What does Genesis 25:22 mean?

Rebekah, formerly unable to have children, becomes pregnant after Isaac prays to the Lord for her. In fact, she is carrying the double blessing of twins. Rebekah likely doesn't know she is carrying twins, and her pregnancy doesn't appear to have felt especially "blessed" to her. Carrying two children at once is hard enough, but these unborn rivals seem particularly active. As this verse notes, the twins are "struggling" against each other, a comment which makes more sense once we've seen all that will occur between them in the future. The kicking and writhing of the children in her womb grows to the extent that it worries Rebekah.

Keep in mind that Rebekah does not have the medical technology available in the modern era. She probably has no idea that she's bearing twins. All she knows is that something is wrong. The struggle within her gets so bad for Rebekah that she finally wonders "why is this happening to me?" or perhaps "why am I here?" Overcome, she goes to inquire of the Lord. We're not told what form her prayer may have taken. It's possible she went to a sacred place or consulted a prophet, but she does receive a very specific response from the Lord in the following verse.