I would think that you could probably find the transcripts, briefs and certainly opinions for Gonzales v. Carhart online. If it’s anywhere, that’s where it would be. But any argument would be, in my opinion, so far fetched as to be impossible.
They seemed to have claimed that since no one could say for "certain" what might threaten the mother's life, there being no medical "consensus" in this area, anything other than a narrowly defined prohibition to the procedure would constitute an "undue burden" and thereby violate a woman's "right" to chose to have an abortion and to not be unduly impeded in the exercise of said "right" by the Government.
The original desicion placed the onus on the legislature to narrowly define what would constitute a "threat to the mothers life" whereas this most recent desicion seems to have place the onus back on the abortion provider requiring them to define what condition would place the mothers life at risk and to justify the performance of the intact D&E (partial birth abortion) as the "sole remedy" to said condition.