Statistical analysis
Statistical analysis was performed using an SPSS 26.0 software package and SAS 9.4. Characteristics of index and subsequent pregnancies were compared using paired t-tests for parametrically distributed data and Wilcoxon signed-rank tests for non-parametrically distributed data. Differences in proportions of dichotomous variables between index and subsequent pregnancies were analysed using McNemar’s test. Chi-squared tests were used to calculate the relative risk (RR) of adverse outcomes in subsequent pregnancies. Characteristics of subsequent pregnancies with and without LGA, with and without SGA, and with and without the composite neonatal outcome were compared using independent t-tests for parametrically distributed data, Mann-Whitney U tests for non-parametrically distributed data and chi-squared tests for dichotomous variables.
Binomial regression analysis was performed to estimate the RR of recurrent SGA, LGA or composite ANO in a subsequent pregnancy. Potential factors identified on univariate analysis were included in the model and backward stepwise removal was performed in order to identify independent predictors of each outcome of interest and their adjusted RR.
Results are expressed as mean and standard deviation for parametric data and median and interquartile range for non-parametric data, unless otherwise stated. Critical significance is taken at 5%.