Factors associated with spontaneous vaginal birth in nulliparous women: A descriptive systematic review.

Problem: Spontaneous vaginal birth (SVB) rates for nulliparous women are declining internationally.

Background: There is inadequate understanding of factors affecting this trend overall and limited large-scale responses to improve women's opportunity to birth spontaneously.

Aim: To undertake a descriptive systematic review identifying factors associated with spontaneous vaginal birth at term, in nulliparous women with a singleton pregnancy.