Published on in Vol 8, No 9 (2020): September
                                    Preprints (earlier versions) of this paper are
                                    available at
                                    https://preprints.jmir.org/preprint/19744, first published
                                    .
                                

1 Department of Obstetrics and Gynecology, Nara Medical University, Kashihara, Nara, Japan
2 NTT DoCoMo, Inc, Tokyo, Japan
3 TOITU Co, Ltd, Tokyo, Japan
