Jamie Cost Beth Something Important
It is possible that when in their later teenage years, Beth was involved in a car accident that was caused by Jamie. Whatever the reasoning (tiredness, DUI, etc.), Jamie’s driving could have led to it, and my Yellowstone theory then speculates that after the wreck, Jamie (and John) might have thought that Beth was heading for a full recovery. However, Beth could have been told in confidence by someone on the medical staff that she suffered internal injuries and could no longer have children, which she could have theoretically kept a secret.