Congratulations for putting your baby's safety and yours first!
In my opinion, it is perfectly reasonable to request a leave under these circumstances. Another option might be to request a transfer to a non-patient care position, but that is probably not likely to happen.
I suggest that you request a meeting with your HR representative so that you fully understand the FMLA policy of your employer.
Generally speaking, if your physician documents a need for leave, your employer must comply, but there are limits to the benefits you will receive. Most employers allow 12-13 weeks total FMLA time per year. At 26 weeks gestation, you may use that entire amount before your baby is due. If so, will you be able to get an extension? If your employer says yes, please get that in writing, along with the terms of the extension (Insurance coverage? Same position and shift held for you?) Also, during your leave, you must continue to pay the employee portion of your benefits. Do you have the funds to do so if you are not bringing in any income? Lastly, do you intend to return to work at the conclusion of your leave? If you do not return in a benefits-eligible position, your employer has the right to bill you for the cost of the benefits provided during your leave. (Not all do, but it is their legal right.) So if you don't intend to return, it might be best to find out if you are covered under your spouse's insurance before taking your leave.
I'm not trying to discourage you from taking a leave, just want to make sure that you don't end up with any unpleasant expenses afterward.
Take good care of yourself and your wee one!