Data analysis
Descriptive analyses were performed to compare the maternal and fetal
demographic and outcome variables for the three groups: land, water, and
WWI-only births. For some analyses the water birth and WWI groups were
combined into a single group (highlighted in the text below). Data are
presented using median and inter-quartile range (IQR) for continuous
data (due to skewed distributions), frequencies and proportions for
categorical variables. Chi-square tests were performed to investigate
associations between the groups (land, water, WWI) and categorical
variables (e.g., NNU admission, perineal damage). Chi-square tests and
Mann-Whitney U-tests were used to look for associations between NNU
admission and maternal variables. Multivariate logistic regressions were
used to model the odds of NNU admission, where variables were selected
for inclusion based on their clinical relevance. These models contained
the following variables: birth group (WWI vs waterbirth vs land birth;
maternal age, maternal BMI, previous birth mode, epidural use, length of
labour (1st + 2nd stage) and labour
onset. All analyses were performed in R (version 4.0.2).