Strengths and Limitations
This study suffers from a number of limitations. First, its cross-sectional design precludes any confirmation of causality. However, it is implausible that cord blood gas status should have an influence on abdominal musculature. Second, reductions in the sample size for some variables could have prevented significance being reached for some associations. The study also has some strengths that should be highlighted. First, the measurement of gases in the arterial CB is the gold standard for examining the acid-base status of the foetus. Second, venous and arterial CB samples were taken to allow for better interpretation of the results. Third, muscle thicknesses and the IRD were measured by ultrasonography - a reliable and risk-free method for pregnant women24. Finally, to the best of our knowledge, this is the first study providing a comprehensive examination of the associations shown by objectively measured abdominal muscle thickness and the IRD, with cord blood gases at birth.