Abstract
This investigation was carried out to determine whether paracervical block (PCB) has any effect on the duration of the first stage of labour, relating the speed of cervical dilatation to uterine activity. Uterine activity was measured by internal tocometry and calculated in Montevideo units (MU).
Fourty patients were selected and allocated in random manner to a PCB or a control group, the patients in the latter receiving other kinds of analgesia. Oxytocin was given when required, to assure a steady and fairly high degree of uterine activity. Four patients were excluded.
The mean duration of the first stage of labour, from cervical dilatation 2 to 10 cm, was 161 minutes in the PCB group, 237 minutes in the control group.
Uterine activity, calculated as total MU needed for each cm of cervical dilatation, was reduced after PCB, the differences being statistically significant for increments from 3 to 8 cm cervical dilatation inclusive.
PCB caused a transient reduction in frequency of contractions, and a relative fall in amniotic pressure between contractions.
It is concluded that PCB facilitates cervical dilatation by inhibiting muscular contraction in the lower uterine segment.