Objective
This population-based study aimed to compare the risk of postpartum hemorrhage (PPH) for patients who underwent cesarean section delivery (CS) with general vs spinal/epidural anesthesia.
Study Design
We identified 67,328 women who had live singleton births by CS by linking the Taiwan National Health Insurance Research Dataset and the national birth certificate registry. Multivariate logistic regression was carried out to explore the relationship between anesthetic management type and PPH.
Results
Women who received general anesthesia had a higher rate of PPH than women who received epidural anesthesia (5.1% vs 0.4%). The odds of PPH in women who had CS with general anesthesia were 8.15 times higher (95% confidence interval, 6.43–10.33) than for those who had CS with epidural anesthesia, after adjustment was made for the maternal and fetal characteristics.
Conclusion
The odds that women will experience cesarean PPH with general anesthesia are approximately 8.15 times higher than for women who undergo CS with epidural anesthesia.
Despite great advances in medical therapies and surgical techniques in recent decades, postpartum hemorrhage (PPH) remains an important medical issue for both developing and developed countries. The incidence of PPH has been estimated to range from 1.47-18% of all deliveries, depending on the definition and criteria that are used and on the regions or countries concerned. With worldwide impact, PPH is associated with severe maternal morbidity, which includes postpartum hysterectomy, sepsis, acute renal failure, and intensive care unit admission and is considered the leading cause of maternal death in both the developed and developing world. The economic burden that is associated with PPH starts with costs for minor morbidities, such as anemia, which has been associated with a 9-fold increase in blood transfusions, 33% longer average length of hospital stay, and 50% higher average total cost per hospitalization. The impact of PPH is so serious that it deserves further scrutiny.
With approximately 500-800 mL/min blood flow, which comprises approximately 17% of cardiac output that perfuses the maternal uterus at term, cesarean section delivery (CS) inevitably results in significant blood loss before the uterine musculature can contract around uterine spiral arteries and hysterotomies. Uterine atony, or failure of the uterus to contract after delivery, results in massive bleeding and is recognized as the most common cause of PPH. Factors that preclude normal uterine contraction (such as leiomyoma, previous CS, uterine rupture, and prolonged labor ) also contribute to the incidence of PPH. Abnormal placentation is implicated as another major category of PPH cause. Risk factors that have been identified include placenta previa, retained placenta, low-lying placenta, and placenta accreta. Maternal risk factors for PPH have been demonstrated to include maternal blood disorders (eg, idiopathic thrombocytopenia, disseminated intravascular coagulopathy ) , antepartum/intrapartum hemorrhage and transfusion, obesity, age over 35 years, hypertensive disorders, preeclampsia, and disorders of active labor with/without the induction of labor (ie, labor dysfunction occurs in the active phase of the labor, such as arrest dilation of cervix and arrest of fetus descending), or tocolysis. Studies have also verified some obstetric risk factors that contribute to the occurrence of PPH that include parity, gestational age, and macrosomia with/without the newborn infant being large for gestational age.
Anesthetic management of CS, which includes general anesthesia and spinal/epidural anesthesia, rarely has been studied for the risks that are associated with PPH and has been based on only a limited number of cases from single hospital datasets. Thus, the role of different types of anesthesia in PPH must be clarified further. In this study, we set out to compare the risk of PPH after CS for those who receive general vs spinal/epidural anesthesia, with the use of a 1-year nationwide dataset. We hypothesized that women who received general anesthesia would be at higher risk of PPH compared with women who received epidural anesthesia, because adverse uterine contraction and platelet function might be associated with general anesthesia.
Methods
Database
This study linked 2 nationwide population-based datasets. The first was the Taiwan National Health Insurance Research Dataset (NHIRD), which is available to scientists in Taiwan for research purposes. As of 2007, the NHIRD includes all medical claims data and registries for contracted medical facilities, board-certified specialists, and 22.6 million beneficiaries, which represent >98.4% of the island’s population. The NHIRD is 1 of the largest and most comprehensive nationwide population-based datasets available in the world, which offers a unique opportunity to examine how different types of anesthetic treatment for women who undergo CS affect the risk of PPH.
The second database was the national birth certificate registry that is supervised by the Ministry of the Interior in Taiwan. The data on birth certificates consists of both infant and parent birth dates, gestational week at birth, birthweight, sex, parity, place of birth, parental educational level, and maternal marital status. The mother’s unique personal identification numbers provided links between the NHIRD and birth certificate data, with assistance from the Bureau of Health Promotion, Department of Health, Taiwan. Because the NHIRD consists of deidentified secondary data that have been released to the public for research purposes, this study was exempt from full review by the Institutional Review Board.
Study sample
We identified 204,610 women who were pregnant and used prenatal care services between January 1, 2005, and December 31, 2005. Of these, 69,533 women had live singleton births by CS and were included in our study. We excluded those patients (n = 1609) who were diagnosed with antepartum hemorrhage (ICD-9-CM codes 641, 641.3, 641.8, and 641.9) or hemorrhage from placenta previa (ICD-9-CM code 641.1) to better examine the relationship between types of anesthetic management and PPH. We also excluded patients who took medications to stop contractions (n = 10 women) or to induce labor (exclusively includes patients who had no signs of labor and were over term or for whom there were some special medical reasons for induction; n = 586). Ultimately, 67,328 women were included in this study: 2433 women received general anesthesia, and the other 64,895 women received spinal/epidural anesthesia.
Variables of interest
In this study, the independent variable of interest was treated as a dichotomous category, according to whether a woman had received general anesthesia during delivery. The outcome variable was whether a woman had hemorrhage within 24 hours of delivery (ICD-9-CM codes 666.1, 666.10, 666.12, and 666.14). We did not include patients who had delayed (defined as hemorrhage that occurred >24 hours after giving birth) and secondary PPH (defined as excessive vaginal bleeding between 24 hours and 6 weeks after delivery; ICD-9-CM codes 666.2, 666.20, 666.22, and 666.24).
To assess the independent effect of different modes of anesthetic management on PPH, we also adjusted for a number of potential confounders that had been identified in previous studies in the regression modeling and included mother’s age and fetal parity. Parity consisted of 3 categories: 1, 2, and ≥3. We also took the following antepartum or intrapartum complications that may be related to PPH into consideration in the regression modeling: placenta previa without hemorrhage (ICD-9-CM code 641.01), placenta abruption (ICD-9-CM code 641.2), overdistended uterus (ICD-9-CM code 653.5), pregnancy-induced hypertension (ICD-9-CM code 642), prolonged labor (ICD-9-CM code 662), previous myomectomy (ICD-9-CM code 654.91), chorioamnionitis (ICD-9-CM code 658.4), placenta accreta (ICD-9-CM code 667.0), previous CS (ICD-9-CM code 654.21), and emergent CS.
Statistical analysis
We used the SAS statistical package (version 8.2; SAS System for Windows; SAS Institute, Cary, NC) to perform all analyses in this study. Pearson χ 2 tests were used to examine differences between women who received general anesthesia and those who received spinal/epidural anesthesia. Therefore, multivariate logistic regression analyses were carried out to explore the risk of PPH among women who undergo CS. Crude and adjusted odds ratios (ORs) are presented with 95% CI. Variables that were significant at the level of < .1 in the bivariate analyses were recruited in the multivariate logistic regression models. A 2-sided probability value of < .05 was considered statistically significant for this study.
Results
Table 1 presents the distribution of characteristics of mothers and infants, according to the methods of anesthesia. Mothers who received general anesthesia (mean age, 30.7 years) were likely to be older than mothers who received spinal/epidural anesthesia (mean age, 29.9 years; P < .001). Table 1 also shows that mothers who received general anesthesia had a greater tendency to have complications such as pregnancy-induced hypertension ( P < .001), placental abruption ( P < .001), myoma ( P < .001), previous myomectomy ( P < .001), placenta accreta ( P < .001), and emergent CS ( P < .001) and a lower tendency to have complications such as overdistended uterus ( P = .003), prolonged labor ( P < .001), and previous CS ( P < .001) compared with mothers who received spinal/epidural anesthesia. In addition, mothers who received general anesthesia were more likely to have preterm births ( P < .001) and low-birthweight infants ( P < .001) compared with mothers who received spinal/epidural anesthesia.
