Review for 10.1186/1471-230X-11-6 (2011)

Reviewer's report
Title:Effect of the mode of delivery on Crohn's disease; results from a
retrospective cohort study
Version: 1Date:22 June 2010
Reviewer: Geir Aamodt
Reviewer's report:
This article is about birth outcomes and progression after birth among women
with Crohn’s disease. Some smaller comments in the first sections, but the
discussion section should be rewritten to include strengths/weaknesses.
Major/minor
Throughout the manuscript: Please report numbers in a consistent way (0.04 not
0,04). Please also report the number of digits consistent. Odds ratio is reported
as 4.57 and 4.6 (page 2 and page 9.
The title should contain information about study period and country.
Abstract:
The same information (period and country) should also be included in the
abstract. In the result part, the different comparisons should also be reported
more precisely: active luminal disease compared to inactive luminal disease,
patients with and without perianal disease etc.
All results should be reported with an associated p-value or confidence interval.
The result concerning mode of delivery among women with or without perianal
disease is difficult to understand and interpret.
Methods:
Please specify the meaning of ‘IBD database’.
Did you exclude women who gave birth at other hospitals (page 5, line 9-10)?
Please include a sentence in the statistical analysis paragraph that you use the
odds ratio and their confidence intervals to study differences between groups.
Results:
Please list the different reasons for exclusions in the text (p7, line 5)
The name of the paragraph “Pregnancy outcome” is misleading. This and the
following paragraphs contain information about active and inactive luminal
disease and their pregnancy outcomes.
Please report p-values when appropriate. Birth weights between women with
active/inactive luminal disease are reported with a p-value in the abstract, but not
in the result section.
Concerning small numbers (page 9): It is not correct to conclude that your results
are not significant due to small numbers. It is better to report your findings and as
a comment tell the reader that the sample size is small.
Discussion:
The discussion is about the two questions raised in Methods section: Is mode of
delivery a risk factor for course of disease and is episiotomy a preventive factor
for perianal disease? In spite of your interesting point concerning confounding by
indication could the first of these questions be analysed using logistic
regression? Outcome variable will be course of disease and explanatory
variables could be mode of declivity and other variables associated with course
of disease (age at onset, age, parity)?
Your results should be reported in the first paragraph of the discussion. You
should also discuss strengths and weaknesses of your study.
Please include a reference at page 11, line 16-19 when you discuss progression
of disease among patients with and without active luminal disease.
Could you include a reference and a short definition of “confounding by
indication”. One choice is Rothman’s book: Epidemiology In introduction (2002),
page 103.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
No competing interests