The day she defeated Arymilla, Elayne was roughly at the 60th day or her pregnancy, which means she's something like 30 weeks (ours) from giving birth yet.

Don't expect her to give birth in TOM.... especially not to healty babies!

She's set to give birth only toward the end of AMOL, most likely, and for her to give birth before the epilogue section, it would mean the last book will suddenly increase pace massively (ie: events won't be described in nearly as much details or there will be many gaps in the timeline during the LB - that we won't see every little battle but go from important events to important events set weeks later). It's possible, because already in TGS we started skipping weeks (eg: at the beginning of Rand's storyline, and there was a gap of well over a month in the middle of Egwene's storyline as well).