In California can someone who does not disclose pregnancy during pre-employment interview be terminated after being hired?

Not for the fact of being pregnant. They can still be terminated for, for example, misconduct.

You are under no obligation whatsoever to discuss this or any other medical condition with your employer so long as you are able to perform the essential functions of the job (with reasonable accommodation, if necessary). Pregnant individuals are a protected class under anti-discrimination law. Just like with race or religion, you cannot be discriminated against on the basis of pregnancy.