Thor's Hammer was fixed in Thor's Chariot, wasn't it? Was there some reason why Sha're could not have been taken back to Cimmeria during that brief window of opportunity?
The hammer damn near killed Teal'c. To death.
Imagine for a moment what it would do to a pregnant woman.
There are a few other concerns as well:
The Asgard improved the AI on the hammer: Teal'c is explicitly mentioned, but it makes sense that the change that was actually done was to allow all friends of the Tau'ri, likely making the hammer unable to detect Sha're as a threat.
The hammer might not be able to detect the presence of a dormant Goa'uld in any case.
The SGC might have compunctions about sending a highly pregnant woman through the Stargate, especially if it is to potentially die at the hands of an Unas in a dark and horrible dungeon, or to potentially be killed by an Asgard device.
While the hammer might indeed correctly recognize Sha're as a threat, tackling her like O'Neill did to Teal'c the first time around certainly wouldn't work, leading either to her not being taken to the dungeon at all, or her being sent and Daniel being ignored, leaving her alone and likely in shock-induced labor, a moderately suboptimal situation.
Given the above concerns, the risk/reward calculations are looking pretty bleak. Kind of.
A darker analysis reveals, of course, that Sha're losing the child might not have been a terrible thing, all things considered, and would likely ingratiate the SGC with the System Lord collective, but bring down upon them the full force of Apophis, who at the time was otherwise occupied.
Of course, late third trimester abortions aren't only morally difficult, they are also a dangerous proposition for the mother, further impacting the risk/reward calculus.
Additionally, they might simply have failed to consider it. SGC staff is notoriously forgetful when it comes to this kind of stuff.
And, finally, on the meta-level,
saving Sha're was never an option.
It would completely derail Daniel as a credible team member, destroying his motivation.
Instead, her later death steels his resolve to exterminate the Goa'uld and everything they represent; further cementing his path towards the dark side; making his later realization of what he is becoming and subsequent redemption all the more powerful.
The thing is, one way or another, they should have brought her to Earth to have the child (a human, innocent child) and, as they had talked about in that very episode, use her for intelligence purposes (Daniel and her already agreed on that).
That would have her available to ANY method of extracting the Goa'uld (after giving birth is you're so worried about her pregnancy), like the Asgard (they created the Hammer, so...) and, a few episodes later, Marchello's larvae or whatever they were, especially created to free the host -safely- killing the bug.
In the real world, however, I suspect they wanted to free Daniel for future flirting.