Discrimination against an employee because of her pregnancy is unlawful. However, if your employer would have laid you off anyway, as you mention they did many others, it is not unlawful. FMLA only guarantees return to your job or an equivalent position IF the company would have not let you go for lawful reasons. Whether there is a notice of lay off requirement depends on the number of employees your employer has. It is called the WARN act but only applies to employers with a certain number of employees.