Results from segmented regression analysis for six clinical performance indicators and two internal validation outcomes from Ontario birth registry data sets, and four clinical performance indicators from an external data set (British Columbia), 2009–2015
| Parameter estimate (%) and 95% CI | P value | |
| Primary analyses | ||
| Indicator 1—unsatisfactory newborn screening samples | ||
| Intercept (baseline rate) | 2.25 (1.27 to 3.23) | 0.004 |
| Preintervention slope (per quarter) | 0.00 (−0.13 to 0.14) | 0.97 |
| Change in level after intervention | −0.68 (−2.29 to 1.22) | 0.49 |
| Change in slope (per quarter) after intervention | 0.10 (−0.18 to 0.38) | 0.50 |
| Postintervention slope (preintervention slope plus change in slope) | 0.10 (−0.40 to 0.60) | 0.71 |
| Indicator 2—episiotomy | ||
| Intercept (baseline rate) | 12.68 (12.36 to 13.00) | <0.001 |
| Preintervention slope (per month) | −0.03 (−0.05 to −0.02) | <0.001 |
| Change in level after intervention | −0.85 (−1.51 to −0.19) | 0.01 |
| Change in slope (per month) after intervention | −0.02 (−0.06 to 0.01) | 0.20 |
| Postintervention slope (preintervention slope plus change in slope) | −0.05 (−0.09 to −0.02) | <0.001 |
| Indicator 3—formula supplementation | ||
| Intercept (baseline rate) | 33.48 (33.15 to 33.82) | <0.001 |
| Preintervention slope (per month) | −0.08 (−0.09 to −0.06) | <0.001 |
| Change in level after intervention | 2.02 (1.29 to 2.74) | <0.001 |
| Change in slope (per month) after intervention | −0.07 (−0.11 to −0.02) | 0.004 |
| Postintervention slope (preintervention slope plus change in slope) | −0.14 (−0.18 to −0.10) | <0.001 |
| Indicator 4—elective repeat caesarean delivery prior to 39 weeks | ||
| Intercept (baseline rate) | 58.31 (57.92 to 58.70) | <0.001 |
| Preintervention slope (per month) | −0.21 (−0.23 to −0.19) | <0.001 |
| Change in level after intervention | −5.30 (−6.17 to −4.43) | <0.001 |
| Change in slope (per month) after intervention | −0.17 (−0.22 to −0.12) | <0.001 |
| Postintervention slope (preintervention slope plus change in slope) | −0.38 (−0.46 to −0.34) | <0.001 |
| Indicator 5—GBS screening | ||
| Intercept (baseline rate) | 92.91 (92.66 to 93.15) | <0.001 |
| Preintervention slope (per month) | 0.02 (0.00 to 0.03) | 0.007 |
| Change in level after intervention | −0.40 (−0.91 to 0.12) | 0.13 |
| Change in slope (per month) after intervention | 0.11 (0.08 to 0.14) | <0.001 |
| Postintervention slope (preintervention slope plus change in slope) | 0.12 (0.10 to 0.15) | <0.001 |
| Indicator 6—postdates induction prior to 41 weeks | ||
| Intercept (baseline rate) | 21.55 (19.90 to 23.20) | <0.001 |
| Preintervention slope (per month) | 0.09 (0.01 to 0.17) | 0.02 |
| Change in level after intervention | 0.36 (−3.69 to 4.41) | 0.85 |
| Change in slope (per month) after intervention | −0.40 (−0.59 to −0.21) | <0.001 |
| Postintervention slope (preintervention slope plus change in slope) | −0.31 (−0.50 to −0.12) | 0.002 |
| Control analyses | ||
| Internal control outcome 1—caesarean in induced nulliparous women | ||
| Intercept (baseline rate) | 30.08 (29.46 to 30.70) | <0.001 |
| Preintervention slope (per month) | 0.04 (0.01 to 0.07) | 0.01 |
| Change in level after intervention | −0.90 (−2.11 to 0.31) | 0.15 |
| Change in slope (per month) after intervention | 0.02 (−0.04 to 0.09) | 0.47 |
| Postintervention slope (preintervention slope plus change in slope) | 0.07 (0.01 to 0.12) | 0.03 |
| Internal control outcome 2—use of auscultation | ||
| Intercept (baseline rate) | 39.50 (37.39 to 41.60) | <0.001 |
| Preintervention slope (per month) | 0.23 (0.13 to 0.34) | <0.001 |
| Change in level after intervention | 5.91 (0.48 to 11.34) | 0.01 |
| Change in slope (per month) after intervention | −0.29 (−0.05 to −0.04) | 0.01 |
| Postintervention slope (preintervention slope plus change in slope) | −0.06 (−0.31 to 0.19) | 0.65 |
| External control indicators (British Columbia data set) | ||
| Indicator 2—episiotomy | ||
| Intercept (baseline rate) | 6.12 (5.92 to 6.32) | <0.001 |
| Preintervention slope (per month) | −0.03 (−0.04 to −0.01) | <0.001 |
| Change in level after intervention | 0.09 (−0.37 to 0.56) | 0.67 |
| Change in slope (per month) after intervention | 0.02 (0.00 to 0.05) | 0.08 |
| Postintervention slope (preintervention slope plus change in slope) | −0.01 (−0.03 to 0.02) | 0.69 |
| Indicator 4—elective repeat caesarean delivery prior to 39 weeks | ||
| Intercept (baseline rate) | 50.17 (47.18 to 53.17) | <0.001 |
| Preintervention slope (per month) | −0.18 (−0.35 to −0.02) | 0.01 |
| Change in level after intervention | 4.60 (−1.37 to 10.57) | 0.11 |
| Change in slope (per month) after intervention | −0.23 (−0.06 to 0.10) | 0.13 |
| Postintervention slope (preintervention slope plus change in slope) | −0.41 (−0.69 to −0.13) | 0.004 |
| Indicator 5—GBS screening | ||
| Intercept (baseline rate) | 92.84 (92.57 to 93.11) | <0.001 |
| Preintervention slope (per month) | 0.00 (−0.01 to 0.02) | 0.49 |
| Change in level after intervention | 0.90 (0.33 to 1.47) | 0.002 |
| Change in slope (per month) after intervention | −0.02 (−0.05 to 0.01) | 0.17 |
| Postintervention slope (preintervention slope plus change in slope) | −0.02 (−0.05 to 0.02) | 0.25 |
| Indicator 6—postdates induction prior to 41 weeks | ||
| Intercept (baseline rate) | 16.33 (16.08 to 16.59) | <0.001 |
| Preintervention slope (per month) | −0.07 (−0.08 to −0.06) | <0.001 |
| Change in level after intervention | 0.47 (−0.19 to 1.22) | 0.15 |
| Change in slope (per month) after intervention | 0.09 (0.06 to 0.13) | <0.001 |
| Postintervention slope (preintervention slope plus change in slope) | 0.02 (−0.01 to 0.05) | 0.21 |
GBS, group B streptococcus.