The law does not require employers to include details of statutory entitlement to maternity leave and Statutory Maternity Pay (SMP) in the contract. Often, however, there will probably be a separate document, which you can study. Maternity regulations are complex and can be difficult to understand. There are several sources of information:
Most of these provide websites with lots of information, so if you have access to the web it would be worth searching these sites. If not, you can find information sources through your local phone book and the local library.