attitudes towards pregnant employees

[allthegoodnamesweretaken]

Writing a short piece for uni on workplace discrimination, focusing on pregnant women. Got some useful statistics and things, but i was wondering if anyone knew if there have ever been any studies into the attitudes of employers towards pregnant employees? It would be useful to have stats to say so many employers felt that..insert unfair assumption here. But I am struggling to find anything.
Any help will be much appreciated :)