Effect of Amniotomy on Uterine Muscle Electrical Activity During Labor Induction with Oxytocin and Prostaglandins

Other literature type English OPEN
Toth, Tibor (2006)
  • Publisher: Sestre Milosrdnice University hospital and Institute of Clinical Medical Research
  • Journal: Acta clinica Croatica (issn: 0353-9466, vol: 45)
  • Subject: Labor, induced - physiology; Labor, induced - methods; Uterus - physiology; Uterine contraction - drug effects; Oxytocin - therapeutic use; Prostaglandins - physiology | Porod, izazvani - fiziologija; Porod, izazvani - metode; Maternica - fiziologija; Maternična kontrakcija - učinci lijekova; Oksitocin - terapijska primjena; Prostaglandini - fiziologija

The aim of the study was to find out whether noninvasive recording of uterine muscle electrical activity could help monitor the development of mechanical myometrial activity during induced labor. Myometrium electrical activity during labor induction was analyzed in 110 gravidas hospitalized at Maternity Ward, Bjelovar General Hospital in Bjelovar. The means used for labor induction was oxytocin infusion in 54, intracervical prostaglandin (dinoprostone 0.5 mg) in 20, intravaginal prostaglandin (dinoprostone 2 mg) in 21, and intravenous prostaglandin (dinoprostone 0.75 mg) in 15 women. Electromyographic measurement was done at 30, 90, 150 and 270 minutes of the induction agent administration. In all pregnancies, silence of the uterus was electromyographically confirmed before the study. During the study, amniotomy was performed in 54 patients: soon after 1st measurement (30th minute of induced labor) in 6, after 2nd measurement (90th minute of induced labor) in 20, after 3rd measurement (150th minute of induced labor) in 10 and after 4th measurement (210th minute of induced labor) in 18 patients. Characteristics of electrical discharge were analyzed separately (number of impulses, amplitudes, series, shape) and each record was merged by index of uterine activity according to .krablin­Kuèiæ formula: uterine activity index (UAI)=number of impulses during 10 minute period + amplitude (µV) of highest potential divided by 100, by which the series of discharge were marked by additional 20, biphasic waves with 2, and polyphasic with 3 points. Statistical analysis of EMG UAI values obtained on oxytocin labor induction according to modified Bishop cervical index and amniotomy yielded statistically significant differences in the EMG UAI value increase between the patients with and without amniotomy (p<0.05). On measurements done at 210 and 270 minutes at Bishop index >8, the values of UAI after amniotomy were not statistically significant (p>0.05). Analysis of EMG UAI values in patients administered intracervical prostaglandin for labor induction revealed a statistically significant difference between patients with and without amniotomy (p<0.05). Analysis of EMG UAI values in patients administered intravaginal (dinoprostone 2 mg) and intravenous (dinoprostone 0.75 mg) prostaglandin preparation for labor induction showed no statistically significant difference between patients with and without amniotomy (p>0.05). Accordingly, recording electrical myometrial activity before and after amniotomy by transcutaneous uterine electromyography during labor induction showed positive correlation with the course and outcome of induced labor, which may prove useful in the induced labor monitoring and guidance.
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