Objective
The objective of the study was to assess risk factors for moderate and severe blood loss after cesarean delivery (CD).
Study Design
All planned (n = 32,716) and emergency (n = 47,942) cesareans, as reported over a 10-year period to the Medical Birth Registry of Norway, were analyzed separately in a case-control design. Women with moderate (500 to ≤1500 mL) or severe (>1500 mL) blood loss were analyzed with women with blood loss less than 500 mL as controls in SPSS (version 17.0) with χ 2 test and logistic regression.
Results
The prevalence of severe blood loss was consistently higher in emergency (3.2%) than planned CD (1.9%). Planned and emergency CDs share common risk factors for both moderate and severe blood loss, whereas emergency CD carries in addition delivery-related risk factors.
Conclusion
When revising management schemes for CD, anesthetic procedures should be reconsidered as surgical competence in cases with placenta previa, placental abruption, and low hemoglobin.
Worldwide, severe obstetric blood loss is one of the most important causes to maternal morbidity and mortality. The overall prevalence of severe obstetric blood loss varies by obstetric facility, the distribution of spontaneous vaginal to instrumental and cesarean deliveries (CDs), endpoint definition, case-ascertainment, quality of clinical management of complicated deliveries, and characteristics of the study populations. Combining data from spontaneous vaginal, instrumental, and CDs in studies on prevalence and risk factors of severe blood loss are improper because of the many clinical differences seen in pregnancy- and labor-related conditions that prevail through mode of delivery.
The indications and the many medical conditions differ in such a way that separate analyses on prevalence and risk factors for severe blood loss in planned and emergency surgery are necessary for understanding the results in relation to the clinical situation. From a literature search, we have identified only 2 of 8 relevant studies that distinguish between planned and emergency CDs when exploring risk factors for severe blood loss. As a consequence, our understanding of severe blood loss during CDs suffers from the lack of appropriate study designs, completeness, and the relevance of risk factors eligible for analysis.
The aim of this study was to examine prevalence and risk factors for moderate and severe blood loss in planned and emergency cesareans in Norway over a 10 year period.
Materials and Methods
With newborn as unit of notification, it has been compulsory to notify all births to the Medical Birth Registry of Norway (MBRN) since 1967. The case report form comprises information on maternal health before and during pregnancy, detailed information about the delivery, and information on immediate delivery-related complications in addition to information about the newborn. After the revision in 1998, specific information on moderate and severe blood loss has been available. In the present study, we included data from Jan. 1, 1999, through Dec. 31, 2008, as reported to MBRN.
Definition of study population
During the 10 year study period, 588,710 newborns were reported to the MBRN among 577,906 mothers. After exclusion of all mothers with vaginal deliveries (n = 491,017), mothers with triplets (n = 163), quadruplets (n = 12), and 10 women with invalid year of birth (n = 10), 86,704 mothers with CDs were susceptible for analysis. The CDs after failed forceps and/or vacuum and in placental abruption were denoted emergency CDs. Finally, 6046 mothers with unspecified CDs were excluded, leaving 32,716 and 47,942 women with planned or emergency CDs in singleton or duplex pregnancies, eligible for analysis.
Variable specification
Blood loss is reported to the MBRN in 4 categories: less than 500 mL (normal), 500-1500 mL (moderate), greater than 1500 mL (severe), bleeding amount greater than 500 mL not specified, or the need for blood transfusion coded as “yes” or “no” (“no” includes missing information). In the present study, bleeding amount greater than 500 mL not specified was categorized as 500-1500 mL (1.2% [379:32,716] in planned CD, 1.4%; [656:47,942] in emergency CDs), transfusion as severe blood loss, whereas missing data were coded by default less than 500 mL at data entry. Planned CD is defined as surgery taking place at least 8 hours after the decision, most often days in advance, whereas all other CDs are defined as emergency CD.
Explanatory variables were age (12-19, 20-29 [referent], 30-39, 40-54 years), parity (1, 2, 3 [referent], ≥4), previous stillbirths (≥0/1), and previous cesarean delivery (≥0/1). Smoking at end of pregnancy was reported as “no information” (includes no consent), none smoking, 1-9, or 10 or more cigarettes per day.
Bleeding during pregnancy was recorded on 4 variables (<13 gestational weeks, 13-28 weeks, >28 weeks, or overall). In the analyses we recoded bleeding during pregnancy to a “yes/no” response.
Chronic maternal diseases such as cardiac diseases, hypertension, diabetes mellitus, and epilepsy were categorized as “yes/no” responses. Pregnancy-related variables such as conception during assisted reproduction methods, plurality, pregnancy-induced hypertension, HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome, mild/moderate/severe preeclampsia, eclampsia, gestational diabetes mellitus, anemia during pregnancy (<9 g/L), placenta previa, and placental abruption were all categorized as “yes/no” (“no” includes missing information) responses as were labor-related variables such as transverse lie, failed vacuum/forceps extraction, induction (prostaglandins, oxytocin, amniotomy), and labor arrest (dystocia, prolonged labor, augmentation of labor, disproportionate pelvis, head deflection).
Birthweight was categorized into 4 groups (450-1499, 1500-2499, 2500-4499 [referent], and 4500-6500 g). Anesthesia was analyzed as spinal (referent), epidural, general anesthesia, or missing. We categorized hospital setting as university hospital and central hospital (referent) vs all others. Time period was categorized as 1999-2003 and 2004-2008 (referent).
Statistical analysis
Because of the many differences in maternal characteristics and pregnancy- and delivery-related conditions, we analyzed elective and emergency CD separately ( Table 1 ). All analyses were done in SPSS version 17.0 (SPSS Inc, Chicago, IL) with χ 2 test, χ 2 trend, or in forward stepwise logistic regression.
| Risk factor | Category | Planned CD | Emergency CD | P value (χ 2 ) |
|---|---|---|---|---|
| (n = 32,716) % | (n = 47,942) % | |||
| Blood loss | <500 mL | 69.3 | 65.2 | < .001 |
| 500-1500 mL | 27.7 | 30.3 | ||
| >500 mL unspecified | 1.2 | 1.4 | ||
| >1500 mL | 1.9 | 3.2 | ||
| Age, y | 13-19 | 0.9 | 2.1 | < .001 |
| 20-29 | 31.9 | 45.3 | ||
| 30-39 | 61.5 | 49.2 | ||
| 40-54 | 5.6 | 3.4 | ||
| Parity | 1 | 32.1 | 60.7 | < .001 |
| 2 | 39.9 | 26.0 | ||
| 3 | 21.2 | 9.6 | ||
| ≥4 | 6.8 | 3.8 | ||
| Previous CD, ≥1 | 42.5 | 17.5 | < .001 | |
| Previous stillbirths, ≥1 | 2.3 | 1.1 | < .001 | |
| Conception after assisted reproduction, yes | 3.4 | 3.6 | < .06 | |
| Duplex pregnancy, yes | 5.3 | 5.0 | < .11 | |
| Smoking at end of pregnancy | No information | 23.9 | 21.7 | < .001 |
| Not smoking | 66.1 | 67.9 | ||
| Sometimes | 1.1 | 1.0 | ||
| Daily | 8.8 | 9.4 | ||
| Bleeding in pregnancy | Before 13 gest. wks | 2.7 | 2.7 | < .87 |
| 13-28 gest. wks | 1.7 | 2.2 | < .001 | |
| After 28 gest. wks | 1.1 | 2.0 | < .001 | |
| In total | 5.0 | 6.2 | .01 | |
| Hgb <9.0 during pregnancy | 0.7 | 0.8 | < .49 | |
| Abruptio placentae | 0.0 | 4.0 | NA | |
| Placenta previa | 1.8 | 1.4 | < .001 | |
| Hypertension only | 1.9 | 2.2 | < .005 | |
| Preeclampsia | 5.2 | 12.8 | < .001 | |
| Eclampsia | 0.01 | 0.4 | < .001 | |
| HELLP syndrome | 0.09 | 1.3 | < .001 | |
| Induction of labor (failed induction) | Prostaglandins | 0.8 | 14.5 | < .001 |
| Oxytocin | 0.2 | 5.5 | < .001 | |
| Amniotomy | 0.1 | 4.5 | < .001 | |
| In total | 1.1 | 22.8 | < .001 | |
| Transverse lie | 2.2 | 2.0 | < .02 | |
| Labor arrest | 11.9 | 43.5 | .001 | |
| Failed vacuum/forceps (yes) | 0.0 | 2.3 | NA | |
| Anesthesia | No information | 3.2 | 3.2 | < .001 |
| Epidural | 8.0 | 21.1 | ||
| Spinal | 82.9 | 50.0 | ||
| General | 5.8 | 25.6 | ||
| Birthweight, g | <1499 | 1.5 | 5.2 | < .001 |
| 1500-2499 | 5.9 | 12.3 | ||
| 2500-4499 | 88.1 | 76.1 | ||
| >4500 | 4.5 | 6.5 | ||
| Time period | 1999-2003 | 45.7 | 48.3 | < .001 |
| 2004-2008 | 54.3 | 51.7 | ||
| Hospital setting | University hospital | 39.9 | 35.3 | < .001 |
| Central hospital | 23.8 | 27.3 | ||
| All others | 36.3 | 37.4 | ||
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