Table 1

Details of quality and safety indicators

Indicator	Rationale	Definition*	Exclusions
Maternal
Perineal tear	Third and fourth degree tears during vaginal delivery are not all preventable, but risk can be reduced through appropriate labour management and care standards¹⁷	Admission includes both diagnosis (ICD-10: O702-3) and procedure code (OPCS: R322, R325)	Caesarean sections
Puerperal infection	Puerperal sepsis can be associated with poor care (especially hygiene) at time of birth¹⁸	Admission includes diagnosis code for puerperal sepsis (ICD-10: O85-6) within 42 days of birth	None
Three day emergency readmission (all cause)†	Readmission rates have previously been shown to be associated with hospital care provided¹⁹	Emergency inpatient admission within 3 days, for which “admission source” field does not suggest transfer from other provider	Births for which discharge date is in final month of year covered in data year (March)
Neonatal
In-hospital perinatal mortality	Rate of still births plus in-hospital deaths within 7 days is associated with how hospital care is provided²⁰	Value suggesting stillborn in birth status (2, 3, 4) or discharge fields (5), and discharged within 7 days with discharge method (4) suggesting death	None
Injury to neonate	Although rare, birth trauma to neonate is often preventable²¹	Injury diagnosis code within admission (ICD-10: P102-4, P108-12, P114-5, P119, P122, P130-1, P138-9, P142, P148-9, P15)	Premature births, as identified through diagnosis code (ICD-10: P070-3), gestational age (<28 weeks), or birth weight (<2.5 kg)
			Injury of skeleton (osteogenesis imperfecta diagnosis, ICD-10: Q780)
			Stillborn babies
Selected neonatal infections	Neonatal infection is associated with poor care (especially hygiene) at time of birth¹⁸	Diagnosis procedure code (ICD-10: P36, P372/5/8-9, O753, O85-6, A41, A32, A49) within 3 days	Premature births, as identified through diagnosis code (ICD-10: P070-3), gestational age (<28 weeks), or birth weight (<2.5 kg)
Selected neonatal infections			Stillborn babies
Three day emergency readmissions (all cause)†	Readmission rates have previously been shown to be associated with how hospital care is provided²²	Emergency inpatient admission within 3 days, for which “admission source” field does not suggest transfer from other provider	Births for which discharge date is in final month of year covered in data year (March)
			Missing birth discharge date (~1% of births)
			Death during birth admission

*Discharges meeting inclusion/exclusion criteria for denominator. Records extracted according to the following case ascertainment rules. Delivery episodes: valid delivery method in either procedure (OPCS R17-R25 in any of the operation/procedure fields) or delivery method recorded in the maternity tail (delmeth=0-9); birth episodes: episode type recorded as 3 or 6 or admission methods recorded as 82 or 83.

†Literature review identified longer time periods for readmission rates; however, for purpose of this day of the week study, three day rates were used in keeping with suggestion that it is a more appropriate timeframe to evaluate association between day of admission and mortality.^{6 31}