Complex sentence: It takes little vaginal secretion to make the vagina moist; in this case, the secretions may be little excess during sexual arousal, the middle of the menstrual cycle, a little prior to menstruation, or during pregnancy.
Split into simpler sentences: It takes little vaginal secretion to make the vagina moist. The secretions may be minor in excess during sexual arousal, the middle of the menstrual cycle, a little prior to menstruation, or during pregnancy.