Fasting is not invalidated; because the woman's vagina is not one of the legally recognized openings through which fasting is invalidated by the entry and settling of something within it. The same ruling applies to anything that involves inserting a body into the woman's vagina, such as: the process of injecting sperm, or extracting eggs, or returning them, or inserting an IUD, or performing a hysteroscopy, or using vaginal suppositories during the day of Ramadan.