The frequency of induction varies by location and institution. The rate of induction in Canada has increased steadily from 12.9% in 1991–1992 to 19.7% in 1999–2000. The rate reached a high of 23.7% in 2001–2002, decreased slightly to 21.8% in 2004–2005, and has since remained steady. The 2010 BC Perinatal Health Registry reveals an increased rate, with post-term pregnancies (> 41+0 weeks) representing 34%, the largest group, of the total inductions in BC.
Data from the Registry during 2014/15 reported these overall rates from local hospitals: BC Women’s Hospital: 22.1%, St. Paul’s Hospital 26.2%, Burnaby Hospital 20.4% and Lion’s Gate Hospital 19.3%. Current rates may be higher since the 2015 report. Richmond General Hospital during that time was dedicated to lowering their induction rate and it was at 17.7%. This also reflected a lower cesarean rate at 15.7% compared to higher Cesarean rates at the other hospitals. More on the connection between induction and cesarean in blog post Part Two. What are the current rates as we enter 2022?
THE WHAT: Induction of labour is the artificial initiation of contractions before spontaneous onset of labour to deliver the fetus within 24-48 hours. The goal of induction is to get the uterus to begin to contract, making the body go into labour, in order to vaginally birth the baby. When undertaken for appropriate reasons, and by appropriate methods, induction is useful and benefits both mothers and newborns. There are numerous reasons that induction of labour is recommended, and as we explore in Part Two, we will see that not all, are in fact, evidence based, and/or some research findings are contradictory.
First, it’s necessary that the cervix be ‘favourable’, meaning that it is softening, thinning, shortening and somewhat opening so that induction will be successful, resulting in a vaginal birth. For the purposes of induction, the ‘Bishop Score’ is used to assess if the cervix is favourable to determine the likelihood of success and to select the appropriate method of induction. Bishop Score Calculator for Induction | babyMed.com
It’s crucial that the cervix be favourable, because if not, often further methods might not work and induction fails. Not due to the woman’s body being unable to give birth, but that the induction methods didn’t work, and/or complications arose during the induction process requiring further interventions, including surgery.
There are two main medication options used to help the cervix be ready for the next step in the induction procedure. Using medications with hormone-like substances called prostaglandins, both work to act on softening ‘ripening’ the cervix, much like how male semen works. Each has their pros and cons. Both have similar effects.
CERVIDIL: Cervidil (Dinoprostone): Uses, Dosage, Side Effects, Interactions, Warning
PROSTAGLANDIN GEL: Vaginal prostaglandin (PGE2 and PGF2a) for induction of labour at term | Cochrane
The use of cervidil or prostaglandin gel can cause contractions to occur, but might not always bring about labour. Cervidil, inserted once into the vagina, close to the cervix, is released over a 24 hour period, unlike prostaglandin gel. The gel is inserted into the vagina where it can take its effect on the cervix. The gel can be given 3 times, 6 hours apart. More than one application may be required. Women can experience intense contractions, perhaps lose sleep for a night and then move into chemical induction. Sometimes these medications are successful on their own to tip the body into labour, without the need for further induction medications.
A third option for getting the cervix favourable is the foley bulb catheter. It’s a mechanical means to change the state of the cervix in preparation for chemical induction. What Is a Foley Bulb Induction?
As well, a procedure called ‘sweeping the membranes’ may be suggested/done. What is a stretch and sweep? This is part of an induction process. It may be offered by a care provider as early as 39 weeks gestation. This procedure has been described as a rough cervical check.
‘Membrane sweeping may be effective in achieving a spontaneous onset of labour, but the evidence for this was of low certainty. When compared to expectant management, it potentially reduces the incidence of formal induction of labour. Questions remain as to whether there is an optimal number of membrane sweeps and timings and gestation of these to facilitate induction of labour’. Membrane sweeping for induction of labour
If/once the cervix is favourable, induction proceeds straight to the use of Pitocin (synthetic version of the pregnancy hormone oxytocin), administered via an IV. This medication causes the uterus to contract. Pitocin is given in a hospital setting along with continuous fetal monitoring.
Pitocin causes very strong and frequent contractions, earlier on than physiologic labour, and often leads to requests for pain medications, particularly epidurals, which can add further risks. More on this in Part Two. Along with Pitocin, often the care provider will artificially rupture the membranes (A.R.O.M.), in theory to help speed up the process. A.R.O.M. is an irreversible procedure. Breaking Your Water to Induce or Augment Labor
Bear in mind that induction of labour is very different than normal physiologic labour. To understand how normal physiologic birth works in terms of the hormones involved and their role in initiating spontaneous onset of labour, read here: Hormonal Physiology of Childbearing: Evidence and Implications for Women, Babies, and Maternity Care
The time for the entire induction process may vary, but can take up to 2-3 days, including cervical ripening. Sometimes women go home while waiting for labour to begin, returning to the hospital for a second application, or to begin the next step in the induction process - the use of Pitocin. That part can still take a number of hours, depending on how the dilation phase goes, followed by pushing and birth of the baby. If pain medications are used, ie. an epidural, that will add time to the process. Pushing time may be longer too. If progress is slow, or if the cervix is failing to open with an effective, strong contraction pattern, at some point the care provider will discuss cesarean. Sometimes despite all efforts, the body and baby just aren’t ready. This is termed ‘failed induction’.
Part Two (THE EVIDENCE FOR THE WHY, RISKS & BENEFITS) will follow in a week. It will examine when induction is medically indicated, and when it’s recommended, yet evidence is contradictory/questionable. It will look at how one makes an informed decision. Weighing out the pros and cons to give informed consent or refusal. Please keep an eye out for it.