Don't believe that such information is available. You can, and probably have, accessed all authoritative resources available. To the best of my knowledge there have been no formal studies of Kaletra or Combivir during pregnancy in humans and the animal studies are indeed conflicting.
The most recent information on the combination of these drugs (Mar 15, 2012) and available on-line can be found here >Combivir and Kaletra drug interactions, a post-marketing study by eHealthMe.com
. Unfortunately this site lends nothing to the question of pregnancy and is un-referenced.
Wish I could be of more help.