Make sure you take your prenatal vitamins and have all the prenatal screenings done, even the non mandatory ones. Also make sure that you take it very easy as pregnancy is hard on the average 25 year olds body so it will be even harder on a woman who is of advanced maternal age such as 45.
You should know that you are at high risk for you and your baby to have problems. It is very important to get to the doctor as soon as possible and to take good care of yourself, including eating healthy, getting plenty of rest, exercise, and enjoying the pregnancy with your spouse.
Birth defects rapidly increase with age. Talk to your doctor, what tests are needed, will some of those tests make a difference to you? Would an abortion ever be an option for you? If no, then some tests that are recommended for advanced maternal age may not be for you.
Follow up with your OB/GYN and make sure to take your prenatal vitamins. Get a lot of exercise and eat properly. Your pregnancy may be high risk given your age, but nothing to worry because women your age are having babies all the time today's society. Follow traditional baby books! Congrats!
Rarely women become pregnant after 45. At this age your muscles becomes hard and must go for checking frequently. You should do minor exercises so that your muscles become loose. Exercise should be done in consultation with your gynaecologist. Consult the same gynaecologist from now on till birth of baby.