Sir,

We would like to thank Scamell and colleagues for their letter in response to our paper describing the results of the Obstetric Anal Sphincter Injury Care Bundle (OASI-CB) evaluation (1,2). We have previously addressed most of the points raised in our response to an earlier critical review of the OASI-CB by two of the signatories of this letter (3).

First, Scamell and colleagues indicate that they are disappointed in the quality of the evidence that supports the components of the OASI-CB. We feel that this criticism is misdirected, because the OASI-CB project was initiated in response to this lack of high-quality evidence. We developed a care bundle and we performed a multicentre study, which produced evidence of its positive effect.

A second criticism expressed by the authors is that the OASI-CB does not include warm compresses. We have previously acknowledged the evidence that warm compresses reduce the risk of OASI (3). They were not included as a standardised component of the OASI-CB partly because of variation in availability and use (4), and partly because of clinical practicalities such as the feasibility of safely heating/reheating compresses. However, we do encourage the more widespread use of warm compresses because they would further improve the prevention already provided by the OASI-CB.

A third concern raised by the authors is that the OASI-CB has only a small effect: a reduction in the OASI rates from 3.3 to 3.0%. As we explained in our article, this reported reduction is very likely to be an underestimate of the true effect of the OASI-CB, given that the OASI-CB also requires a careful check of the perineum following birth for the immediate detection of OASI. Therefore, we emphatically reject the suggestion that our results could be explained by ascertainment bias.

Last, the authors suggest that we did not consider women's experiences and the acceptability of the OASI-CB. Women were–and still are–at the very heart of the development, evaluation and implementation of the care bundle (2). For example, women told us that they experienced a hands-on approach protecting the perineum as very positive and that good communication with the midwife was key to a calm birth (5).

We are now performing the OASI2 study that evaluates the sustainability of the OASI-CB and its implementation in a wider group of units (www.rcog.org.uk/oasi2). Based on multi-stakeholder discussions and lessons learned from the original OASI-CB project (6), we updated the OASI-CB manual and antenatal discussion guide and improved our training materials. For example, the antenatal discussion guide now also includes antenatal perineal massage, birth position, importance of a slow birth and the use of warm compresses as discussion points alongside the OASI-CB elements. In OASI2, we will also explore women's perspectives further via a large-scale survey.

We would like to reiterate that women's health and a positive birth experience are at the centre of the OASI-CB. Our article presents evidence of the effectiveness of the OASI-CB. It is this evidence that, together with our commitment to support women and clinicians, will empower women to make informed choices about whether or not they want the OASI-CB as part of their birth plan.