Which policy do I adhere by if I told my employer I was pregnant and then a month later the leave policy changed?

Notwithstanding your employer's personnel policies, California law provides for pregnancy leave under the California Fair Employment and Housing Act:

California employers with five or more employees are subject to FEHA's pregnancy disability leave (PDL) law, which gives employees who are disabled because of pregnancy up to 4 months of unpaid leave. Govt C §§12926(d), 12945(a)(1). The employer must maintain group health insurance coverage for employees during a PDL leave on the same terms as if the employee had continued to work. If the employee fails to return to work after the leave expires, the employer may be able to recover premiums paid during the leave. Govt C 12945(a)(2)(A).