What counts in any pack is fit to the individual, and, especially in BPJ's case, adjustibility. Is a significantly heavy backpack even a good idea in the third trimester? A a non-uterine members of the species, I honestly haven't a clue.

As an example of the adjustability issue, for Mark, "sternum straps are worth their weight in gold." For me, they are useless impediments and worthless (usually).

I would look to any number of civilian brands rather than the LE/military lines like Maxpedition, which are durable and tough, but nowhere as sophisticated as their domestic counterpart.