Why do we wanna see a pregnant lois lane??? Same goes to a pregnant snow white or a pregnant cinderella. It hasn't done before, mostly because it's a bad idea.
There have been a huge number of pregnant storylines across various media. Pregnant Snow White has actually been done by the way, in the decently rated and (imo) well-written show
Once Upon a Time, and actually many of the best Snow White scenes are those of Snow White as a mother. Further, the show
Lois and Clark was going to go with Lois and Clark as parents in their fifth season, but they got canceled. We see the baby show up in the season 4 finale. I for one am curious where they would have gone with it.
Magic pregnancy storylines are a big deal:
http://io9.com/the-most-ridiculous-mystical-pregnancies-in-fiction-1444515141
Even MoS has a magic pregnancy storyline, an inverted one so to speak, as Kal-El is the first Kryptonian child in a 1000 years to originate from a good **** rather than from a test tube. One of the foundational documents of our culture, the New Testament, is all about a magic pregnancy, a virgin birth.
Though I'm not saying that a magical pregnancy is necessary to a Lois Lane pregnancy storyline. They could even have a normal kid.
I'm not even saying I necessarily want to see a pregnant Lois Lane storyline, but I'm saying it's possible I could enjoy it, I'm not sure, it's not obvious. I think it's a legitimate option and I hope that Goyer and Snyder at least consider it.
It can add a different side to the characters that we have not seen on screen before. Given that Goyer has gone for a completely different take on the Clois relationship, one where they rapidly become a couple (in most interpretations it takes some time), they might as well consider taking advantage, and showing us the later relationship stages.
As an example, in
Lois and Clark season 4, there were several fun plot points involving pregnancy. First of all, they had to deal with the uncertainty that they did not know if they could even have a kid. We saw Lois cry when she learned she could not have a kid, and Clark held her and said to her "I'm sorry, I always swore I would never make you cry" [paraphrased]. Second, Lois was having nightmares about having superbabies and having no idea how to deal with them. This adds a lot of humanity to the characters, and it's a fun thought-experiment. As another example, the excellent animated movie
All-Star Superman ends with a redeemed Lex Luthor giving Superman a potion that will allow him to have children with Lois, which is actually my favourite ending of any Superman movie.