Our unit obtained grant from Health and Health Services_ Research Fund to conduct this prospective observational study. Using perineal ultrasound technology, the pelvic floor biometries of women who carry their first singleton pregnancy are demonstrated to have changes as the pregnancy progress. Symptoms of pelvic floor disorders, such as urinary incontinence, increase as the pregnancy progress. And some of the pelvic floor biometries are associated with the symptoms. Shortly after delivery, about 22% of women have levator ani muscle injury. There is increase in pelvic organ mobility and hiatal area after vaginal delivery. With a longer follow-up till one year, some recovery of the pelvic floor is observed. Some changes persist even in women received elective caesarean delivery without labour. By one year after delivery, when compared women delivered vaginally with women delivered by caesarean section, the only more commonly reported symptom is stress urinary incontinence. There is also a larger hiatal area on perineal ultrasound. Although levator ani muscle injury is a risk factor for a larger hiatal area, there is no significant difference in symptoms of pelvic floor disorders or quality of life between women with or without this condition.