PONE-D-20-09934

Preterm birth and secondhand smoking during pregnancy: a case–control study from Vietnam

PLOS ONE

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Reviewer #1: Partly

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Reviewer #1: Yes

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Reviewer #1: Yes

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Reviewer #1: Yes

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Reviewer #1: This manuscript by Rang et al addresses an important theme of the effect of secondhand smoking on preterm delivery. There have been several comprehensive articles addressing a parallel theme that reported higher incidence of preterm birth in women exposed to secondhand smoking. The authors of this manuscript confirm earlier findings and suggest that this happens to be true in Vietnamese population. The study uses a sizeable cohort but lacks some rigorous protocols that should have been used and described to strengthen the study.

Major comments:

1. The authors should use some of the rigorous tools that have been described in a similar study by Ashford et al (The effects of prenatal secondhand smoke exposure on preterm birth and neonatal outcomes. J Obstet Neonatal Nurs. 2010; 39:525-535).

2. How did the authors confirm exposure to secondhand smoking? Was it solely based on questionnaire or was a maternal hair nicotine estimation performed on subjects and controls? Such a statement or description is not provided. Without such a quantification of maternal hair nicotine, it is hard to base the authors’ conclusions on verbal or written answers.

3. Were the pregnant women asked about the exposure to smoking prior to or after delivery? It is possible that the women looked for a reason for their preterm deliveries if they were asked after delivery.

4. Did the authors compare the incidence of preterm birth between women with active smoking and women with secondhand exposure? This is very important because this has not been studied.

5. Results: If the reviewer understands it clearly, 67.4% women with preterm birth revealed that they were exposed to secondhand smoke compared to 51% with term pregnancy. This means 51% women with term pregnancy also were exposed. Since 51% exposed women experienced term pregnancy, there must be a second confounding factor in women with preterm birth. Can the authors elaborate on this issue?

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Reviewer #1: No

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Preterm birth and secondhand smoking during pregnancy: a case–control study from Vietnam

PONE-D-20-09934R1

Dear Dr. Nguyen,

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

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Kind regards,

Cheryl S. Rosenfeld, DVM, PhD

Section Editor

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Additional Editor Comments (optional):

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 authors describe a retrospective case-control study investigating the potential influence of SHS on preterm birth rates in a cohort of Vietnamese women. This is a resubmission that addressed the comments of the previous review. The queries previously raised have been addressed.

A few issues could have been discussed in the discussion:

Does paternal cigarette somking affect sperm quality and DNA and therefore pregnancy outcome including risk of preterm birth? For instance Bodi et al 2019 Reproductive Toxicology 87:11-20 report the influence of paternal alcohol intake on fetal growth restriction and a comment regarding this potential confounder would have been relevant: preterm delivery may be attributable to the direct effect of paternal sperm changes from smoking on embryo quality and pregnancy duration rather than SHS.

It is not stated whether smokers within the household smoked in the house or outside.

Table 2 will benefit from a more detailed title - state that the table relates to preterm delivery before 37 weeks.

The limitations should have emphasised that the questionnaires were administered after delivery and therefore bias cannot be excluded.

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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.

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Reviewer #2: No