Primiparas with or without oxytocin augmentation: a prospective descriptive study

Abstract

Aims: The aim of this study was to determine during which phase of delivery augmentation is started when used and to establish any correlation that might exist between the oxytocin infusion and the evaluations by primiparas themselves of their labour pain, strength of contractions and fatigue. In addition, we wanted to determine any differences in duration between labour with and labour without augmentation. We finally wanted to measure the incidence of instrumental deliveries, perineal trauma and neonatal outcome among the augmented vs. the non-augmented groups.

Background: The most commonly diagnosed complication in primiparas is ineffective contractions or protracted labour, otherwise known as dystocia, which literally means arrested or prolonged labour. Different treatments have been tried during the active phase of labour as well as the second stage of labour. The most common treatment today is amniotomy, often used in combination with an intravenous oxytocin infusion.

Materials and methods: The study was conducted at the hospital in Ostersund in central Sweden from August 1998 to September 1999. Consecutive primiparas giving birth at full-term were selected to the study. The inclusion criteria were an uncomplicated pregnancy and a spontaneous single delivery with head presentation. The total number of participants was 164.

Results: The results showed that 50 of 164 primiparas needed no augmentation, while 88 were augmented during the active phase and 26 during the second stage of labour. The duration of the active phase [median (md) 4 hours 45 minutes, 6 hours 49 minutes and 6 hours 20 minutes respectively for the different groups, P = 0.03], the time between full dilation of the cervix and the start of the second stage (md 20 minutes, 30 minutes and 60 minutes respectively, P = 0.012) and the duration of the second stage of labour (md 40 minutes, 44 minutes and 60 minutes respectively, P = 0.04) were significantly longer in the augmented groups. Operative deliveries, too, were more frequent in the augmented groups. There was a significantly higher rate of perineotomies in the group augmented during the second stage of labour. There were, however, no differences in Apgar score <7 at 1 minute. pH in the umbilical cord and the base deficit were higher in the group which were augmented during the second stage of labour (P = 0.02 and P = 0.06 respectively). Women describing their impression of the experience as a whole generally gave it a high rating, but women who were augmented during the second stage of labour gave the experience a significantly lower score (P = 0.01).

Conclusion: Augmentation is used in unusually prolonged deliveries. We did not find that augmentation involved a higher frequency of perineal trauma, although it was correlated with a higher frequency of operative deliveries. There was no correlation between the oxytocin infusion and the primiparas' descriptions of the strength of contractions, pain and fatigue, although greater use of epidurals was observed in women with augmented labour. The number of nulliparas in this study was too small to analyse the incidence of ruptures in the sphincter or draw conclusions about differences between the groups with regard to Apgar scores or metabolic acidosis.

Relevance to clinical practice: In clinical practice, good routines concerning oxytocin augmentation are crucial. Interventions as oxytocin augmentation seem to cause harm to mother and child. To evaluate interventions continuously in obstetric care is therefore important.