
(interquartile range) for normally and non-normally distributed data,
respectively. Categorical variables were expressed as number
(percentage). The groups were compared using the unpaired Student
t-test/Mann-Whitney or chi-square (χ2) for numerical
and categorical data, respectively.
Logarithmic transformation was performed for non-parametric data and
multilevel linear mixed-effects models were used to compare the groups.
The fixed effect component included time (the three study visits), study
group, maternal age, race, smoking, gestational age at the time of
echocardiography, development of GDM and first-order interaction between
time and study group. A higher numbers of cases compared to controls
were chosen in order to produce more precise effect measures, also
considering that echocardiographic data of pregnant women with normal
BMI has been previously reported; 8 our sample size
reflected a paucity of data in obese pregnant women. Considering a 4:1
ratio for cases and controls, our study had >80% power (at
alpha=0.05) to detect an 1829ml/min difference in CO, 0.12 difference in
E/A ratio and 65g difference in LV mass between groups.14 Statistical analyses were performed using
International Business Machines (IBM) Statistical Package for the Social
Sciences (SPSS) for Windows 2019, version 26.0, IBM Corp., Armonk, New
York, USA. Differences were considered statistically significant at
p<0.05.