I had post-sex urine leakage what could it be?

Bladder irritability: If you are a woman.........With advancing age and decreasing vaginal estogen, the bladder becomes less tolerant of stimulation. Whether it is tomatoes, carbonated drinks, caffeine, or intercourse, the stimulation is not tolerated by the bladder muscle as well so the bladder muscle responds by contracting. Infections can cause this also. Medications and good kegel exercises can help with this.