Does oxytocin use affect the severity of OASI symptoms?

A new study has shown that a number of factors may influence the severity of anal incontinence after obstetric anal sphincter injury and its authors suggest that, “modifiable factors such as use of forceps and oxytocin should be taken into consideration in clinical practice” (Joris et al 2019).

Obstetric anal sphincter injury (OASI) is a severe complication of childbirth. Its incidence is increasing and some people are concerned that this is partly due to increased medicalisation of childbirth. Quite a bit of research has already been done to look at risk factors for OASI (although it has to be said that some of these studies are more thoughtful and woman-centred than others) but we don’t know much about whether there are factors that can affect the severity of the symptoms that women experience after OASI.

Joris et al (2019) set out to answer that question and looked at the maternity records of 11,483 women in order to identify those who had experienced OASI (a total of 88 women) and to compare them with the wider population of the women who birthed in that area. The authors found that, “The only statistically significant differences between symptomatic and asymptomatic women were age (p = 0.02), body mass index (p = 0.04) and the use of forceps (p = 0.04). Women with more severe symptoms were more likely to have received oxytocin during the second stage of labor (p = 0.03) and had shorter delivery to follow-up interval (p = 0.008).” (Joris et al 2019).

The study is retrospective and the authors, as is often the case, acknowledge that “larger prospective studies are needed to examine this possible correlation” (Joris et al 2019). but they also note that their findings are similar to those in other studies.

We don’t know why older women have a higher chance of more severe symptoms or why larger women are less affected, although the authors speculate about this. We do know that both of these groups of women are often treated more poorly by care providers and exposed to more intervention than other women, so the issues are complex. The authors note that the finding about delivery to follow-up interval is something that needs to be further considered by clinicians, and it’s not a straightforward finding that leads to a simple recommendation. Quite a few women find that their symptoms improve with time, so it’s inevitable that those seen later will have fewer symptoms. And with the best will in the world, there is probably always going to be some variation in the time span between when a woman gives birth and when she is seen again to check how her body and any injury is healing. This isn’t only because of pressure on hospitals and clinicians, but because appointments are sometimes adjusted around holidays and a woman’s own availability.

Sara Wickham’s bestselling book explains the process of induction of labour and shares information from research studies, debates and women’s, midwives’ and doctors’ experiences to help women and families become more informed and make the decision that is right for them.

The finding that the use of oxytocin (which is a key component of induction of labour) was more common in women who had more severe symptoms following anal sphincter injury is an important piece of information which women should be able to take into account in their decision-making. More and more women are being offered induction of labour, often with little or no evidence to support this recommendation. This issue is even more pertinent for older women, who already have a higher chance of having an OASI and who are among the groups of women who are now routinely offered induction of labour in some areas of the world.

Joris F, Hoesli I, Kind A et al (2019). Obstetrical and epidemiological factors influence the severity of anal incontinence after obstetric anal sphincter injury. BMC Pregnancy and Childbirth 19:94 https://doi.org/10.1186/s12884-019-2238-2

The Research

Background: Obstetric anal sphincter injury (OASI) is one of the most severe obstetrical complications. Although risk factors for OASI have been identified, little is known about various parameters that can influence symptoms’ severity. The aim of this study is to explore whether obstetrical and epidemiological factors can have an effect on the severity of symptoms after OASI.

Methods: 11.483 deliveries between January 2010 and December 2014 were reviewed, and data from 88 women with OASI are presented.

Results: The only statistically significant differences between symptomatic and asymptomatic women were age (p = 0.02), body mass index (p = 0.04) and the use of forceps (p = 0.04). Women with more severe symptoms were more likely to have received oxytocin during the second stage of labor (p = 0.03) and had shorter delivery to follow-up interval (p = 0.008).

Conclusions: Modifiable factors such as use of forceps and oxytocin should be taken into consideration in clinical practice.