In the third season of Big Love (not the most recent one), Seyfried's character has premarital sex and gets pregnant, much to the shock and offense of her polygamist parents. The "problem" (if I recall correctly, abortion isn't even mentioned, which seems fairly realistic in context) is solved when she miscarries, although the issue was returned to in the most recent season when Sarah married her boyfriend and then transferred her affections to another woman's baby.
Seyfried told the NY Daily News, "I just really wanted to be pregnant and that fit with the third season and then I had a miscarriage. Damn it!" She also said, with a "grimace," apparently, "The evolution of Sarah has pretty much run its course."
It's not really clear from her comments whether she objected to the miscarriage because it's a fallback for television writers who start something they don't know how to finish (or are afraid of the issues it raises) or because she was robbed of the experience of playing a pregnant and then young mother character. If she returns to the show, Seyfried said, she'll be a supporting character:
"I'll come back from Portland, probably, hopefully, be pregnant. We'll see. She's just grown to a point where I don't know what else they can do with her."
Seyfried or no, next season better not give us the impression that the writers have no idea what else they can do with the characters. What a waste of a promising, female-driven show. And perhaps there's a correlation between a show with strong roles for women and actresses who freely complain when they don't live up to their potential.
Related: Convenient Miscarriage [TV Tropes]