best way to create a curved edge??

i have been working with the cloth sewing patch for the last couple days and i now need help in doing the modeling for the pattern parts.

starting with a grid what is the best way to make a curved edge that
1 can be controlled easily
2 will not add unneeded verts

as an example on a 16 by 16 grid i want to have a curve going from 16,9 to 12,16 curving “upward” (this will be part of the leg opening for a leotard btw)