I assume the Biorg don't assimilate babies. What's the right age for somebody to be assimilated? What about pregnant people? Do they assimilate them too? What happens to the baby? Do the borg have sex with eachother?
There was also the magic Borg baby from the VOY episode that introduce Icheb and the other kids...you know the baby that was in trouble and beamed back to Voyager then recovered, only to vanish from continuity altogether The Borg use maturation chambers to speed up the growth of children the assimilate (Seven, Icheb, etc), so babies would be included in that as well. As for pregnancies, I would see them being terminated during the assimilation process thanks to the nanoprobes.
The infant drone in "Collective" would seem to imply that the Borg do sometimes assimilate infants. The relevant question is, can most infants survive the assimilation process, and do the Borg therefore make infantile assimilation a standard practice? We don't know. I imagine they would. I would be willing to bet that the fetus would die as a result of assimilation, however. No. It's canonically established that the Borg do not reproduce this way; they reproduce by assimilation. However, for whatever it's worth, the novel Great Than the Sum by Christopher L. Bennett establishes that the Borg also reproduce by growing genetically-engineered humanoids who are neuter; these neuter drones are identified as the type seen in TNG. Assimilated humanoids are identified as the type first seen in First Contact and then seen throughout VOY. Bennett posits that we saw so many assimilated FC-style drones in VOY because so many billions of neuter drones had died in the war with Species 8472, prompting the Collective to quickly replenish its drone stock by assimilating many more innocent victims.