This study is a cohort clinical study. Baseline data were collected from cases recruited at pregnancy, and the eligible subjects were grouped into 3 groups according to different delivery position including supine position group, upright position group, and lateral position group. Different delivery positions along with respectively timeand obstetric conditions were recorded at delivery. Pelvic floor function assessments were performed at postpartum.

Inclusion Criteria:

1. Age 20-35 years old
2. Singleton, cephalic position, full-term primipara;
3. Cephalopelvic disproportion;
4. Expected fetal weight< 4000g;
5. Intended vaginal delivery in our hospital;
6. Voluntary participation of study subjects.

Exclusion Criteria:

1. Pelvic floor organ prolapse beyond the hymen limbus;
2. Combined with uncontrolled medical diseases and asthma, allergic rhinitis and constipation before pregnancy;
3. Presence of contraindications to vaginal delivery

Singleton, cephalic position, full-term primipara aged 20-35 years old without cephalopelvic disproportion, expected fetal weight ≥ 4000gpelvic floor organ prolapse beyond the hymen limbus and combined with uncontrolled medical diseases and asthma, allergic rhinitis and constipation before pregnancy.

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