Labour induction and augmentation
Labour induction
As the end of pregnancy nears, the cervix normally becomes soft (ripe) and begins to open (dilate) and thin (efface), preparing for labour and delivery. When labour does not naturally start on its own and vaginal delivery needs to happen soon, labour may be started artificially (induced).
Even though inducing labour is a fairly common practice, childbirth educators encourage women to learn about it and about the medicine for stimulating a stalled labour (augmentation) so that the women can help decide what is right for them.
When labour does not happen as expected or as necessary, inducing labour is preferred over delivering by caesarean section. If labour induction isn't successful, another attempt may be possible. In some cases, a caesarean delivery is best for the mother and baby, depending on their conditions.
There are several ways to induce labour contractions.
- If your cervix is not ripe, medicine is first used to soften it and help it thin (efface).
- If your cervix is ripe but active labour has not started, contractions may be induced by sweeping the membranes or rupturing the amniotic sac (amniotomy).
- If labour does not progress after an amniotomy, medicine such as oxytocin (Pitocin) can be used to stimulate contractions.
Your labour may be induced for one of the following reasons:
- Your pregnancy has gone 1 to 2 weeks past the estimated due date.
- You have a condition (such as high blood pressure, placenta abruptio, infection, lung disease, pre-eclampsia, or diabetes) that may threaten your health or the health of your baby if the pregnancy continues.1
- Your water (amniotic sac) has broken, but active labour contractions have not started.
- Your baby has a condition that needs treatment, and the risks of vaginal delivery are low. Induction and vaginal delivery are not attempted if the baby may be harmed or is in immediate danger. In such cases, a caesarean delivery (C-section) is usually performed.
Medication to ripen the cervix and induce labour
- Misoprostol (Cytotec) is a pill taken by mouth or placed in the vagina (using a smaller dose). It is a medication currently approved for treating ulcers. Using it for cervical ripening is a widely accepted but unlabelled use of this medication.2
- Oxytocin (Pitocin) can be given through a vein (intravenously) in small amounts to ripen the cervix. But it usually is given after the cervix softens, to cause the uterus to contract. Labour that is induced by oxytocin usually starts off harder and progresses faster than labour that starts on its own, especially in first-time mothers. If oxytocin does not induce labour or if the baby's heart rate indicates distress, a caesarean delivery (C-section) may be necessary.
- Dinoprostone (such as Cervidil or Prepidil Gel) can be inserted as a suppository into your vagina (intravaginally). It can also be given as a gel that is gently squirted into the opening of the cervix (intracervically). When the cervix is ripe, labour may start on its own.
In some centres, a balloon may be inserted in the cervix and gently inflated to help induce labour.
The cervix is considered ripe and ready for active labour when it is soft, well-dilated, and effaced, and when the cervix and baby are positioned low in the pelvis. If the cervix is not ripe enough, medicines may be continued until it is.
Sweeping of the membranes to help induce labour
Sweeping, or stripping, of the amniotic membranes is a simple first step used to try to start labour. Sweeping of the membranes separates the amniotic membrane from the uterus enough so that the uterus starts making prostaglandins. This type of chemical helps trigger contractions and labour. After the cervix is open a little, this step can easily be done in your doctor's or nurse-midwife's office.
Sweeping the membranes works in 1 out of 8 women. This means that it starts labour without needing to use oxytocin or artificially rupture the membranes.3 To sweep the membranes, your doctor or nurse-midwife reaches a gloved finger through the cervix. He or she then "sweeps" the finger around the inside edge of the opening.
Sweeping the membranes is low-risk. It does not raise your risk of infection. You may start to feel uncomfortable afterward, with irregular contractions and some bleeding.3
Artificial rupture of the membranes to induce labour
To help start or speed up labour, your health professional may rupture your amniotic sac (rupture of the membranes). This should only be done after your cervix has started to open (dilate) and the baby's head is firmly descended (engaged) in your pelvis. If the membranes are ruptured too early, there is a risk of the umbilical cord slipping down around or below the baby's head (cord prolapse). If the cord gets squeezed between the baby's head and the pelvis bones, the blood supply to the baby may be decreased or stopped.
To rupture your amniotic sac (amniotomy), your health professional inserts a sterile plastic device into your vagina. This device may look like a long crochet hook or may be a smaller hook attached to the finger of a sterile glove. The hook is used to pull gently on the amniotic sac until the sac breaks. This procedure is usually not painful. A large gush of fluid usually follows the rupture of the amniotic sac. The uterus continues to produce amniotic fluid until the baby's birth, so you may continue to feel some leaking, especially right after a hard contraction.
Augmentation
If active labour has started on its own but contractions have slowed down or completely stopped, steps need to be taken to help labour progress (augmentation). Augmentation will be done when:
- Active labour has started, but your contractions are weak or irregular or have stopped entirely.
- You have gone into active labour, but the amniotic sac has not ruptured on its own. In this case, your doctor or nurse midwife may rupture the amniotic sac (amniotomy) to augment labour. If labour still does not progress, oxytocin (Pitocin) may be given to make the uterus contract.
- Active labour has started and the amniotic sac has ruptured on its own, but labour still is not progressing. Oxytocin (Pitocin) may be given to make the uterus contract.
For some women, labouring in a warm tub or whirlpool (under medical care) helps with a slow labour. This can make augmentation unnecessary.4
If labour fails to progress in spite of membrane sweeping, an amniotomy, oxytocin, or a combination of these measures, delivery by caesarean section may be considered.
| Author: | Bets Davis, MFA Kathe Gallagher, MSW Ralph Poore | Last Updated: February 26, 2008 |
| Medical Review: | Sarah Marshall, MD - Family Medicine Adam Husney, MD - Family Medicine Kirtly Jones, MD - Obstetrics and Gynecology Deborah A. Penava, BA, MD, FRCSC, MPH - Obstetrics and Gynecology | |
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