Table 3.

Multivariate Analysis Using a Binomial Logistic Regression Model of Matched Cases and Controls

Variable	Odds Ratio (95% CI)
Rotation (not required)	Ref
Rotation (required)	2.24(0.97 – 5.26)
Birth weight (per 100g increase)	1.14 (1.08 – 1.22)*
Time fully dilated	1.01 (1.00 – 1.01)*
Parity	0.87 (0.58 – 1.27)
Maternal age	1.02 (0.97 – 1.07)
Day shift	Ref
Night shift	1.24 (0.75– 2.06)
Instrument (forceps)	Ref
Instrument (ventouse)	0.90 (0.54 – 1.50)
Ethnicity - Caucasian	Ref
Ethnicity - Black	0.73 (0.03 – 6.35)
Ethnicity – Southeast Asian	1.99 (0.69 – 5.57)
Ethnicity – other/unknown	5.29 (1.27 – 24.59)
No epidural	Ref
Epidural	1.20 (0.70 – 2.06)

All cases of unsuccessful instrumental delivery are matched to cases of successful instrumental delivery within the same shift, where such a case exists. Where an unsuccessful instrumental delivery has no successful delivery within the same shift, it is not included in the analysis. Where multiple successful deliveries occur within the same shift as an unsuccessful delivery, all matches are included in the analysis. Model coefficients are expressed as odds ratios and 95% CIs.

^*p<0.001.

CI, confidence interval.

Associations that meet the threshold for statistical significance (alpha-level = 0.05) are shown in boldface.