Statistical analyses
Subject sociodemographic and clinical characteristics, and abdominal muscle thicknesses, were recorded using descriptive statistics (mean±SD, number, or percentage as required). Since some variables (onset of labour, type of birth, sex of the baby) have been shown weakly related to the study variables21,22, their role as potential confounders was assessed. Finally, the associations shown by the thickness of the abdominal muscles and the IRD, with birth-related maternal and neonatal outcomes, were determined using partial Pearson correlations after adjusting for maternal age, parity, BMI at the 16th w.g., and gestational age at birth. Values for the duration of the first and second stages of labour, the Apgar test score, and CB gas variables were adjusted for epidural analgesia. Given that our group has previously described an association between maternal flexibility in the third trimester of pregnancy and CB gas values at birth23, the latter variables were adjusted for flexibility at the 34th w.g. Analysis of covariance (ANCOVA) was used to explore the differences in the duration of the first and second stages of labour, and in neonatal CB gas values, between women above or below the median IRD. Adjustments were also made for being in the control or exercise group within the broader GESTAFIT project14. All statistical analyses were performed using SPSS Software for Windows, v.20.0 (IBM, Armonk, NY, USA). Significance was set at p≤0.05.