The influence of elective amniotomy on fetal heart rate patterns and the course of labor in term patients: a randomized study.

OBJECTIVES

Our study was designed to evaluate the effects of routine elective amniotomy on the frequency and severity of abnormal fetal heart rate patterns and on the course of labor and the need for oxytocin augmentation.

STUDY DESIGN

A randomized, controlled trial was conducted at term in patients in active labor who were randomly selected to undergo elective amniotomy (amniotomy group) or left intact with amniotomy reserved for specific indications (intact group).

RESULTS

Four hundred fifty-nine patients were studied (235 in the amniotomy group vs 224 in the intact group). Average cervical dilatation at rupture was 5.5 cm in the amniotomy group and 8.1 cm in the intact group. Analysis of fetal heart rate revealed more mild and moderate variable decelerations in the active phase of labor in the amniotomy group but no difference in the frequency of more severe decelerations or operative deliveries. In the intact group the need for oxytocin was twice as common (76 in the intact group vs 36 in the amniotomy group, p = 0.000005), and the active phase of labor was considerably longer (5 hours 56 minutes in the intact group vs 4 hours 35 minutes in the amniotomy group). Neonatal outcome was similar in the two groups.

CONCLUSIONS

Elective amniotomy appears to increase the likelihood of umbilical cord compression in the active phase of labor and results in more mild and moderate variable decelerations, but it does not result in more severe abnormal fetal heart rate patterns or more operative intervention. Elective amniotomy does, however, shorten the active phase of labor and decreases the need for oxytocin augmentation.