Linkage of four administrative datasets to examine blood transfusion in pregnancy

Currently collected hospital data records fact of transfusion, but lacks detail on quantity of blood transfused, and timing of transfusions. A number of administrative datasets collect information on blood transfusion including quantity and timing. Linkage of multiple datasources has the potential to give increase the depth of information available for researchers. This study aims to describe the linkage of four administrative datasets to identify transfusions among women giving birth in NSW and to describe the population represented by this linked data. Hospital, birth, blood issue and blood pack databases were linked to identify women receiving red blood cell transfusions in NSW between July 2006 and December 2010. Characteristics of the linked data population are compared with the population of all women giving birth, and births in public hospitals. Between July 2006-December 2010 there were 425,036 births in NSW hospitals, including 235,796 in a population with additional blood issue data available, of which, 4642(2%) received a transfusion. Hospitals supplying blood issue data were more likely to be larger urban or tertiary hospitals, and had a higher risk population than the state overall and public hospitals generally. Linkage of multiple data sources provides additional detail compared with hospital data alone, providing a wealth of data for researchers. The population identified through linkage differs from the overall birthing population, and to a lesser extent from women birthing in public hospitals. In some cases this may affect generalisability of research findings, but in other cases may be beneficial

Haemoglobin changes during pregnancy: a retrospective cohort study of consecutive pregnancies

NHMR

Trends and outcomes of postpartum haemorrhage, 2003-2011

Background: While rates of postpartum haemorrhage (PPH) have continued to rise, it is not clear if the association with other morbidity and transfusion has changed over time. This study explores the recent trend in postpartum haemorrhage and risk factors for transfusion and other severe adverse maternal outcomes following postpartum haemorrhage, stratified by mode of delivery. Methods: Linked birth and hospital data were used to examine ICD-10AM coded PPH and outcomes in maternal birth admission records, 2003-2011 in hospitals in New South Wales (NSW), Australia (N= 818,965 singleton pregnancies). Trends were calculated on the whole population, and among subgroups, and tested using the Cochran Armitage test for trend. Logistic regression models were developed separately for vaginal and caesarean births, and for a maternal morbidity composite indicator (excluding transfusion) and red cell transfusion. Adjusted odds ratios (aOR) for yearly change and 95% confidence intervals (CI) are presented. Adjustment included maternal (eg. age, country of birth) and pregnancy factors (eg. parity, interventions, pregnancy complications). Results: Overall, there was a significant increase in the PPH rate, from 6.1% in 2003 to 8.3% in 2011 (p<0.0001). Having accounted for maternal and pregnancy factors, there was no significant increase in morbidity among women delivering vaginally with a PPH (aOR for yearly change 0.97 (0.94-1.00); p=0.36), and a slight decrease among women delivered by caesarean section (aOR 0.96 (0.92-0.99); p<0.01). There was a slight increase in transfusions for vaginal births (aOR 1.02 (1.00-1.03); p<0.01), however there was no significant trend amongst caesarean births (aOR 0.99 (0.97-1.01); p=0.30). Conclusions: PPH has become more frequent, however this has not been associated with increased maternal morbidity. This suggests that the increase in PPH may represent fewer severe haemorrhages, well-managed haemorrhage or better recording of PPH.NHMRC, AR

Variation in hospital caesarean section rates for preterm births

Background: Evidence about optimal mode of delivery for preterm birth is lacking and there is thought to be considerable variation in practice. Objective: To assess whether variation in hospital preterm caesarean section rates (Robson Classification Group 10) and outcomes are explained by casemix, labour or hospital characteristics. Materials and Methods: Population-based cohort study in NSW, 2007-2011. Births were categorised according to degree of prematurity and hospital service capability: 26-31 weeks, 32-33 weeks and 34-36 weeks. Hospital preterm caesarean rates were investigated using multilevel logistic regression models, progressively adjusting for casemix, labour and hospital factors. The association between hospital caesarean rates, and severe maternal and neonatal morbidity rates was assessed. Results: At 26-31 weeks the caesarean rate was 55.2% (7 hospitals, range 43.4-58.4%); 50.9% at 32-33 weeks (12 hospitals, 43.4- 58.1%); and 36.4% at 34-36 weeks (51 hospitals, 17.4-48.3%). At 26-31 weeks and 32-33 weeks, 81% and 59% of the variation between hospitals was explained with no hospital significantly different from the state average after adjustment. At 34-36 weeks, although 59% of the variation was explained, substantial unexplained variation persisted. Hospital caesarean rates were not associated with severe maternal morbidity rates at any gestational age. At 26-31 weeks medium and high caesarean rates were associated with higher severe neonatal morbidity rates, but there was no evidence of this association ≥32 weeks. 3 Conclusion: Both casemix and practice differences contributed to the variation in hospital caesarean rates. Low preterm caesarean rates were not associated with worse outcomes.Australian National Health and Medical Research Council; Australian Research Counci

Variation in hospital caesarean section rates for women with at least one previous caesarean section: a population based cohort study

Background: Internationally, repeat caesarean sections (Robson Classification Group 5) make the single largest contribution to overall caesarean section rates and hospital-to-hospital variation has been reported. It is unknown if case-mix and hospital factors explain variation in hospital rates of repeat caesarean sections and whether these rates are associated with maternal and neonatal morbidity. Methods: This population-based record linkage study utilised data from New South Wales, Australia between 2007 and 2011. The study population included all maternities with prior caesarean section that were singleton, cephalic and at term. Multilevel regression models were used with primary outcomes of ‘planned repeat caesarean section’ and ‘intra-partum caesarean section’. The associations between quintiles of risk-adjusted hospital rates of planned and intra-partum repeat caesarean sections and case-mix adjusted maternal and neonatal morbidity rates, postpartum haemorrhage rates and Apgar score below 7 at five minutes rates were also assessed. Results: Of 61894 maternities with a prior caesarean section in 81 hospitals, 82.1% resulted in a repeat caesarean section and 17.9% in vaginal birth. Of the caesarean sections, 72.7% were planned and 9.4% were unplanned intra-partum. Crude hospital rates of planned caesarean sections ranged from 50.7% to 98.4%. Overall 49.0% of between-hospital variation in planned repeat caesarean section rates was explained by patient characteristics (17.3%) and hospital factors (31.7%). Increased odds of planned caesarean section were associated with private hospital status and lower hospital propensity for vaginal birth after caesarean. There were no associations between quintiles of planned repeat caesarean section and adjusted morbidity rates. Crude rates of intra-partum caesarean section ranged from 12.9% to 71.9%. In total, 27.5% of between hospital variation in rates of intra-partum caesarean section was explained by patient (19.5%) and hospital factors (8.0%). The adjusted morbidity rates differed among quintiles of hospital intra-partum caesarean section rates, but were influenced by a few hospitals with outlying rates. 3 Conclusions: About half of the variation in hospital planned repeat caesarean section rates was explained and strategies aimed at modifying these rates should not affect morbidity rates. Intra-partum caesarean sections were associated with morbidity but not in a systematic mannerNHMRC, AR