The Bearing-down Efforts and their Effects on Fetal Heart Rate, Oxygenation and Acid Base Balance.

The Valsalva maneuver duration during labor expulsive stage: repercussions on the maternal and neonatal birth condition

“…When the VM duration increased, the arterial base excess decreased; however, no relationship was observed with arterial PCO 2 . Caldeyro-Barcia et al 8 reported higher levels of venous and arterial pH in a sample of women in labor who used the VM with an average duration of 5 s. This finding support that VM duration is an important variable with respect to maintaining optimal acid base balance.…”

“…However, umbilical blood gases were not evaluated in these studies, and no differences in the duration of the expulsive stage between breathing techniques were found. CaldeyroBarcia et al 8 and Thompson 16 reported a shorter expulsion time in women who used VM, however; umbilical pH was negatively affected.…”

“…We recommend that this parameter be included in future studies. Pushing in conjunction with a VM has been associated with fetal heart rate changes including prolonged deceleration and bradycardia consistent with a hypoxemic response 8 . These reports confirm the need for greater understanding about normal breathing and pushing efforts in women in labor to guide the development of more refined clinical practice guidelines to support women during childbirth and delivery.…”

“…Some investigators; however, have argued that breathing control interventions should not be imposed. Rather, the mother should adopt a breathing pattern including the VM in accordance with what she instinctively requires [7][8][9] . When a woman who is delivering breathes in accordance with her needs rather than having a pattern imposed, her respiratory efforts typically involve breathing with an open glottis, rather than a closed glottis, such as the case during a VM, and when she uses the closed glottis is only for a maximum of 4 to 6 seconds 9 .…”

“…Some physiologic evidence supports the avoidance of VMs of 10 seconds or more during labor and delivery 6 . Despite several papers 4,5,[7][8][9] supporting its adverse maternal and fetal effects, prolonged VMs continue to be promoted in the literature. Futhermore, no study to date has specifically examined the relationship between the VM and its duration, on maternal and neonatal outcomes, and the implications for recommendations regarding preparation for childbirth.…”