In asymptotically flat spacetimes, the area of a black hole event horizon must always increase, provided the Null Convergence Condition is followed ($R_{\mu\nu}k^{\mu}k^{\nu}\geq0$ for all null vectors $k^{\mu}$) (S.W. Hawking, Gravitational radiation from colliding black holes, Phys. Rev. Lett. 26 (1971) 1344.). This is sometimes called the "second law of black hole thermodynamics".
Does this result also hold for black holes in asymptotically FLRW spacetimes (expanding and/or contracting)? I am mostly trying to find papers on this subject; I have only found this paper by Hawking and Gibbons on black holes in asymptotically de Sitter spacetimes.