I would certainly check with your HR department to be sure, but my understanding is that, in situations like yours, the bed-rest period before the birth would not count as maternity leave because it was not taken "for the purpose of giving birth."  (See Massachusetts General Laws chapter 149, Section105D.)  Also, this section from 804 CMR 8.01 (Massachusetts regulations) seems to speak  to your issue as well:
 
3) Pregnancy-Related Disabilities. Disabilities caused or contributed to by pregnancy, miscarriage, abortion, childbirth, and recovery therefrom are, for all job-related purposes, temporary disabilities and should be treated as such under any health or temporary disability insurance or sick leave plan available in connection with employment. Written and unwritten employment policies and practices involving matters such as the commencement and duration of leave, the availability of extensions, the accrual of seniority and other benefits and privileges, reinstatement, and payment under any health or temporary disability insurance or sick leave plan, formal or informal, shall be applied to disability due to pregnancy or childbirth on the same terms and conditions as they are applied to other temporary disabilities; provided, however, that if a disability caused or contributed to by childbirth and recovery therefrom is less than eight weeks duration or if a temporary leave policy of an employer would result in a maternity leave of less than eight weeks, a female employee who meets the requirements specified in M.G.L. c. 149, s. 105D shall be entitled to an eight week maternity leave. Nothing in the above subsection of this regulation shall be construed to limit provisions of M.G.L. c. 149, s. 105D.
 
So, you may be able to take sick leave or be entitled to leave under your employer's disability policy.  You should also check to see if you qualify under the federal maternity leave act.  Good luck.