Missed Periods at 53: Pregnancy Risk & What to Do

Question
I am 53 years old and just recently missed 3 periods in a row, however this month I had a normal period.  I haven't been on birth control in a very long time.  Was always successful using the rhythm method.  My question now is whether I'm safe from getting pregnant since there is know way to determine the rhythm of my cycles?

Answer
Although pregnancy is unlikely, it's generally considered possible to get pregnant until you've gone for one year without a period.  I would recommend using something (foam?) for birth control until you've gone one year with no period.  As you say, rhythm doesn't work very well when you have no idea when your next period may be.  If you use nothing for birth control, most likely you'll never get pregnant at age 53, but there's a very slight chance.