Dear Dr Khalil,

Thank you for submitting your manuscript entitled "Impact of Point of Care Ultrasound and routine third trimester ultrasound on undiagnosed breech presentation and perinatal outcomes" for consideration by PLOS Medicine.

Your manuscript has now been evaluated by the PLOS Medicine editorial staff and I am writing to let you know that we would like to send your submission out for external peer review.

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Feel free to email us at plosmedicine@plos.org if you have any queries relating to your submission.

Kind regards,

Beryne Odeny

PLOS Medicine

Dear Dr. Khalil,

Thank you very much for submitting your manuscript "Impact of Point of Care Ultrasound and routine third trimester ultrasound on undiagnosed breech presentation and perinatal outcomes" (PMEDICINE-D-22-02818R1) for consideration at PLOS Medicine.

Your paper was evaluated by a senior editor and discussed among all the editors here. It was also sent to independent reviewers, including a statistical reviewer. The reviews are appended at the bottom of this email and any accompanying reviewer attachments can be seen via the link below:

[LINK]

In light of these reviews, I am afraid that we will not be able to accept the manuscript for publication in the journal in its current form, but we would like to consider a revised version that addresses the reviewers' and editors' comments. Obviously we cannot make any decision about publication until we have seen the revised manuscript and your response, and we plan to seek re-review by one or more of the reviewers.

In revising the manuscript for further consideration, your revisions should address the specific points made by each reviewer and the editors. Please also check the guidelines for revised papers at http://journals.plos.org/plosmedicine/s/revising-your-manuscript for any that apply to your paper. In your rebuttal letter you should indicate your response to the reviewers' and editors' comments, the changes you have made in the manuscript, and include either an excerpt of the revised text or the location (eg: page and line number) where each change can be found. Please submit a clean version of the paper as the main article file; a version with changes marked should be uploaded as a marked up manuscript.

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We ask every co-author listed on the manuscript to fill in a contributing author statement, making sure to declare all competing interests. If any of the co-authors have not filled in the statement, we will remind them to do so when the paper is revised. If all statements are not completed in a timely fashion this could hold up the re-review process. If new competing interests are declared later in the revision process, this may also hold up the submission. Should there be a problem getting one of your co-authors to fill in a statement we will be in contact. YOU MUST NOT ADD OR REMOVE AUTHORS UNLESS YOU HAVE ALERTED THE EDITOR HANDLING THE MANUSCRIPT TO THE CHANGE AND THEY SPECIFICALLY HAVE AGREED TO IT. You can see our competing interests policy here: http://journals.plos.org/plosmedicine/s/competing-interests.

Please use the following link to submit the revised manuscript:

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Your article can be found in the "Submissions Needing Revision" folder.

To enhance the reproducibility of your results, we recommend that you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. Additionally, PLOS ONE offers an option to publish peer-reviewed clinical study protocols. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols

Please ensure that the paper adheres to the PLOS Data Availability Policy (see http://journals.plos.org/plosmedicine/s/data-availability), which requires that all data underlying the study's findings be provided in a repository or as Supporting Information. For data residing with a third party, authors are required to provide instructions with contact information for obtaining the data. PLOS journals do not allow statements supported by "data not shown" or "unpublished results." For such statements, authors must provide supporting data or cite public sources that include it.

We look forward to receiving your revised manuscript.

Sincerely,

Pippa

Philippa Dodd MBBS MRCP PhD

PLOS Medicine

plosmedicine.org

-----------------------------------------------------------

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GENERAL

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Table 2 – suggest removing the second header row between the cohorts – I appreciate that this is to detail the difference in n numbers across the different cohorts but a lot of information is repeated, perhaps unnecessarily, to satisfy that specific requirement. Please revise the presentation of this table to improve accessibility to the reader

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REFERENCES

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Comments from the reviewers:

Reviewer #1:

This study assesses the 'impact' of a universal third trimester ultrasound on breech presentation. It concludes, using 2 'before and after' cohorts from 2 different units introducing 2 different types of 3rd trimester scans, that undiagnosed breech presentation is significantly reduced, that the incidence of breech presentation stays the same, and that the incidence of low Apgar scores is significantly reduced.

The first two findings subsequent to a universal scan have been shown before in a single unit cohort previously published in Plos Medicine (salim et al) to which this papers refers, and from which the analysis takes 'informative priors'. The reduction in undiagnosed breech has been shown too, albeit in nulliparous women in research setting, also published in this journal (Wastlund et al) (also cited in this paper). The reduction in Apgar scores was not 'significant' in the Salim study, but with this, it is. That this is so when more data is used should not be considered a surprise: antenatal diagnosis allows more caesarean sections (I note overall numbers not changed but no analysis is specifically presented on cs rates for breech babies- see point below) for breech babies: caesarean sections for breech improve short term outcomes and, according to the term breech trial and huge cohorts from the Netherlands, death.

The methodology requires scrutiny by a statistical reviewer and I am not one. This means that I do not fully understand- and apologise for this- how, for instance, despite my point above, the paper concludes that 5 min Apgar scores <7 are reduced, when using a simple chi-squared test amalgamating numbers from Salim et al and from this paper I calculate a chi-square statistic of 2.2251; p= 0.14: i.e. still 'not significant' in lay terms.

Although I have outlined that antenatal diagnosis will have benefits, the abstract suggests to the uninitiated reader like me that the paper actually demonstrates a reduction in HIE: 'There was moderate to high probability (posterior probability: 89.5% and 85.1%, respectively) of a reduction of hypoxic ischemic encephalopathy (HIE) (RR: 0.23, 95% CI: 0.14-0.38)… '. Yet this is not the case, the numbers simply being inadequate for this: table 2 shows just 2 before and 1 after the scan was introduced. Without fully understanding the methodology this seems disingenuous.

Another issue with this paper is the loss of the 'real world' (what happens in a unit when…) benefits to an impact/ 'changes subsequent to' paper. This is because of there being 2 different units, the intervention was slightly different (proper scan and presentation scan) and ECV was not documented/ discussed. This means it potentially has less relevance for a 'unit' and is more of a 'poor man's' (person's) RCT.

I remain surprised at all the research into a universal 'presentation only' scan. I think we know the answer- most breeches become diagnosed. This affects only about 5% of the population. Given the (accepted) benefits of elective caesarean for breech babies have probably been exaggerated (RCOG Greentop Guideline 2017) the overall effect on pregnancy safety is going to be small. And of course performing caesarean sections on all breech babies leads to a loss of skills and therefore probably increased risk for the small (in this study and that of Salim et al) but persistent breeches that still slip through. I make this comment because this pertains to the relevance of this- and other studies such as Salim et al- for overall pregnancy safety; in contrast, a 'proper' scan that could affect the other 95% as well is the one that needs the research attention.

I would like to see data on how many third trimester scans were actually performed- before and after.

No table data on gestation at birth or mode of birth is presented for the babies who were actually breech.

The lack of ECV data is acknowledged as a limitation but inadequately so. The Salim study they quote was not a 'research setting' and its data and discussion of ECV was comprehensive. This lack also causes the problem below:

By looking at outcomes in breech babies only at birth (this is not 100% clear at least in the table) an assumption is being made that the universal scan could not alter outcomes for other babies. It could- not just for babies that were breech at birth (eg ECV could be performed which could lead to not being breech and therefore not being included in the outcomes, or some other benefit, or indeed, theoretically, harm). Salim et al 'get around' this by including all babies diagnosed as breech. The method employed by Salim et al has drawbacks too (it did not include those undiagnosed before the universal scan), but the method used here should at least be justified and discussed as a limitation.

The pretty Figs 1 and 2 add little useful information bar perhaps demonstrating causality better re undiagnosed breech presentation- but this should be obvious by now.

In spite of my largely minor reservations, if this stands up to statistical review, this paper cleverly demonstrates one of the benefits to spreading the use of ultrasound in pregnancy.

Reviewer #2: This was a clinically meaningful study, well-written and generally easy to follow. The conclusions are clear and compelling. The role of midwives in delivering POCUS is especially unique and helpful given the potential for this model to be introduced more widely in clinical settings globally. The use of probabilities in the results is confusing to follow, the risk reduction is much easier to understand clinically, however these results are presented in the context of the analysis conducted.

The only suggested changes relate to the interpretation of findings. In the Discussion, I think it is important to clearly mention a) the role of mode of birth in the risk of neonatal adverse outcomes (ie what proportion of women with breech babies proceeded to CS and thus what was the impact of MOB on outcomes, if any, assuming that CS eliminates most of the breech-related risks of vaginal breech birth) and b) the role of parity or the proportion of multiparous women in each group.

Reviewer #3: 1. Line 120-122. "For both centers, pregnancies were grouped according to whether they received routine third-trimester scan (SGH) or POCUS (MNUH)." For the analysis, did the author include all the pregnancies or just include those received routine third-trimester scan at SGH or PROCUS at MNUH?

2. What's the reason for only including SGH cohort was in Table 1/Figure 1 ? How about the NNUH cohort?

3. As the log-binomial regression is used to analyze the association between undiagnosed breach presentation at birth and adverse perinatal outcomes, should the outcome be OR (odds ratio) rather than RR (relative risk?)

Reviewer #4: Thanks for allowing me to review your very interesting manuscript. I agree that the data presented show an impressive reduction in the chance of an undiagnosed breech presentation at term after both routine ultrasound screening and POCUS, carried out in two different hospitals. It would, of course, be a more rigorous study design to compare routine antenatal care with both routine ultrasound and POCUS in the same setting, or to have randomised rather than use a before and after design, but based on your data both methods appear to reduce the percentage of breech presentations that are undiagnosed at the start of labour or membrane rupture. I have a few minor points to make which could lead to some minor revisions:

1. I found the phrase 'the rate of undiagnosed breech' a bit confusing as it suggested to me that, for example, 14.2% of babies were presenting in labour as undiagnosed breeches. It might be better to say the 'percentage of all term breech presentations that were undiagnosed was 14.2%.....'

2. The statement that there was no significant change in the rate of vaginal breech birth (and the figures are given of 10 per 10,000, which was reducing to 5 per 10,000 after the scanning interventions) is somewhat surprising given the very significant change (reduction) in the percentage of undiagnosed breech presentations. Are you able to explain that?

3. These data would suggest to me that prior to the intervention most breech babies were born by c/section, so it is then a little hard to understand how such an improvement in perinatal outcome has been achieved. I realise that the outcome data were secondary outcomes but the paper seems to argue that there is a high rate of morbidity/mortality associated with vaginal breech birth, yet the improvement in perinatal outcomes has occurred without much change in the rate. Indeed, given the numbers quoted the numbers of term vaginal births at SGH during the study period would have reduced from about 17 in the pre-ultrasound period to 4 after. To have seen a measurable reduction in the rate of low Apgar scores and rates of HIE would be remarkable, and would imply that outcomes for vaginal breeches were very poor in the pre-ultrasound period. Can you comment further on this?

3. A minor point is that data is a plural noun and is sometimes used as a singular one (e.g. page 172)

4. Finally, I was left uncertain as to whether or not you would advocate a policy of routine ultrasound or POCUS or a hybrid of the two depending on risk? Or do you have plans to compare the two approaches in the same setting?

Any attachments provided with reviews can be seen via the following link:

[LINK]

Dear Dr. Khalil,

Thank you very much for re-submitting your manuscript "Impact of Point of Care Ultrasound and routine third trimester ultrasound on undiagnosed breech presentation and perinatal outcomes: a retrospective study" (PMEDICINE-D-22-02818R2) for review by PLOS Medicine.

I have discussed the paper with my colleagues and the academic editor and it was also seen again by 4 reviewers. I am pleased to say that provided the remaining editorial and production issues are dealt with we are planning to accept the paper for publication in the journal.

The remaining issues that need to be addressed are listed at the end of this email. Any accompanying reviewer attachments can be seen via the link below. Please take these into account before resubmitting your manuscript:

[LINK]

***Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.***

In revising the manuscript for further consideration here, please ensure you address the specific points made by each reviewer and the editors. In your rebuttal letter you should indicate your response to the reviewers' and editors' comments and the changes you have made in the manuscript. Please submit a clean version of the paper as the main article file. A version with changes marked must also be uploaded as a marked up manuscript file.

Please also check the guidelines for revised papers at http://journals.plos.org/plosmedicine/s/revising-your-manuscript for any that apply to your paper. If you haven't already, we ask that you provide a short, non-technical Author Summary of your research to make findings accessible to a wide audience that includes both scientists and non-scientists. The Author Summary should immediately follow the Abstract in your revised manuscript. This text is subject to editorial change and should be distinct from the scientific abstract.

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To enhance the reproducibility of your results, we recommend that you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. Additionally, PLOS ONE offers an option to publish peer-reviewed clinical study protocols. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols

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If you have any questions in the meantime, please contact me or the journal staff on plosmedicine@plos.org.  

We look forward to receiving the revised manuscript by Jan 26 2023 11:59PM.   

Sincerely,

Philippa Dodd, MBBS MRCP PhD

PLOS Medicine

plosmedicine.org

------------------------------------------------------------

Requests from Editors:

GENERAL

Thank you for your detailed and considerate responses to previous editor and reviewer comments. Please see below for further comments that we require you respond to in full.

TITLE

Thank you for revising your title suggest “Impact of Point of Care Ultrasound and routine third trimester ultrasound on undiagnosed breech presentation and perinatal outcomes: an observational multi-centre cohort study” or something similar

ABSTRACT

Thank you for revising your abstract and for including p-values as well as 95% CIs. For each outcome measure reported we request that both p-values and 95% CIs are reported. If not please clearly state the reasons why not, for purposes of transparent data reporting (please remember that when reporting p-values to report as p<0.001 or where higher the exact p-value as p= 0.002, for example).

Suggest reporting as follows – for example, line 59 - (RR: 59 0.29, 95% CI [0.20–0.38], p<0.001) for optimal reader accessibility.

Please note the use of parentheses around the CIs and the absence of the semi-colon. You may wish to consider separating upper and lower limits with commas rather than hyphens (as these can be confused with negative values) but we leave it to your discretion.

Please check and revise throughout, including in the main manuscript text and tables where relevant – please see below also

AUTHOR SUMMARY

Thank you for including an author summary which reads very nicely.

Line 100: we appreciate the explanation of your chosen methodological approach, suggest revising to ensure that the statement is interpretable to the more general reader – some may be unfamiliar with the concept of informative priors, for example

Line 103: “incidence of percentage…” suggest removing of percentage perhaps?

Line 104: suggest quantifying “drastically (a percentage will be adequate here)

Line 113: It would be helpful to elaborate on the reasons why assessing cost-effectiveness is necessary – i.e. for feasibility of implementation on a wider scale

METHODS and RESULTS

Please revise statistical reporting as suggested above

please quantify all reported percentages with numerators and denominators, for example line 271, “(12.9 vs 11.5%, p=0.029)” - please check and amend throughout

Please also report CIs where p-values are reported, if not please clearly state why not, for purposes of transparent data reporting

TABLES

Currently journal requirements stipulate that where 95% CIs are presented, including in tables, that p-values are also reported. Please include p-values but if not in your rebuttal letter, please clearly state the reasons why not, for transparency of data reporting

Table 3.a – suggest removing the SGH cohort row – perhaps a remnant of the previous version

DISCUSSION

Please remove the sub-heading conclusion.

Line 404: given the observational nature of the study suggest tempering the language here slightly, “Our data suggest that a policy….could be effective in…” or something similar, for example

SOCIAL MEDIA

To help us extend the reach of your research, please provide any Twitter handle(s) that would be appropriate to tag, including your own, your co-authors’, your institution, funder, or lab. Please include these in the manuscript submission form when you re-submit your manuscript

Comments from Reviewers:

Reviewer #1: the authors have addressed all points satisfactorily

Reviewer #2: Thank you for your thorough attempts to rectify requested changes. The manuscript has been satisfactorily updated and improved.

Reviewer #3: I appreciate authors' effors in addressing the questions and revising the paper. I have no further comments.

Reviewer #4: Thanks for responding to my previous comments and to those of other reviewers. I have three relatively minor additional points to make about your revised manuscript;

1. Line 50 (Abstract). Can you confirm that the statement 'the rate of breech presentation in labour was consistent across all groups (3-4%)' is correct and does this refer to all births? It seems very high if the usual exclusions of preterm, multiples, congenital anomalies are applied.

2. Line 116 (Introduction). Similarly, is this figure of 3-4% used in the Introduction inclusive of all births, and does it exclude multiple pregnancies?

3. Line 175. I would think that 'Southwest London' is usually written as 'South West London' but as I am not a resident of London I am happy to be corrected.

Any attachments provided with reviews can be seen via the following link:

[LINK]

Dear Dr Khalil, 

On behalf of my colleagues and the Academic Editor, Dr. Anthea C Lindquist, I am pleased to inform you that we have agreed to publish your manuscript "Impact of Point of Care Ultrasound and routine third trimester ultrasound on undiagnosed breech presentation and perinatal outcomes: an observational multi-centre cohort study" (PMEDICINE-D-22-02818R3) in PLOS Medicine.

Prior to publication, on advice of the Academic Editor, whose comments are also included below, we require that you make the following final revisions:

This is an important study with direct clinical impact and will be of great interest to maternity clinicians globally.

The suggested revisions have generally been very appropriately addressed or appropriately rebutted. There are a few remaining issues to address:

Line 103 - wording doesn't make sense, needs to be clarified

Line 222 - 'excluding' should be 'excluded'

Line 226 - 'was' should be 'were' in keeping with the plural nature of data

Line 270-271 - reads as though the GA was the same (39.1 weeks) between groups but still significantly different - needs to be clarified, how can this differ?

Table 2 - mode of birth - needs to include in legend if all 3 breech vaginal birth categories (breech extraction, breech with forceps and spontaneous breech) were mutually exclusive or not? The same babies could all feasibly be included in all groups.

Line 317-318 - 'term' is used twice, only one is necessary

Line 328 - should read 'the first'

Line 331 - should read 'the rarity'

Line 349 - 'was not' should read 'were not' owing to plural data

Line 359-360 - 'term' is used twice, only needed once

Line 371 - remove 'the' from 'the neonatal'

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PRESS

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Thank you again for submitting to PLOS Medicine, it has been a pleasure handling your manuscript. We look forward to publishing your paper. 

Best wishes, 

Pippa

Philippa Dodd, MBBS MRCP PhD 

PLOS Medicine