"Spontaneous labor" refers to the natural and unplanned process of a pregnant woman's body going into labor and giving birth without any medical intervention or induced methods. Full definition
Contemporary patterns of spontaneous labor with normal neonatal outcomes. (acog.org)
In an ideal scenario, you would go into spontaneous labor before 41 weeks. (health.com)
This comparison is misleading because the actual clinical alternative to labor induction is not spontaneous labor (which may or may not occur) but expectant management. (journals.lww.com)