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Induction of Labor

The incidence of induction of labor has increased at significant rates for the past 10 years. The incidence of inductions has doubled roughly induce labor. One recent study demonstrated pretty conclusively that in a group of nulliparous patient’s after controlling for various factors such as cervical dilation, station, things like that, we do know that induction of labor is associated with a roughly twofold increased risk of cesarean section, the odds ratio in that study was two.

To begin discussing induction, you always sort of have to begin with a discussion of the cervix. This is sort of the basic element of induction is the course of induction and the choice of the type of induction always relates to what the cervix is and gets around to talking about the Bishop score. Initially described in the 1940s, the Bishop score was actually when initially described, had nothing to do with induction of labor, in fact the Bishop score was initially described or was designed in effort to predict in multiparous patient’s the duration from the time of exam to spontaneous labor.

The ideal cervical agent you are going to use to improve your Bishop score should have a number of different components. First and foremost it should be safe, you would like it to be fast, you would like minimal side effects, and as little patient discomfort as possible, you would like it to be inexpensive, and obviously you would like it to result in few failed inductions and you would like to have a low cesarean section rate. So when we discuss the studies later on that compare different types of agents, these are some of the outcomes that we are going to look at to see if agents that we are discussing meet these goals.

The hormonal and biochemical changes that you see with cervical ripening are many, we are not really going to go into this in detail, but you do see when you go about ripening a cervix changes in the hormonal milieu and that you will find decreased progesterone collagen production, you can read the others, they should be in your handout, but there is a very real biochemical in addition to mechanical reason as to why cervical ripening will work and increase your likelihood of successful induction of labor.

There are obviously concerns about amniotomy especially in the setting where you are not able to do increasing monitoring and quick cesarean section, there are risks of increased infection, increased risk of cord prolapse, especially with an unengaged head, and as I said, it’s used in many parts of the world as a primary strategy for induction.

Osmotic dilators such as Laminaria are another well known ripening agent, the way they work as we know they absorb water, so they act as a mechanical dilator to slowly dilate the cervix, by doing so, they allow for amniotomy so you can use them in combination. One of the advantages to these is that you can theoretically use them in an outpatient setting and they change the Bishop score and shorten labor.

Prostaglandins, some biochemical formulas, very exciting. There are various numbers of prostaglandin formulations that are used for cervical ripening and induction, here you will see a number that we will be discussing, the prostaglandin E2, dinoprostone known in clinical practice by two different names, the dinoprostone is what makes up both the Prepidil gel used intracervically and the Cervidil vaginal insert, prostaglandin F2 alpha. The prostaglandin E2 derivative done in prostone are very commonly used as cervical ripening agents, the way in which they work, is they cause biochemical changes in the cervical composition themselves, they can stimulate contractions, there are relatively few contraindications.

This very busy slide is roughly a compendium of a number of trials that have looked at the odds ratio, the effectiveness of the cervical ripening agents, prostaglandin E2 in the cesarean section rate I believe and while the results are all over the place and very few of them in and of themselves meet significance meta analysis.

Some more details, outcomes of trials, in this case 70 to 100% entered labor, fewer than that needed oxytocin. There is varying degrees of tachy systole associated with varying regimens and dosages, there are shorter intervals to delivery and there is a question as to whether or not there is a lower cesarean section rate. Again, not to beat a dead horse, but in the evaluation of cesarean section rates, it is always important to know what population you are looking at, which are comparing it to and controlling for the other factors that will in and of themselves affect the cesarean section rate.

Some of the advantages, it obviously is quite effective at achieving dilatation allowing for amniotomy, it’s pretty low cost, doesn’t require a great deal time, it’s taken out in six hours if not sooner in the event of ruptured membranes or over distension and it shortens the induction time which is what we want in a ripening agent. So finally to look at comparative trials of all these different various methods.

To discuss cost briefly, because I think it is very important to discuss, one thing to keep in mind if you’re looking at studies discussing cost is the difference between cost and charge. This can often be confused in the literature and can very widely, what cost refers to is the actual cost of the technique or technology itself. So what the individual Prepidil may cost in this case, $74.00 per dosage and when you are going to calculate costs, you want to look at the individual cost and you also want to look at the total costs involved which may very well include the amount of time that the patient was there because that is going to include other costs, the number of dosages that you are using if you needed three Prepidil.