Gender is an essential characteristic - Russell M. Nelson

We also know that “gender is an essential characteristic of individual premortal, mortal, and eternal identity and purpose.”

Russell M. Nelson, Decisions for Eternity, 2013 Semiannual General Conference for The Church of Jesus Christ of Latter-day Saints

https://www.churchofjesuschrist.org/study/general-conference/2013/10/decisions-for-eternity?id=p23&lang=eng#p23