Oh yeah! Those were sequels of the TV episode , where Spock and McCoy are trapped in the Ice Age past of a doomed planet, along with the obligatory Beautiful Woman (who was exiled there as a political refugee). Those novels take up the question "What if Spock got The Beautiful Woman preggers while he was all id-ish with her?"

Entertaining, and worth reading.

(http://en.wikipedia.org/wiki/All_Our_Yesterdays_(Star_Trek:_The_Original_Series))