Does the emission of a small amount of madhy (pre-seminal fluid) – less than a drop – from the outer vulva invalidate wudu (ablution)?

The solution is to avoid obsessive doubts (waswasah). If what occurred was merely obsessive doubt, then disregard it, and your ablution (wudu') is valid. However, if you are certain that pre-seminal fluid (madhi) was discharged, then it nullifies ablution, whether it is a small or large amount. Yet, it only nullifies ablution if it emerges to the outer part of the private organ (dhahir al-farj), which is what becomes visible when a woman squats to relieve herself. If the pre-seminal fluid does not reach the outer part of the private organ, it is not considered to have exited, and thus it does not nullify ablution.