Induction Part 2: Medical Methods
In the last post we talked about what an induction is and some of the reasons for one. In this post we will discuss the different methods of medical induction and how they work. There are some natural induction methods that can be tried at home, but it's a good idea to talk to your provider about these before you try them.
Before an induction the care provider will do a manual cervical exam to determine your dilation, effacement, and station. This will help them determine how ready your cervix is for labor and help them to decide what induction method they'd like to start with. Some providers use the Bishop Score to help with decision making.
Many inductions begin with Cervical Ripening. This is a way to get the cervix "ready" for labor. A common method of cervical ripening is using prostaglandins. These are synthetic forms of hormones your body already makes that can stimulate uterine contractions. These can be taken orally or be placed vaginally. Dinoprostone is the only prostaglandin approved by the FDA for induction of labor. Misoprostol is another common medication that is used off-label. This medication should not be used in anyone who has had a previous cesarean. These medications will cause contractions of the uterus which helps thin and dilate the cervix.
Mechanical methods mean anything that physically touches on the cervix to help it dilate. The cervix needs to be at least a little bit dilated in order for these methods.
A "membrane sweep" is when the provider inserts a finger into the cervix and sweeps around in a circle to separate the membranes of the amniotic sac (bag of waters) from the inside opening of the cervix. A Foley catheter or Cook Balloon is a flexible catheter which is placed inside the cervix, and a balloon at the end is filled with water. This balloon can put some pressure on the inside of the cervix to encourage opening. The Foley catheter only has one balloon. The Cook Balloon has a second balloon that sits outside the cervix in the vagina and applies pressure from the other side.
There are two types of absorbent rods (called osmotic dilators) that can be used for opening the cervix as well. Laminaria is made from sterilized seaweed, and Dilapan-S is a synthetic version. These are small, thin rods about the length of a toothpick, but a little bit wider around. Once the cervix has started to open these rods can be placed inside the cervix. They expand as they absorb fluids, and force the cervix open as they grow. I personally have never seen these used.
Once the cervix is softened Pitocin is usually given through a continuous IV infusion. Some people progress to active labor after prostaglandins and do not need any Pitocin. Pitocin is a synthetic version of the hormone oxytocin. It is chemically identical on a molecular level, but has some slight differences in the way it is delivered to the body and in how it effects pain and emotions. Pitocin is started at a very slow rate and increased throughout the day until you are having consistent contractions that are 2-3 minutes apart. If the contractions get too close together or last too long Pitocin can be turned down or off and the effects lessen within the next few minutes.
Once you are in a productive labor pattern, having regular contractions that are producing cervical change, the provider may want to perform an amniotomy. This means breaking the water manually. An amniotomy hook is a long slender rod with a tiny hook on the end. Think like a very long, very small crochet hook. It can be inserted into the vagina and used to break the amniotic sac. They slide the hook along the membrane until it catches and tears a hole. This is uncomfortable because of the hand and hook in the vagina, but the breaking of the sac is not painful. The amniotic sac doesn't have any nerves in it so it doesn't feel pain.
Once all these things have been used, ideally your body will make regular progress and result in the vaginal birth of your baby!
Check back next week for Part 3: Benefits and Risks of induction.