Reviewer’s report
Title: 
Changes in physical activity across pregnancy among Chinese women: a
longitudinal cohort study
Version: 
0 
Date: 
17 Jul 2020
Reviewer: 
Joellen Wilbur
Reviewer's report:
PThis is a well-written paper addressing several gaps in prior studies of
determinants of PA, 
namely the lack of longitudinal work. The large sample size
showing representation of women across China is a strength. Missing is attention
to a lot of detail 
which is needed to get a complete understanding particularly of
the study methods. 
Background:
* Provide what is known about meeting PA recommendations among women of
child bearing age in China.
* Line 65: not clear if this is addressing all women in general or PA during
pregnancy.
* Need to clearly identify the determinants of PA that will be included and why.
Methods
* Need more information on how participants were recruited.
* Line 100: specify if multiple pregnancy and miscarriage refer to having a prior
history of either
* Need more description on the areas of China from which the participants were
recruited. This will provide some background on how they differ.
* Need a consort sheet showing how many women were screened for
participation and more detail on who did not participate: e.g. Not interested,
could not remember PA. Also include how many had 2 data points. End with
how many completed one data point and how many completed both time points
with what is known about why some women came only once. 
* It would help to have a measures section and include population characteristic
(demographic, pregnancy related and health related measures) and the PA
measure in that section. Pregnancy plan is not defined. It appears it may refer to
whether the pregnancy was planned or not. Also supply more information on all
of the measures of 
population characteristics. Need to be specific about what the
health related measures include. The specific 
measures 
for smoking and drinking
are needed.
* Lines 104-107: These lines include some results, 
in results give weeks
gestation at first visit mean and range
* Somewhere the time frame sent for late pregnancy assessments needs to be
identified.
* Needs a procedures section. 
Results
* Note if those women who did not complete the 2nd time point differed on
demographics from those who did
* Suggest a population characteristics table with totals and by area in China
noting any differences
* In descriptive give mean and range for data collection points. 
Discussion
* Need more on why this population from China would increase PA during
pregnancy which is vastly different from studies with other groups.
* What is it about a lower income area lifestyle that may contribute to more
physical activity. Description of the areas of China in methods may help with
that. 
* Few determinants of PA are explored in this study 
but this is touched on in the
limitations section.
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Yes
Are the methods appropriate and well described?
If not, please specify what is
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No
Does the work include the necessary controls?
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Yes
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Yes
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I recommend additional statistical review
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Acceptable
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