With my second dd, a successful, natural VBAC, I took oral EPO and drank RRLT during my last trimester... I've actually been meaning to look up when to start them both, as I'm getting up on six months with #3 now. I know I only took EPO for about a month, no more - maybe only about three weeks - and I am pretty sure I didn't start drinking RRLT until sometime in my late sixth month, possibly not til the seventh.
I was seen by a practice of six CNMs, all of whom were very supportive of my VBAC and all of whom knew about the EPO & RRLT and none ever mentioned that there might be potential problems from the tea... as it happened, I had a nice slow labor too (around 15 hrs), with nothing I would call really strong ctx til around transition - the last two and a half hours or so.
Also I do remember that my cervix was very ripe and soft during the last week or so, and as my c/s had been for FTP and I didn't begin labor until I consented to pitocin 10 hours after my water broke and only ever dilated to five cm, obviously I'll never know for sure but I felt like the EPO may have helped as far as ripening my cervix went.