Reviewer’s report
Title: 
Comparison of levonorgestrel level and creamatocrit in milk following
immediate vs. delayed postpartum placement of the levonorgestrel IUD
Version: 
0 
Date: 
25 Jul 2020
Reviewer's report:
This is a useful paper, the paper objectives are exploratory, however it would
help to understand more on the design and the rationale behind the sample size
they used. 
Explain the rationale for use of non-parametric methods for estimation (instead
of the parametric ones)
How were differences between the two levels of the exposures (or groups as you
call them) was taken into account in reporting the outcome estimates, 
Discussion should explain the role of different sources of biases including the
selection bias.
Additional comments below:
Line 66: Study design has to be clearly labelled. Looks like prospective
(observational) cohort study, with immediate or delayed IUD placement as the
main exposure.
Line 86: Sample: Flowchart 
(inclusion, exclusions) that gave result to the
resulting sample used for the sub-study should be included or at least some
explanation has to be provided.
Line 90: What was the rationale for selecting 12 pairs or was it adhoc, why
paired? Provide extra information on the sample size assumptions used. 
Also
explain how the pairing was done from the initial sample of 259 subjects.
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
Yes
Are the methods sufficiently described to allow the study to be repeated?
No
Is the use of statistics and treatment of uncertainties appropriate?
No
Is the presentation of the work clear?
No
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes