Okay, I went and checked the original guide, and grabbed the table for length of pregnancy from there. All we need is an entry for Half-Orcs, and we are all set there. I'd like to add the average difficulty ratings for pregnancy/birth to that table as well, so I'll be thinking about that and see if I can come up with anything.
Afterthought: The current table for length of pregnancy has fixed lengths. What do you guys think about changing that to something akin to the height/weight tables in the PHB? So, for Humans, instead of stating 9mo, we could do a 7 + 1d3 months. Elves normal length of pregnancy is 24, so there could be even more variation. Half-Breeds would have the biggest variation, since it would be a mix between the two parent races. So, for a half-elf, it could be anywhere from 9 to 24 months. I kinda like a little bit of randomness, especially for something like pregnancy.
Also, as far as ovulation goes, upon re-reading the segment on conception yet another time, it finally dawned on me that ovulation is already covered in the base fertility DC, so we don't really need yet another piece of information in there. The poor half-orc women have a really short menstrual interval... I really feel sorry for their males...
Also, just as a general FYI: I obtained some more artwork, which I'll upload over the next few days. We are doing pretty well on the Prestige Classes, and I also received some (non-elven) artwork that will look great in the race chapter.