Board Thread:The Reference Desk/@comment-74.106.61.93-20130224211810/@comment-188432-20130303181533

We don't know. There is no direct narrative evidence to answer your question. A part of the reason we don't know is because it's unclear how much of a Time Lord River is. Without knowing that, it's impossible to even begin to speculate how many lives she may have passed on to Eleven.

The other part of the reason is that we don't know how serious any future production team will take the 13-life limit established in The Deadly Assassin. Given that the Fourteenth Doctor probably won't arrive much before 2020, it will have been 30 years since the last major onscreen mention of that limitation in the 1996 telemovie. By that point it's just as possible that the production team will simply not mention the 13-limit as they will explain how they got around it.

Certainly, Let's Kill Hitler provides an obvious reason why there could be a 13th regeneration and consequent 14th body — so obvious that all the newly-regenerated Fourteen has to say is "River" for the explanation to be complete.