It is a prospective cohort study.The primiparas in six geographic regions of China are recruited to observe the natural recovery of pelvic floor muscle. The pelvic floor muscle function is evaluated at 6 weeks,3 months and 12 months after delivery.

The primiparas in six geographic regions of China are recruited to observe the natural recovery of pelvic floor muscle.Evaluation of pelvic floor function is performed at 6 weeks, 3 months, 12 months after delivery. The modified Oxford Grading Scale and Levator ani testing are used to quantify PFM strength through vaginal palpation. Pelvic floor muscles strength, endurance, repetition,vaginal contraction pressure and the knack test are evaluated using a neuromuscular stimulation therapy system of PHENIX (Company: Vivaltis -Electronic Concept Lignon Innovation, Montpellier, France).

Inclusion Criteria:

1. Women who give birth for the first time （Including vaginal delivery and cesarean section）
2. Term birth（37-42 weeks）
3. Single birth
4. Aged from 18 to 50
5. Plan to live locally for extended periods of time

Exclusion Criteria:

1. A history of incontinence before pregnancy
2. A history of fecal incontinence before pregnancy
3. Pelvic organ prolapse before pregnancy （prolapse out of the hymen ）
4. A history of abortion or induced labour over 16 weeks of pregnancy
5. Multiple pregnancy
6. The weight of the newborn is less than 2500g or more than 4000g
7. Precipitate labour
8. Operative vaginal delivery（obstetric forceps or vacuum extraction）
9. Laceration of perineum at least level III
10. Request for pelvic floor rehabilitation exercise（patients who have entered the group can not train the pelvic floor muscle）
11. Obesity （BMI before pregnancy over 25, BMI=weight (kg) / height square (m2) ）
12. Asthma
13. Long-term abdominal pressure（chronic cough for more than 1 months ，long-term constipation ect.）
14. Diabetes
15. Cotugno's disease
16. A history of pelvic floor surgery in the previous years

Six geographic regions of China are needed to be covered, and more than 1-2 hospitals in each area should be included. The primipara are recruited while having their routine follow-up 6 weeks after delivery at the outpatient department in local hospitals.