The 'success' of prostaglandins, will depend on what you are expecting it to achieve. If giving the prostaglandins is intended to just ripen the woman's cervix (before using an oxytocin drip), then it is likely to achieve this, (although more than 2 doses may be required). This may be the case if the labour is being induced before 41 weeks of pregnancy, when the woman's cervix is usually unfavourable (and induction with just an oxytocin drip and breaking the waters is more likely to be unsuccessful). It is also more likely if it is your first baby.
If your expectation is to induce the labour with just prostaglandins, this will be more likely to succeed the more overdue you are (and the riper your cervix is), or if this is your second, or subsequent, baby. The most common scenario in this case is the woman has one to two doses of prostaglandins, inducing early labour and dilating the cervix to about 3 to 4 cms, then the caregiver breaking the waters, to stimulate the labour to continue until the baby is born. For women who respond well to prostaglandins and start to labour strongly, the waters may not need to be artificially ruptured, but allowed to break on their own (this is more likely if it is your second or subsequent labour).
If the 2 doses of prostaglandins and breaking the waters do not start the labour (being judged about 6 to 8 hours after the 2nd dose), you would probably need to go to the delivery suite for an oxytocin drip. If the prostaglandins do not change the woman's cervix significantly, or stimulate contractions, some women will negotiate for their waters not to be broken, and ask for the induction to be delayed a day or so (if this is feasible). The 2 doses of prostaglandins may be tried again at a later stage and may avoid the need to use oxytocin. Often the second attempt with prostaglandins is more successful (or not needed), because the labour starts before this.
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