Evaluating perinatal mortality rates: effects of referral and case mix.
OBJECTIVE
To evaluate perinatal mortality rates as a method of auditing obstetric and neonatal care after account had been taken of transfer between hospitals during pregnancy and case mix.


METHODS
Case-control study of perinatal deaths.


METHODS
Leicestershire health district.


METHODS
1179 singleton perinatal deaths and their selected live born controls among 114,362 singleton births to women whose place of residence was Leicestershire during 1978-87.


METHODS
Crude perinatal mortality rates and rates adjusted for case mix.


RESULTS
An estimated 11,701 of the 28,750 women booked for delivery in general practitioner maternity units were transferred to consultant units during their pregnancy. These 11,701 women had a high perinatal mortality rate (16.8/1000 deliveries). Perinatal mortality rates by place of booking showed little difference between general practitioner units (8.8/1000) and consultant units (9.3-11.7/1000). Perinatal mortality rates by place of delivery, however, showed substantial differences between general practitioner units (3.3/1000) and consultant units (9.4-12.6/1000) because of the selective referral of high risk women from general practitioner units to consultant units. Adjustment for risk factors made little difference to the rates except when the subset of deaths due to immaturity was adjusted for birth weight.


CONCLUSIONS
Perinatal mortality rates should be adjusted for case mix and referral patterns to get a meaningful result. Even when this is done it is difficult to compare the effectiveness of hospital units with perinatal mortality rates because of the increasingly small subset of perinatal deaths that are amenable to medical intervention.
Clarke
M
M
Department of Epidemiology and Public Health, University of Leicester, Leicester Royal Infirmary.
Mason
E S
ES
MacVicar
J
J
Clayton
D G
DG
D016022:Case-Control Studies; D036861:Delivery, Obstetric; D003953:Diagnosis-Related Groups; D004739:England / Q000453:epidemiology; D005194:Family Practice; D005260:Female; D006760:Hospitalization; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D011247:Pregnancy; D011295:Prenatal Care; D012017:Referral and Consultation; D012307:Risk Factors