RESULTS
Of the subjects who met the eligibility criteria and agreed to participate, 159 completed the first assessment (Figure 1 ). Among them, 158 (age 32.9±4.6 years, BMI 24.9±4.1 kg/m2) provided sociodemographic data and were included in the present analyses. Table 1 shows these data along with the subjects’ clinical characteristics. Most of the study subjects (97.5%) lived with a partner and had a university degree (60%). Almost all gave birth at a public hospital (94%) at around the 40th w.g; approximately 60% of all births were eutocic. At the 34th w.g., the IRD 50th percentile was 46.3 mm at rest and 40.7 mm during crunches. Table 2 shows the Pearson partial correlations between the average abdominal muscle thickness at 34thw.g. and maternal and neonatal birth outcomes. After adjusting for the aforementioned confounders, abdominal muscle thickness and IRD were found not to be related to the duration of the first and second stages of labour (all p >0.05). Greater TrA and IO thicknesses were associated with higher venous CB PO2 at rest (r=0.326 p =0.005, and r=0.261 p =0.0027, respectively) and during activation (r=0.249, p =0.037, and r=0.257p =0.031, respectively). A greater TrA thickness during activation was associated with a higher venous CB oxygen saturation (r=0.235,p =0.05). EO thickness at rest was positively associated with arterial CB pH (r=0.256 p =0.031), and in activation with the newborn’s 1-minute Apgar test score (r=0.216 p= 0.029). A greater IRD was associated with a higher arterial CB PCO2 (at rest, r=0.302 p = 0.01; during crunches, r=0.242 p =0.042) and venous CB PCO2 (at rest, r=0.246 p =0.028), and lower arterial CB PO2 (at rest; r = -0.256p =0.041; during crunches r=-0.287 p =0.021), arterial CB oxygen saturation (at rest, r=-0.264 p =0.038; during crunches r=-0.313 p =0.01), and venous CB oxygen saturation (during crunches, r=-0.251 p =0.039), and a more acidic arterial CB pH (during crunches, r=-0.231 p =0.05) and venous pH (at rest, r=-0.225 p =0.041; during crunches, r=-0.240 p =0.039).
No differences were seen between subjects with an IRD above or below the median in terms of the duration of the first and second stages of labour, or in terms of their offsprings’ Apgar test scores (data not shown). Figure 2 shows the differences in CB gas values for the subjects with IRD above and below the median value. After adjusting for potential confounders, neonates born to women with an IRD during crunches equal to or greater than the median value had arterial CB with a more acidic pH (Figure 2A, p =0.038), a higher PCO2 (Figure 2B, p =0.029) and a lower PO2 (Figure 2C, p =0.005) and oxygen saturation (Figure 2D, p =0.004) than did those born to women with an IRD below the median. Finally, the offspring born to women with an IRD at rest equal to or greater than the median showed a lower arterial CB PO2 (Figure 2E, p =0.041) than did those born to women with an IRD at rest below the median. No differences were seen with respect to the duration of the first and second stages of labour, or any other CB gas values (allp >0.05, data not shown).