Yukkuris get pregnant when they eat or touch seminal liquids, i.e. Yukkuri-in-heat's filling or human semen. In the case of human semen, the result is a Half-Yukkuri, which starts its life with a short and pudgy body and ten years later, if they can live that long, it develops a well formed feminine body, smaller eyes and doesn't develop a nose.
In the case of this picture, it is impossible that the Yukkuri will get pregnant, vaginal fluid is just a lubricant. In the improbable case that a Yukkuri could get pregnant when exposed to vaginal fluids, it is necessary that the fluids come from a different Touhou Project: Yukkuris reproduce when they mate with Yukkuris of different type, except for Yukkuri Rinnosuke.