Blood for transfusion is a limited, costly resource, and its use has specific risks.1,2 Internationally, this has led to increased efforts to reduce unnecessary blood use across many disciplines.3 Transfusion of red blood cells generally has decreased in Australia in recent years4; however, there is evidence of increasing rates of maternal red blood cell transfusion around childbirth.5 This trend has also been observed in the United States, Canada, Finland, and Ireland, particularly in the context of postpartum hemorrhage.6–12 Between 1998 and 2009 in the United States, there was a steep increase in transfusions during a delivery admission (from 0.3% to 1.0%).12 The obstetric blood transfusion rate in Australia in 2002 was 0.88%, which was higher than contemporaneous rates reported in other countries, including the United States (0.46% in 2003),7 Canada (0.63% in 2004),13 and Ireland (0.84% in 2003).11 Reasons for the higher rate are unknown, although they may relate to differences in data collection. Obstetric transfusions tend to be urgent, unpredictable, and occur in otherwise healthy women.14
A small number of population-based studies have identified risk factors for blood transfusion in the maternity setting, including mode of delivery, placenta previa, antepartum hemorrhage, anemia, multiple pregnancies, and the extremes of maternal age.10,15,16 Population data provide a valuable source of data for studies of trends and risk factors for uncommon outcomes such as transfusion.17 These studies typically look only at the birth admission and are unable to estimate the transfusion burden associated with antenatal and postpartum hospitalizations. Few studies have considered blood products other than red cells.
This study aims to explore recent trends in blood and blood product transfusion and the use of blood products throughout pregnancy and the postnatal period in women whose pregnancy ended in a registered birth (beyond 20 weeks of gestation). We also examine the risk factors for transfusion during the birth admission.
MATERIALS AND METHODS
The study population included women giving birth in New South Wales hospitals between January 2001 and December 2010. New South Wales is the most populous state in Australia, with more than 7 million residents and approximately 90,000 births per year. “Birth data” including maternal characteristics, pregnancy, and birth were obtained from the Perinatal Data Collection. The Perinatal Data Collection is a statutory population-based collection of all births in New South Wales of at least 20 weeks of gestation or 400 g birth weight. These data were linked to “hospital data” from the Admitted Patients Data Collection. The Admitted Patients Data Collection is a census of all hospital discharges in New South Wales and records information on diagnoses and procedures associated with these discharges. Up to 20 of the 55 available diagnoses and procedures for each discharge are coded according to the International Classification of Diseases, 10th Revision, Australian Modification and the Australian Classification of Health Interventions. The New South Wales Centre for Health Record Linkage performed probabilistic data linkage between the two data sets.18 For this study, rates of incorrect and missed links were less than 5 per 1,000.
Hospital admissions were classified as antenatal, birth, or postnatal to allow for examination of the different blood product use at each stage of pregnancy. Antenatal admissions were those that occurred from 20 weeks of gestation and ended with the mother being discharged before the birth. Birth admissions were separated into those with a prolonged antenatal component (greater than 4 days) and those admitted 4 days or less before delivery. Postnatal admissions were admissions occurring after the initial discharge of the mother but within 6 weeks of the birth. Admissions involving transfusion of blood products were identified from the hospital data using Australian Classification of Health Interventions procedure codes.19 “Blood transfusion” refers to the administration of packed red cells or whole blood and “platelets and coagulation factors” include platelets, coagulation factors, and other serum (including fresh-frozen plasma); “blood products” is used to refer to transfusion of either or both of these. Blood transfusion (sensitivity 83.1%, specificity 99.9%) and administration of platelets and coagulation factors (sensitivity 73.1%, specificity 100%) are well ascertained in the hospital data.17 The quality of reporting of use of other blood-derived products (including leukocytes, gamma globulin) is unknown and so use of these products was not considered. Women with iron deficiency anemia were identified from the hospital data and women with bleeding or platelet disorders were identified by International Classification of Diseases, 10th Revision, Australian Modification codes for conditions such as thalassemia, hemolytic and aplastic anemias, coagulation defects, and idiopathic thrombocytopenic purpura (see the Appendix, available online at http://links.lww.com/AOG/A454). Antepartum hemorrhage included placental abruption or other antepartum hemorrhage. Women without bleeding disorders, antepartum hemorrhage, placenta previa, hypertension, and diabetes were considered to have no prior indication for transfusions. Age and gestational age groups were determined based on clinical relevance and women were classified as private patients if they received private obstetric care in a public or private hospital.
Rates were calculated per 1,000 deliveries and proportions are proportion of deliveries unless otherwise specified. Multiple births (twins or higher-order multiples) were counted as a single delivery. Trends were assessed using the Cochran Armitage test for trend. Significance was set at α=0.01. A multivariable Poisson regression model with robust variances was used to identify factors associated with higher use of blood product transfusions; factors that were significant with α 0.2 in a univariate model were included in the initial multivariable model and removed in a stepwise fashion until only variables significant at α 0.01 remained. This was performed separately for vaginal and cesarean deliveries to account for possible differences in decision-making based on physical location (operating room compared with birth unit) and differing criteria for postpartum hemorrhage (a common indication for blood transfusion). In the International Classification of Diseases, 10th Revision, Australian Modification, postpartum hemorrhage is defined as blood loss of 750 mL or more after cesarean delivery or 500 mL or more after vaginal birth.20 Women with missing data for possible confounding factors were excluded from this analysis. All analyses were performed in SAS 9.3. Ethical approval was obtained from the New South Wales Population and Health Services Research Ethics Committee.
In the period 2001–2010, there were 891,914 deliveries to 578,207 women involving 1,117,939 admissions. The blood product transfusion rate was 1.4% (99% confidence interval [CI] 1.3–1.4) of deliveries with 11,529 mothers receiving a transfusion in 12,147 pregnancies or the postnatal period. During the time period, 286 women had more than one delivery involving a transfusion, including 50 (17%) women with a bleeding disorder. Blood products were transfused in 484 antenatal admissions, 667 prolonged birth admissions, 10,715 birth admissions, and 600 postnatal admissions. The transfusion rate was highest for the birth admission (12.0/1,000 deliveries) compared with the antenatal (0.5/1,000 deliveries), prolonged birth admissions (0.87/1,000 deliveries), and postnatal admissions (0.7/1,000 deliveries). Ninety-one percent (11,382) of transfusions occurred in the birth admission, whereas 3.9% were antenatal and 4.8% were postnatal transfusions.
The transfusion of blood products at any stage during pregnancy, birth, or the postnatal period increased steadily from 1.2% in 2001 to 1.6% in 2010 (P≤.001) (Fig. 1). When considering only birth admission, the rate increased from 11.0 per 1,000 in 2001 to 15.3 per 1,000 in 2010 (P<.001). There has been little change in the type of products used with the majority of women (86%) receiving only packed red cells, whole blood, or both, packed cells making up the majority of this (99.4%). There was a significant increase in the number of women receiving packed cells alone (P=.003) or in conjunction with other blood products (P<.001), but not in those receiving other products alone (P=.1). When compared with red cell use, platelets and coagulation factors were more commonly used among women aged 35 years and older, private patients, multiparous women, and those having a cesarean delivery (Table 1). Where blood product transfusion occurred during pregnancy, this usually occurred in a single admission (98.6%) with less than 0.4% of deliveries involving three or more admissions involving transfusions.
Rates of transfusion in the birth and postnatal period were high in women having a hysterectomy in the birth admission (896.2/1,000 such deliveries, n=439), in which blood products had been transfused antenatally (187.5/1,000, n=63) and when a postpartum hemorrhage occurred in the birth admission (135.3/1,000, n=8,388). In women with no prior indication, the transfusion rate was 9.5 per 1,000 deliveries (n=6,927). Among birth admissions with fewer than a 4-day antenatal stay involving transfusion, 80.8% included a hemorrhage diagnosis. Women who received transfusions in birth or postnatal admission were in the hospital longer than those who did not (median days [interquartile range] birth 5 [4, 5] compared with 3 [2, 5], postnatal 3 [2, 5] compared with 2 [0, 3]).
Full data on possible confounders were available for 885,389 deliveries (99.3%) and were included in our risk factor analysis. Overall, 28.1% of women delivered by cesarean (n=249,775). Considering all births after adjusting for maternal factors, forceps delivery was associated with the highest risk of transfusion of all modes of birth when compared with noninstrumental vaginal delivery followed by intrapartum cesarean delivery, vacuum delivery, and prelabor cesarean delivery (Table 2). Across both vaginal and cesarean deliveries, women with bleeding or platelet disorders or placenta previa were at increased risk of transfusion. Among vaginal births, forceps deliveries and multiple births were also associated with more than doubling of the risk of transfusion, whereas among cesarean deliveries, preterm births at less than 33 weeks of gestation and antepartum hemorrhage were associated with a more than doubling of risk. Nulliparous women were at greater risk of transfusion when delivering vaginally as were women with a previous cesarean delivery (Table 2).
When included in the model, iron deficiency anemia was associated with an increased risk of transfusion (vaginal: number transfused=344, relative risk 7.1 [6.2–8.2]; cesarean: n=258, relative risk 4.7 [3.7–5.8]), leaving other estimates largely unchanged. However, identification of women with iron deficiency anemia has low sensitivity (5.7–12.0%)21 and so this was excluded from the final model.
Transfusion of blood or blood products occurred in one in every 71 deliveries in New South Wales between 2001 and 2010 with the majority of these related to hemorrhage. The majority of transfusions occurred during the birth admission, which is unsurprising given the large proportion associated with postpartum hemorrhage, which typically occurs within 24 hours after birth. The transfusion rate among women with no prior indication for blood transfusion was 1.0%, indicating that transfusion in otherwise healthy women is not uncommon.
Over the last 10 years there has been a 33% increase in the use of blood and blood products throughout pregnancy. Obstetric patients use a small proportion of the blood supply overall (3–4%)22; however, there is potentially increasing demand in this subpopulation at a time when resources are becoming more limited.1 One possible explanation for the increase is the changing maternal population with more older mothers, women with previous cesarean deliveries, and having more comorbid conditions6,11; however, we found that the trend persisted when changes in these factors were taken into account. Similarly, Kuklina et al7 found the increasing trend in transfusion between 1998 and 2005 in the United States persisted despite adjustment for confounders.
Another possible reason for the increase in transfusion is the recent increase in postpartum hemorrhage, which has been observed both in New South Wales23 and internationally.6,8,11,13 Because the majority of transfusions are performed in admissions with a diagnosis of hemorrhage, an increase in postpartum hemorrhage would likely lead to an increase in blood transfusions as has been observed elsewhere.8,9 The increase in transfusion is also possibly linked to increased severity of postpartum hemorrhage.9,11
The increase in transfusion rates may also reflect a change in practice with clinicians using less restrictive criteria for transfusion than in the past. We were unable to assess changes in transfusion thresholds; however, given the growing awareness of risks and costs associated with transfusion,1,2 it would be expected that changing practice would reduce transfusion rates. Interestingly, the slight dip in transfusion rates in 2008 coincided with a statewide initiative to decrease obstetric transfusions24; however, this decline was not maintained.
Risk factors identified in this study were consistent with previous studies.10,16,25–27 Of note, vaginal birth after cesarean delivery carried a higher risk of transfusion than repeat cesarean delivery,10,16,27 and cesarean and instrumental delivery had a higher risk of transfusion than noninstrumental vaginal delivery.10,16,26 Higher rates of transfusion were found for preterm deliveries26 and are possibly related to anemia, which is a risk factor for both preterm birth and transfusion.28
We found the rate of transfusion to be much lower in private hospitals compared with public, which is consistent with lower-risk women giving birth in appropriate settings.29–31 In Australia, tertiary obstetric care is only available in public hospitals. Tertiary hospitals had the highest rates of transfusion of platelets and coagulation factors, which may reflect increased complexity of cases in these hospitals or better access to products in the larger centers.
This study reflects the population burden of blood and blood product use in obstetrics in Australia. The use of longitudinally linked data allowed for the examination of blood product use within pregnancy. Validated and reliably collected information was available. The large number of women in the sample allowed for adjustment by a range of risk factors. Administrative data sets however lack clinical detail such as quantity of blood transfused, indication for transfusion, and hemoglobin measurements, which would provide insight into the severity of patients requiring transfusion.
Obstetric transfusion represents a small proportion of overall blood use; however, use of blood in obstetrics is rising and there is potential for this to continue as postpartum hemorrhage rates continue to increase. Because it has not been possible in this study to determine the exact indications and “triggers” for red cell transfusions, it is difficult to opine as to the appropriateness of many of the transfusions. Clearly, in exsanguinating hemorrhage, transfusion is essential and a life-saving measure with questions revolving more around hemodynamic and coagulopathic parameters. On the other hand, in hemodynamically stable patients in whom hemorrhage has been controlled or is not the problem, the issues of patient blood management and transfusion are different. Some reduction in transfusion rates may be possible through increased awareness of transfusion risk factors and treatment of anemia during pregnancy and adherence to principles of patient blood management. Additional reduction in blood use may be achievable through exploring variation in blood use between hospitals.
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