Reviewer ’s report  
 
Title: Nocturnal finger skin temperature in menstrual cycle trackin g: Ambulatory pilot study 
using a wearable Oura ring  
 
Version: 0 Date: 23 Apr 2019  
 
Reviewer: Helena Kopp Kallner  
 
Reviewer's report:  
Review  
 
This paper is rather well written and describes the use of a ring to measure basal body temperature 
throughout the menstrual cycle. Exactly what this will be used for is not entirely obvious but it seems the 
authors are more interested in health applications that contraception and fertility. The English need to be 
checked but not to a large extent.  
 
Genera l comments  
I miss a discussion on improvements. How could the method be improved?  
Is it really necessary to open the app and download the temperature? Why is this not done automatically?  
With longer registration - would it not be better with a "learning al gorithm" which improves with longer 
registration?  
I also miss a discussion on why women participated? Were they offered anything to participate or did 
they do it "just for fun".  
And finally I miss a discussion on the performance of predicition in relation to existing published apps 
such as the Dot app and Natural Cycles. Even though they are menstruations trackers and contraceptive 
devices - it is still interesting with a discussion why anyone would choose to use this model with the ring 
instead of the exist ing ones  
Lastly this is quite a mathematical paper and I would let someone familiar with correlation statistics and 
algorithms review the paper.  
 
 
 
 
Specific comments  
Line 58 would state the most common premenstrual symptoms here. Such as irritability, ange r or 
depressed mood.  
Line 61 vaginal flow is awkward. Vaginal secretion?  
Line 63 "follow ovulation for". Rewrite - eg The rise in BBT occurs at 1 -3 days post ovulation.  
Line 74 strange sentence  
Line 78 -83 just to be sure I understand. The distal skin temperature rises as CBT decreases?  
line 231 Please justify using the window lengths used. They seem very wide. Would anyone accept +/ - 4 
days? Especially considering the survival of sperm of 6 days.  If it were to be used for contraception eg or 
for identifying the fertile window.  
Line 298 generally good is a bit too subjective. What exactly is meant by good?  
Line 313 -321 would leave out the algorithms that did not perform well.  
Line 343 don't unde rstand. Is this not what has been done. But retrospectively with the dates already 
known beforehand. Why would this differ from what has been done?  
Line 351 it seems that these areas for use are not the most obvious ones and they are hardly mentioned in 
the manuscript at all.  
Line 328. Interesting that you call this limitation - I would call it a strength that it performed so well under 
these more "typical use" conditions.  
 
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
 
Yes 
 
Does the work include the necessary  controls?  
If not, please specify which controls are required in your comments to the authors.  
 
Yes 
 
Are the conclusions drawn adequately supported by the data shown?  
If not, please explain in your comments to the authors.  
 
Yes 
 
 
Are you able to assess any stat istics in the manus cript or would you recommend an 
additional statistical review?  
If an additional statistical review is recommended, please speci fy what aspects require further 
assessment in your comments to the editors.  
 
I recommend additi onal statistical review  
 
Quality of written English  
Please indicate the quality of language in the manuscript:  
 
Needs some language corrections before being published  
 
Declaration of competing interests  
Please complete a declaration of competing interests, considering the following questions:  
 
1. Have you in the past five years received reimbursements, f ees, funding, or salary from an 
organisation that may in any way gain or lose financial ly from the publication of this 
manuscript, either now or in the future?  
 
2. Do you hold any stocks or shares  in an organisation t hat may in any way gain or lose 
financially from the publication of this manuscript, either now or in the future?  
 
3. Do you hold or are you currently applying for any patents  relating to the content of the 
manuscript?  
 
4. Have you recei ved reimbursements, fees, funding, or salary from an organization that 
holds or has applied for patents relating to the content of the manuscript?  
 
5. Do you have any other financial competing interests?  
 
6. Do you have any non -financial competing interests in relation to this paper?  
 
If you can answer no to all of the above, write 'I declare that I have  no competin g interests' 
below. If your reply is yes to any, please give details below.  
 
I am a consultant for Natural Cycles - an app used for contraception.  
 
I agree to the open peer review policy of the journal. I understan d that my name will be included 
on my report to the authors and, if the manuscript is accepted f or publication, my named report 
including any attachments I upload will be posted on the website along with the authors ' 
responses. I agree for my report to be made available under an Open Access Creative Commons  
CC-BY license ( http://creativecommons.org/licenses/by/4.0/ ). I understand that any comments 
which I do not wish to be included in my named report can be included as confidential comments 
to the editor s, which will not be published.  
 
I agree to the open peer review policy of the journal