Uterine contraction pattern as a predictor of the mode of delivery.
OBJECTIVE
To determine whether analysis of the frequency or regularity of uterine contractions can distinguish between women delivering vaginally and women requiring Cesarean section for dystocia.


METHODS
This was a case-control study. Cases meeting the following criteria were identified: nulliparous women in spontaneous labor, singleton pregnancy, cephalic presentation, 37 to 42 weeks' gestation, Cesarean section for dystocia, a minimum of three analyzable hours of electronically archived cardiotocograph (CTG) prior to onset of the second stage. Cases delivered by Cesarean section for dystocia were each matched with two controls delivering vaginally. The peak of each contraction was visually identified and electronically marked on each CTG trace. A moving average (MTIME) and standard deviation (SDTIME) of five interpeak times were calculated for successive 30-minute periods and plotted against cervical dilatation for each group.


RESULTS
Overall, both MTIME and SDTIME fell as labor progressed, with these changes being more marked in the vaginal delivery group. In women requiring oxytocin, the rate of fall of MTIME and SDTIME was significantly greater following oxytocin in the group which subsequently delivered vaginally (slope of MTIME -2.71 pre-oxytocin and -28.95 post-oxytocin, p=0.0004; slope of SDTIME -0.44 and -6.44, p=0.0002). No such change was seen in the Cesarean section group.


CONCLUSIONS
As normal labor progresses, there is a shortening of the intercontraction interval and an increase in contraction regularity. A successful response to oxytocin augmentation may be predicted by the change in contraction pattern following treatment.
Oppenheimer
Lawrence W
LW
Division of Perinatology, Ottawa General Hospital, Ottawa, Ontario, Canada.
Bland
Elaine S
ES
Dabrowski
André
A
Holmes
Paul
P
McDonald
Omid
O
Wen
Shi Wu
SW
D016022:Case-Control Studies; D002585:Cesarean Section / Q000706:statistics & numerical data; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000379:methods*; D005260:Female; D005323:Fetal Monitoring / Q000379:methods; D005865:Gestational Age; D006801:Humans; D007745:Labor Onset / Q000502:physiology; D007751:Labor, Induced / Q000379:methods; D007744:Obstetric Labor Complications / Q000517:prevention & control; D010121:Oxytocin / Q000008:administration & dosage; D010298:Parity; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011336:Probability; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014590:Uterine Contraction / Q000502:physiology*
D010121:Oxytocin