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: Yi-Hua Chen
Reviewer's report:
Comments for the Author:
This study attempted to investigate whether the mode of delivery affected the
course of Crohn’s disease. Women whose Crohn’s disease was complicated by
perianal disease were further specified and examined. Although the research
question is interesting and clinically relevant, the results provided were mainly
descriptive and were drawn from patients in ONE hospital. Several concerns and
comments are listed below.
1. The sample was drawn from ONE hospital. What is the location of this
hospital? What are the traits of this hospital? And how is the representativeness
of these patients?
2. The authors talked about recall bias in several places. Indeed, recall bias is a
serious concern as these women aged between 18 to 80 years and the median
interval between investigation and delivery is 10 years (maximum of 39 years).
The data provided (with the very detailed questions on IBD, obstetric history,
medication during pregnancy) might be more mixed or less reliable especially for
those who delivered longer time ago or who had more than one child after the
Crohn’s disease. How do authors consider the effects of recall bias on their
findings?
3. Again, as median interval between investigation and delivery is 10 years
(maximum of 39 years), is it possible that the management of the disease and
guidelines of delivery mode selection (e.g., indication for CS) have been
amended in these decades? How could these affect study results?
4. As volunteer bias is a concern, is it possible to compare certain traits (e.g.,
sociodemographics or Crohn’s disease severity) for respondents and
non-respondents in the IBD database?
5. Methods were not clearly described, including
a. How is the Crohn’s disease defined? From physician diagnosis using ICD
codes? Please specify.
b. What are the reliability and validity of the questionnaire? Are these questions
adopted from other study or designed by authors for this study?
c. Who performed the chart review? Any estimation of inter-rater reliability?
6. I am not able to read Figure 1 (not attached along with the manuscript).
7. In Table 3, are the ORs all crude ORs? Is it possible to consider the effects of
potential confounders? Although the results were significant, the confidence
intervals were quite wide (less precision). In addition, small sample size in this
study further restricted the authors to observe significant findings after
stratification.
8. The authors mentioned that “the significant difference in disease progression
between both modes of delivery needs to be interpreted carefully due to a
confounding effect by indication for caesarean section” (Last line, Page 11 to first
two lines, Page 12). Please be more specific on discussing the confounding
effects of CS indication. Please also provide literature citations. And how could
the indication for CS confound the association observed in this study (the
direction of the bias).
9. In this study, 94% were nulliparous at the time of the index pregnancy. Does
this accord with authors’ anticipation? What would authors expect the effects of
parity on the association examined?
10. In the questionnaire, respondents were asked to provide their medication
during pregnancy. What were the effects of medication on Crohn’s disease and
pregnancy outcomes? Is the association examined in this study confounded or
modified by medication use?
11. Study limitations were not clearly stated. Please discuss limitations in one
paragraph.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests.