Re: but ew, cooties!
Thanks, but I've been married, and without going into unnecessary detail, there's one particular fluid that is most likely to be exchanged and retained by the female member of a male-female partnership, and it ain't saliva.
Which is all really beside the point, as this premise sort of depends on some of the smartest people in the Marvel Universe being either massively stupid or unable to deal with basic birds and bees conversations on any level. The Fantastic Four, the Hulk, Spider-Man, and Daredevil all got their powers after being exposed to radiation, and of those, Sue Richards miscarried her second pregnancy (after Franklin, before Valeria) and Betty Ross died (although that may been as a result of her being deliberately poisoned by Abomination?). Also, Peter himself has had numerous side-effects as a result of his mutation and other factors, including (at one point) sprouting two additional pairs of arms.
So, in all that time, Reed Richards, Bruce Banner, Henry Pym, Henry McCoy, Curt Connors, and other assorted scientist types, never, not once, thought to run a Geiger counter, that cutting-edge technology of 1908, over Peter (and everyone else who has either gotten their powers by radiation, been exposed to a radiation source, or fought with the likes of the Radioactive Man, which is to say, just about everyone who has ever put on a spandex costume)? Or, in the case of Richards et al., just having them built into their labs as a matter of course? Really?
There's suspension of disbelief, and then there's saying that, well, I haven't actually seen anyone running a Geiger counter over Peter, so hey, plot device. Not buying it for a second.