Either the employer, the employee, or a split between the two.
This is why "fairness" is for kids in the schoolyard and referees in artificial situations, and not for adults. Every time someone is treated "fairly" because of government intervention, someone else gets hosed. But they're invisible, so nobody cares.
Pregnancy isn't a disability. It's the result of a purely voluntary activity. [If you want to allow a disability exemption for cases where rape charges are filed, I'm not going to quibble about that.]