Inductions and The Bishop Score

Readiness for labor and inductions

Is my cervix ripe or ‘favorable’?

The success of an induction will usually depend on the woman’s physical ‘readiness’ for labor. The type of induction method selected will also be decided on this issue. If the decision is made to induce the labor, then the chosen method(s) will depend on:

The ripeness of your cervix. The cervix changes in consistency, and position, towards the end of pregnancy and during labor. For most of the pregnancy the cervix lies towards the back of the vagina, behind the baby’s head. This is called a ‘posterior cervix’ and is often hard to reach by the caregiver if they are performing a vaginal examination. Near the time of labor and / or during pre-labor and early labor, the cervix starts to move towards the front of the baby’s head. This is known as either a ‘central’ or ‘anterior cervix’ (depending on how far forward it has moved), and can usually be easily felt by the caregiver if being examined. The cervix also changes from being very firm and closed during pregnancy, to being soft to touch and slightly open just before labor starts.

The position, softness and openness of the cervix are usually assessed by the caregiver to determine what induction method will be used and / or whether the induction is likely to succeed. A more posterior, firmer and closed cervix has a higher chance of not responding to the induction, (meaning the induction is not successful and a Caesarean may be needed). If this is the case, the caregiver may utilize various methods to ‘ripen the cervix’ before inducing the labor. (Taking into consideration that the ‘ripening’ methods may also produce unwanted side effects). In some cases, the methods used to ripen the cervix will also succeed in inducing the labor.

Whether it is your first or subsequent baby. Women who have experienced labor before tend to be much more responsive to a wide range of induction methods and are less likely to have an unsuccessful induction. This also means they usually need less intervention to actually start the labor. For example, a woman having her second or subsequent baby is more likely to labor after just breaking the waters. This is unlikely to be enough to stimulate labor with a first time mother. However, women having subsequent babies are more likely to experience side effects from induction methods using medications. It is for this reason they are usually given lower doses of the drugs than first time mothers.

Why the induction is needed. Some health complications for mother (and / or baby) are regarded as not being suitable for the use of certain medications for induction. The use of an Oxytocin drip and / or Prostaglandins can have the potential to ‘over stimulate’ the uterus. (Or causing the uterus to contract ‘too much’). This can often lead to distressing the baby (not ideal if the baby is already unwell), or putting excess strain on a scar from a previous Caesarean birth (known as a VBAC). You can read more in Class 9 – VBAC. In these circumstances mechanical methods of induction may be preferable.

Your caregiver’s preferences. Many caregivers will have their own personal preferences about the induction methods they tend to use. Sometimes this is because they believe one method is superior (or safer) to another. Others may just use the method they are ‘used to’. A few may be keen to try out an experimental method new to the market! Occasionally the choice will be limited to what is available (for example, some hospitals will only stock one brand of Prostaglandins). If you learn about an induction method that you feel you might prefer, (but your caregiver has not offered it to you) you might like to suggest it as a possible option to be discussed. 

Is my cervix ripe or ‘favorable’?

 Bishop’s score

The success of many induction methods will usually depend on the woman’s physical readiness for her labor. The key physical sign of her readiness is the ‘ripeness’ or ‘favorability’ of her cervix. This is determined by an internal vaginal examination.

As the pregnancy draws to a close the cervix will usually start to soften, thin, move towards the front of the baby’s head and open slightly. This is called ‘cervical ripening’ and is associated with collagen breakdown (and rearrangement of collagen fibers) in the cervix. The more ‘ripe’ the cervix is, the more likely it will be to open when the contractions start.

An ‘unripe’, or ‘unfavorable’, cervix is usually not ready to respond to labor contractions. Therefore, it is less likely to dilate in response to certain induction methods, (such as an Oxytocin drip and breaking the waters). If the cervix does not dilate, the induction is regarded as unsuccessful, and a Caesarean would be required. To increase the success of inductions, medications (called ‘prostaglandins’) have been developed, aimed at ripening the cervix before the Oxytocin drip is given and the waters are broken. Prostaglandins are placed into the woman’s vagina (around her cervix), often helping the induction to be successful. In some cases, the prostaglandins start the labor on their own, without any further interventions. However, prostaglandin medications can have serious side effects and are not always the answer.   

Bishop’s score.
To help the caregiver assess which type of induction method is appropriate, they will usually assess the ripeness of the woman’s cervix using a scoring system, called the ‘Bishop’s Score’. The caregiver determines the score by feeling the woman’s cervix. The higher the score, the riper (or more favorable) the cervix is. Be aware that the interpretation of how the cervix feels (and therefore the score that is given) can vary from caregiver to caregiver.

Features of the cervix

Bishop’s Score

Score given

0

1

2

3

Dilation of the cervix (cms)

Closed

1 – 2 cms

3 – 4 cms

5 + cms

Consistency of cervix

Firm

Medium

Soft

Not Applicable

Position of cervix

Posterior

Midline or Central

Anterior

Not Applicable

Effacement (thinning) of cervix

0 – 30%

40 – 50%

60 – 70%

80% +

Station of head (How engaged?)

– 3

– 2

– 1 to 0

+ 1 to + 2

 

 

The 4 categories of the Bishop’s scoring system are as follows:

 

The consistency of the cervix.
The position of the cervix.
The thinning (or ‘effacement’) of the cervix.
How engaged the baby’s head is.

Each category is given a score of 0, 1, 2, or 3. The scores are then added up to give a final score to assess the likely success of an induction (or whether prostaglandins might be given).

A score of 0 – 4 means the cervix is unfavorable.
A score of 4 – 8 means the cervix is starting to become favorable.
A score of 8 – 14 means the cervix is very favorable.————————————————————————————–

(from http://www.birth.com.au/Home.aspx)

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