TABLE 3.

Variability of episiotomy rates between maternity units for each successive model and the percentage of variance it explains.

	Primiparous		Multiparous
	Variance	PCV (%)	Variance	PCV (%)
Model 0	0.422		0.335
Model 1	0.518	NC a	0.376	NC a
Model 2	0.481	7.2	0.317	15.5
Model 3	0.394	18.0	0.222	30.0

Note: PCV calculated in relation to Model n − 1: (${\tau }_{00}$ [Mn − 1] − ${\tau }_{00}\left[\mathit{Mn}\right])/{\tau }_{00}\left[\mathit{Mn}-1\right]$.

Model 0 = model empty.

Model 1 = M0+ individual characteristics (maternal, pregnancy, labor and delivery).

Model 2 = M1+ maternity unit characteristics.

Model 3 = M2+ French regions.

Abbreviation: PCV, proportional change of variance.

^a A negative PVE was a non‐contributory result and signified that the characteristics included in the model did not explain the variance in episiotomy use between maternity units.