Objective: To investigate the relationship between intrauterine pressure and the application of a standardised fundal pressure manoeuvre, and to determine the maternal, fetal and labour characteristics that modulate the relationship.
Design: Prospective measurement of intrauterine pressure during the second stage of labour.
Setting: North American university hospital.
Population: Forty full-term women in spontaneous labour were studied during the second stage. Each woman acted as her own control. All women laboured with requested epidural analgesia.
Methods: A fundal pressure manoeuvre was performed so as to standardise the level of force and the surface area of application. Intrauterine pressure was measured using a sensor-tip catheter. Five interventions were analysed: 1. valsalva during a uterine contraction; 2. fundal pressure and valsalva during a contraction; 3. fundal pressure during a contraction without valsalva; 4. fundal pressure in the absence of uterine contractions; and 5. valsalva in the absence of uterine contractions.
Results: Women in the second stage of labour transiently increased their expulsive force (as reflected by intrauterine pressure) by 86% of their baseline contraction using valsalva and fundal pressure simultaneously. The efficiency by which both contraction-enhancing manoeuvres increased intrauterine pressure was directly related to gestational age and inversely related to myometrial thickness.
Conclusion: Fundal pressure applied under controlled conditions significantly increases intrauterine pressure in some, but not all women. Simultaneous measurement of intrauterine pressure, to maintain feedback during application will create a 'controlled environment' for the obstetrician and reassurance that this manoeuvre can be applied in a controlled fashion. Future delineation of the group of women that could benefit from fundal pressure, as well as the group that is refractory is essential to avoid unnecessary or delayed operative interventions.