maternity pay entitlements

Hi guys! I've already tried to post a message but mustnt have worked. Basically me and my husband are really keen to start a family. However, we are wondering if the timing is right as I am currently employed as a staff nurse by the NHS on a 18 month temporary contract which is due to expire on 20th august 2013! Although my other half works I am the highest earner in our household so I would need to qualify for SMP to keep on top of our bills etc. If my calculations are correct I will need to have concieved before mid january in order to qualify...no pressure hehe! Have I calculated this correctly, I'm a little confused at present x