Clinical considerations
Prior to embarking upon an induction, one must be sure of the gestational age and presentation. Additionally, the indication for induction must be agreed with the woman and clearly documented.
Fetal health should be confirmed by external electronic fetal heart monitoring before starting the induction. If there is evidence that the fetus would not tolerate an induction this is best known prior to administering any medications or performing any procedures to begin the induction. The modified Bishop score, as discussed previously, should also be calculated to decide on the need for pre-induction cervical ripening.An induction of labour should ideally be carried out in settings with electronic fetal monitoring, facilities for accurately measuring infusion rates, and access to emergency caesarean section.
Outpatient induction is an option for some women, but it should be limited to the use of methods with low rates of hyperstimulation (e.g. mechanical methods, nitric oxide donors, or controlled release prostaglandins). RCTs suggest no difference in clinical outcome between inpatient and outpatient inductions except that outpatient inductions are associated with higher maternal satisfaction rates (28). One recent Australian study of inpatient versus outpatient use of a Foley catheter (see ‘Transcervical balloon catheters') showed that the outpatient group was 24% less likely to require oxytocin to achieve vaginal delivery (29).
Ideally, an induction should be started in the morning as they are associated with higher maternal satisfaction and lower operative vaginal delivery rates. If intermittent fetal monitoring is used, it should be conducted before and after every drug administration and once contractions start. Once in labour, most women have continuous monitoring. However, it is safe to forego continuous monitoring in uncomplicated pregnancies without a fetal indication for induction and where oxytocin is not needed for augmentation (8).
Induced labours are more painful than spontaneous labours. However, women (and staff) can be reassured that administering epidural analgesia prior to painful contractions or in early labour has no adverse effects on clinical outcomes and increases maternal satisfaction.A risk of all inductions of labour is hyperstimulation, also known as tachysystole. Hyperstimulation is defined as more than five contractions in 10 minutes averaged over 30 minutes (30). Not all fetuses exposed to hyperstimulation will have fetal heart rate abnormalities, but data from the Parkland Hospital (Dallas, Texas, United States) state that six contractions in 10 minutes is when the rate of fetal heart tone decelerations rapidly increased (30). When using pharmacological methods of induction, uterine hyperstimulation occurs in about 5% of women. One-third of these women will also have fetal heart rate abnormalities (a combination known as ‘hyperstimulation syndrome'). Hyperstimulation can be rapidly reversed by stopping an oxytocin infusion, or removing an intravaginal induction system. For those in whom the induction agent cannot be removed or stopped, beta-2-adrenergic therapy (e.g. terbutaline 250 mcg given subcutaneously or intramuscularly) is very effective and without maternal or fetal complications (31).