But they had no child, because Elizabeth was barren, and they were both well advanced in years. Luke 1:7
We do not know from the scriptures how they knew it was Elizabeth, but between Zacharias and his wife they could not produce a child. The story would not be quite the same if God had selected from among the Israelites a couple who had already produced a dozen children but hadn't had any for a few years. A late surprise blessing has happened to many a couple through the ages. It is like God wants to set the stage for His works with a bit more difficulty than the norm. This of course we know from many stories in the Bible. Daniel wasn't lowered into a den of kittens; that wouldn't be much of a story. Some of us might even consider that a bit of Heaven. Instead we read a grand story of famished lions, a concerned ruler, and an angel. Wonders indeed!
So, if your circumstances seem a bit strained, perhaps God is preparing your story for His grand entrance and a mighty work.
Marvel and wonder fill your works, O Lord!
Bucky