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PONE-D-20-03397

Changing risk factors for placental abruption: a case crossover study using routinely collected data from Finland, Malta and Aberdeen

PLOS ONE

Dear Dr Bhattacharya,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses ALL the points raised during the review process.

SPECIFIC ACADEMIC EDITOR COMMENTS: Your manuscript was reviewed by two experts in the field. Although interest was found in your study, there were several major comments and questions that arose during the review process. These include, but are not limited to the need to clarify the novelty of this specific study, because the majority of these findings are already known. Furthermore, there were requests for additional data about birth weight, IUGR, week of delivery, mode of delivery, patients with induced labor, and specifics about IVF treatment and alcohol use. And the question was raised about how placental abruption was diagnosed in the cases of placenta previa.

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Frank T. Spradley

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Changing risk factors for placental abruption: a case crossover study using routinely collected data from Finland, Malta and Aberdeen.

This study is a case-crossover study design with records of the two first pregnancies from women who had PA in one pregnancy and not the other.

Cases were pregnancies with abruption and matched controls were pregnancies without abruption in the same woman. A total of 2991 women were included in their study.

The study is well written, and I command the authors for the study design and size of the cohort.

However, I have concerns about the importance and novelty of the data since all risk factors statistically significant in the study are well known in the literature.

Furthermore, in my opinion, some important data is lacking which could influence the results and for example: *Week of delivery, Induction of labor

*Mode of delivery- mainly important in the second pregnancy after PA. Since previous PA is a strong and well known it is possible that an elective Cesarean delivery was performed in an earlier week and affected the occurrence of PA in the coming pregnancy. I ask the authors to add this data if possible.

* IVF treatment and alcohol use- As the authors mentioned in the limitations of the study.

Regarding placenta previa as a risk factor for placenta abruption, how was the diagnosis of abruption done in the cases of placenta previa? Since bleeding is a common symptom did data regarding placenta pathology is present in the registry?

Reviewer #2: I really enjoyed reading your paper. It is refreshing, well designed and well written. I have some minor comments:

1. Is it any reason that you did not include birth weight or more specifically intrauterine growth restriction (IUGR) in your data?

2. Could you please provide the numbers and percentages in your tables as well as OR, CI and P-values?

3. I think you should categorize maternal age into only 3 categories: <20, 20-35 and >35. This is only a suggestion; you don’t have to do that.

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Reviewer #1: No

Reviewer #2: Yes: Elham Baghestan

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Changing risk factors for placental abruption: a case crossover study using routinely collected data from Finland, Malta and Aberdeen

PONE-D-20-03397R1

Dear Dr. Bhattacharya,

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.

Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication.

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With kind regards,

Frank T. Spradley

Academic Editor

PLOS ONE

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: The autors have responded adequately to my comments. I have no further comments and wish you luck with the publication.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: Yes: Elham Baghestan