Funding for this research was provided by:
Medical Research Council
Received: 6 June 2018
Accepted: 3 October 2018
First Online: 11 October 2018
Ethics approval and consent to participate
: This research had the approval of Newcastle University’s Ethics Committee in 1978. Date of approval (given to Prof. Tom Lind) and reference number are not currently available. All the women gave written informed consent to participate.
: All the women gave written informed consent to publication of de-identified data.
: The authors declare that they have no competing interests.
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