I forget the details...its been 13 years...but that was one of the more open-and-shut points our attorney used to easily force a settlement.
You do know there are federal employment laws that make it illegal to fire women just for being pregnant, don't you?
Also, there was no documented reason why they were firing her...her work record was spotless and in fact, she was the new store trainer for her position due to her hard work and skill.
One of the more egregious things I remember was the manager actually called her and told her, while she was in the hospital no less, that they would rehire her after my daughter was born, even thought they just cancelled her insurance and left us both in a huge financial bind and put her health and her baby's health is serious risk.
Do you really think that women should be fired and have their health insurance cancelled for no reason besides being pregnant?
If so, that is truly disgusting.
The other way is to look for patterns over a longer period of time and maybe say "look all 10 last employees who were let go were women who got pregnant, there is something here".
But unfortunately if they are not too stupid they would use convenient double-speak euphemisms between themselves. Like say they'd call it "restructuring". Or due to "culture fit". Or just "business reasons". They could be winking to each other when saying that but you'd really need of the people in charge to turn on others and testify.