You might, depending on the facts of your specific situation. California law protects employees who take maternity leave, and it sounds like your employer may have violated California law by terminating your employment while you were on maternity leave.
However, there are many factors that will determine whether you actually have a case. You should consult with an experienced California employment law attorney. My firm provides free consultations; feel free to call us at 213-201-9331.
Your question provides very little information. If the employer's decision to lay you off was motivated by your pregnancy, then you may have a claim for pregnancy discrimination.
I do not understand the issue relating to health insurance. Generally, employers are not required to provide health insurance. Are you saying the employer denied you health insurance, because you were pregnant? If so, that would be illegal and you may a claim for pregnancy discrimination for reason too.
It is unlawful to terminate you for being pregnant or for taking maternity leave. It is not unlawful to terminate you during pregnancy or pregnancy leave for an unrelated reason. If you were truly "laid off" rather than terminated, meaning you were discharged for lack of work based on seniority or another contractual basis and subject to recall if the demand for labor is restored to former level, then it is unlikely that the lay-off is actionable discrimination.
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The attorneys who have answered your question are correct. If your employment was terminated BECAUSE of your pregnancy or because you took eligible or protected leave, you may have a case for wrongful termination/discrimination, etc. More facts are needed to assess your matter. Call an employment law attorney to discuss. 949-481-6909.