Wow, it's been ages since I posted here, but as I'm a doctor and TV channel recently rebroadcast all the Sg-1 episodes which got me thinking again about the subject of Goa'uld reproduction. I've come up with a theory that should hopefully settle the debate we had several years ago.
We know that in their natural environment Queens grow a sac in order to give birth to their young. In a human host a sac of that size would never fit, so how would a Queen give birth? I believe that the Queen does extend herself down the spine to the host's reproductive system, but only in a very limited way, a set of thin filaments and no more. These grow down to the ovaries, piercing them and expanding out to encompass the space, ejecting the human eggs. The Queen them grows the necessary equipment for egg production within the ovary and when the time comes to give birth the eggs set off towards the uterus at regular intervals.
Next comes the part about ensuring compatibility between species. I would guess that the goa'uld somehow fools the human sperm into thinking that the egg is human and needs to be fertilised, and it bonds with the (soft shelled?) egg, and the human dna is spliced to the larvae's own. I'd guess that maybe another 'filament' is extruded by the symbiote down to the uterus to aid with collection, storage and use of the code of life.
Following the splicing, the egg then proceeds into the uterus proper, where it hatches. The Queen has already stimulated the production of a large quantity of rich amniotic fluid which helps the larva to develop rapidly. I'd also venture a guess that the eggs are laid in time delayed over several hours, which prevents any damage to the host's organs from having too many baby snakes wriggling around.
From the time spans involved with Hathor, we can confidently say that the larvae do indeed develop extremely rapidly and probably spend time developing outside their mother's host body. So, probably within half an hour of hatching the larva is expelled from the host body, probably with a quantity quantity of amniotic fluid that helps with development. For starters we know that there was definitely something in the water, as firing bullets at water doesn't usually cause it to catch fire, but also it makes sense from a developmental perspective.
Now that I've said all that I don't intend to think about it ever again. I know nobody is likely to read this anyway, but I needed to get it off my chest somewhere, and Maureen btw I miss your amazing fanfics