While the licensed maximum dose is currently 20 mU/min, some clinicians support the use of regimens up to 40 mU/min. The appropriate dose of syntocinon remains controversial, but there is good evidence for starting at a low dose, around 0.5–4 mU/min, and increasing over 4 or 5 h to 12 mU/min. The choice of dosage regimens for each represents a compromise between efficacy and the risk of hyperstimulation. Both syntocinon (synthetic oxytocin that is administered by injection or infusion) and prostaglandins may be implicated. Uterine hyperstimulation occurs much more commonly, however, and by definition is caused by the use of oxytocics. Spontaneous uterine hypercontractility may be associated with placental abruption (see p. The contractions may be excessively long in duration or be excessively frequent and there is a risk of fetal hypoxia due to interference with the placental blood supply. Spontaneous hypercontractility is rare, perhaps occurring in only 1:3000 pregnancies. It is subdivided into ‘true’ cephalopelvic disproportion if the head is in the correct position and ‘relative’ cephalopelvic disproportion if the obstruction is caused by the head presenting in a position other than occipitoanterior. Slow labour may result from inadequate uterine activity, cephalopelvic disproportion, or more commonly, a combination of the two.Ĭephalopelvic disproportion refers to how well the fetal head fits through the pelvis and may occur if the fetal head is too big or the pelvis too small. Precipitate labour has been defined as expulsion of the fetus within less than 3 h of the onset of contractions and results from uterine overactivity. In practice, overactivity presents as rapid painful contractions often associated with fetal distress, and inadequate uterine activity as absent or slow cervical dilatation.

It is tempting to refer to uterine ‘overactivity’ as that which results in labour progressing too quickly, and ‘inadequate’ uterine activity as that which is insufficient to provide adequate progress, but the rate of progress has no precise definition either and is dependent on parity.

Abnormal uterine activity has no clear definition, partly because the range of normal uterine activity itself has no clear definition.

Complications of precipitate labor