PONE-D-21-14641

Association between early gestation passive smoke exposure and neonatal size among self-reported non-smoking women by race/ethnicity: a cohort study

PLOS ONE

Dear Dr. Grantz,

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 the points raised during the review process.

This study is well-written and interesting.  However, I do agree with the reviewers' request for more details in the methods section (i.e., about the biomarkers).  Similar to Reviewer 2, I also found the figures difficult to follow and, additionally, am concerned about the color scheme being sensitive to color-blind readers.

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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: Yes

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: * in your abstract, you mentioned that you measures weight, 10 non-skeletal and 2-skeletal anthropometric measurements, but in the main manuscript (table 1) and supplemental data (S2 &S3), I could only find 8-non skeletal anthropometric measures (MUAC, C, MUHC, AC, TC, AFC, ATC, % Fat mass). Could you explain?

*in the methods section, how did you determine the cut off points for cotinine and nicotine? Could you explain explicitly in the methods section?

* in table 1, the age was significantly differed between both group, but i did not see any adjustment in the results section. Why? the same question also apply to marital status and health insurance.

* in the first paragraph of discussion you mentioned that "cotinine was positively associated with BW and all of non skeletal measures (...) in non hispanic white women......". But this result only consistent for Subscapular, triceps, and abdominal flank circumference, the other measures were not consistent because the 95% CIs included null value. I would suggest to revised this statement because this statement can be misleading.

Reviewer #2: This study aimed to examine the interaction between maternal exposure to secondhand smoke during pregnancy and maternal race/ethnicity on neonatal anthropometric measures. The authors observed that the associations between cotinine concentration and infant weight differed by race/ethnicity- where offspring born to exposed (as opposed to unexposed) White or Hispanic women were larger at birth whereas offspring born to exposed (as opposed to unexposed) Black or Asian women were smaller at birth. Other findings from the study consistently showed systematically smaller offspring born to exposed (as opposed to unexposed) Black or Asian women. The strengths of this study include the large sample size, the use of an ethnically diverse population, and the use of biomarkers to assess exposure to secondhand smoke. found that the secondhand smoke-birth weight association varies by race/ethnicity. Overall, this was a nicely written paper and the findings are very interesting. I have a few comments/questions for the authors as follows:

Consistency in capitalization of Black and White participants. (The authors switch to lowercase in the discussion).

Abstract, lines 12-15: The reference group here is unexposed in the same racial/ethnic group, correct? Please clarify.

Introduction, line 26: What is viz.?

Line 36: The authors might want to clarify that nicotine and cotinine are biomarkers of active AND passive smoking.

Lines 48-29: “This cohort presumably allows for the assessment of passive cigarette smoking exposure in relation to neonatal anthropometry.” I am not sure what this statement means.

Lines 114-117 “Because it is a more stable biomarker and small cell size/low power for analyses using biomarker categorizations, we focused our main analysis on cotinine concentration, with other exposure variables reported to verify consistency across biomarkers and biomarker categorizations.” A few suggestions: 1) include a citation for the improved “stability” of cotinine versus nicotine and 2) clarify what you mean by “small cell size/low power for analyses” (do the authors mean that there was less sparse cells for cotinine?)

Methods: Did the authors consider adjusting for gestational age at birth or restricting the analyses to term births? Some published studies have restricted to term delivery by analyses or by design. (e.g. https://www.nature.com/articles/srep24987). The results may not change, but this stuck out to me as an important consideration.

Table 1: I do believe the rows are flipped for preterm births.

Figures: Would tables be a better way to present the information? The same information presented in tables with bolded numbers (to denote 95% confidence interval not crossing the null) might be easier to read and easier on the eyes. This is my opinion though so I will defer to the editor.

Discussion:

The authors seem to focus on the finding that secondhand smoke is associated with smaller infant size among offspring born to exposed (as compared to unexposed) non-Hispanic Black and Asian women. This is consistent with the literature, which suggests that secondhand/passive smoking in pregnancy is associated with either no change or a slight decrease in birth weight (e.g. https://pubmed.ncbi.nlm.nih.gov/3752056/). So, the finding that infant size is larger among offspring born to exposed (as compared to unexposed) White and Hispanic women is quite surprising. The authors could briefly discuss why this might be, as I think this is a tremendously novel finding from this study.

The authors speculate about the mechanisms for the smaller infant size observed in offspring of Black women, but not Asian women. It would be useful to briefly discuss the underlying mechanisms for smaller infant size among Asian women. In particular, percent fat mass appears to be a lot lower. This may be particularly important because percent fat mass may be a surrogate for maternal exposures in pregnancy as well as childhood obesity. https://pubmed.ncbi.nlm.nih.gov/32796097/

Limitations: There are many potential confounders that are not measured/adjusted for that could have a huge impact on infant size at birth. In particular, gestational weight gain and maternal diet are very closely related to the exposure and outcome, and vary considerably within racial/ethnic groups. I think the authors should think carefully about how these variables could impact their analyses and perhaps soften some of the statements in the discussion. I do wonder if some of these racial/ethnic differences would weaken or disappear if the analyses had adjusted for these potential confounders.

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Reviewer #1: Yes: Frida Soesanti

Reviewer #2: No

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Association between early gestation passive smoke exposure and neonatal size among self-reported non-smoking women by race/ethnicity: a cohort study

PONE-D-21-14641R1

Dear Dr. Grantz,

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.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Sze Yan Liu, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

The authors did an excellent job addressing concerns from earlier submissions. 

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 #1: All comments have been addressed

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 #1: Yes

Reviewer #2: Yes

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

Reviewer #1: Yes

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 #1: Yes

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 #1: Yes

Reviewer #2: Yes

**********

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 #1: All of my concerns have been well addressed by the authors. This manuscript is very well written and the conclusion was drawn based on robust data and appropriate statistical analysis.

Reviewer #2: Thank you for the opportunity to review the revised submission. I am impressed with the author's careful responses and attention to detail in their statistical analysis. Additionally, the discussion was very interesting to read. I appreciated that the authors outlined some very plausible potential mechanisms to explain the somewhat surprising result that increased cotinine concentrations were associated with increases in anthropometric measures in non-Hispanic White (and Hispanic women, to a lesser extent).

Overall, this was a pleasure to read. I believe this manuscript is ready for 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 #1: Yes: Frida Soesanti

Reviewer #2: No