While FMLA can be used in the case of a pregnancy you have to meet the following conditions first:

In order to be eligible to take leave under the FMLA, an employee must (1) work for a covered employer, (2) work 1,250 hours during the 12 months prior to the start of leave, (3) work at a location where 50 or more employees work at that location or within 75 miles of it, and (4) have worked for the employer for 12 months.

So basically if you work for a smaller company, or just started, you can’t use it.

Also note the per location employee rule. You could have a large nationwide business that purposely keeps the regional employment low in order to circumvent FMLA payouts