Since I'm up way too early....

from the script:

Quote
LUCY
I'm not just talking about the
ball, Lois. You have to get out *
more.

LOIS
Will you stop? You sound like Dad.
Jeez, I'm only twenty-six.
And Clark was a year older.

So that makes Lois 16 when she gave birth and maybe 15 when she got pregnant, although she could have just turned 16.

Given that age, it's not likely she and Clark would have married BP (before pregnancy) but rather after she found out. Just the way RL goes.

c.