Morbidity associated with cesarean delivery in the United States: is placenta accreta an increasingly important contributor?




Materials and Methods


We used 2000-2011 data from the Nationwide Inpatient Sample, which is the largest all-payer hospital inpatient care database in the United States and is maintained by the Agency for Healthcare Research and Quality as part of its Healthcare Cost and Utilization Project. The Nationwide Inpatient Sample is a stratified sample of approximately 20% of all community hospitals in the United States and includes all discharges from an average of 1000 hospitals each year. Thus, when weights are applied during analysis to account for the complex survey design, nationwide estimates can be derived. Each discharge record has the potential to list up to 15 International Classification of Disease , 9th Revision, Clinical Modification (ICD-9-CM) diagnoses and 15 ICD-9-CM procedures as well as diagnosis-related group codes. Because this analysis used publicly available data lacking personal identifiers, the Centers for Disease Control and Prevention’s Institutional Review Board determined it to be research that does not involve human subjects.


We identified all delivery hospitalization records using the algorithm developed by Kuklina et al. This algorithm uses ICD-9-CM diagnosis codes for delivery outcomes, ICD-9-CM procedure codes for selected delivery-related procedures, and diagnosis-related group delivery codes. Cesarean deliveries were identified by the presence of an ICD-9-CM procedure code for cesarean delivery (74.0, 74.1, 74.2, 74.4, 74.99). Among cesarean deliveries, those with an ICD-9-CM diagnosis code 654.2 were classified as repeat cesarean deliveries and those without such code were considered primary cesarean deliveries. We used the ICD-9-CM diagnosis or procedure codes shown in Table 1 to identify records with the following 11 complications or conditions that potentially are associated with cesarean delivery: (1) urinary bladder operations, (2) cystotomy, (3) anesthesia complications, (4) obstetric wound complications, (5) blood transfusion, (6) ventilation support, (7) renal failure, (8) sepsis, (9) shock, (10) prolonged hospital stay defined as stay longer than five days (ie, 90th percentile of the length of hospital stay distributions for all cesarean deliveries in the sample), and (11) death during the delivery hospitalization.



Table 1

ICD-9-CM codes for cesarean delivery complications and chronic conditions examined in the analysis





























































Condition Diagnosis or procedure codes
Cesarean delivery complications
Urinary bladder operations 57.x
Cystotomy 57.1
Anesthesia complications 668.0x, 668.1x, 668.2x
Blood transfusion 99.0x
Ventilation support 93.90, 96.01-96.05, 96.7x
Renal failure 669.3, 584.x
Sepsis 038.0-038.4, 038.8, 038.9, 995.91, 995.92
Shock 669.1, 998.0, 995.0, 995.4, 785.5x
Obstetric wound complications 674.10, 674.12, 674.14, 674.30, 674.32, 674.34
Chronic conditions
Preexisting diabetes mellitus 249.x, 250.x, 648.0x
Chronic hypertensive disease 401.x-405.x, 642.0x, 642.1x, 642.2x, 642.7x
Chronic heart disease 412.x, 413.x, 414.x, 394.x, 395.x, 396.x, 397.x, 424.x, 428.22, 428.23, 428.32, 428.33, 428.42, 428.43
Chronic respiratory disease 491.x-496.x
Chronic renal disease 581.x-583.x, 585.x, 587.x, 588.x, 646.2x
Chronic liver disease 571.x, 572.x
HIV/AIDS 042.x, V08.x

ICD-9-CM, International Classification of Disease , 9th Revision, Clinical Modification.

Creanga. Cesarean delivery morbidity in the United States. Am J Obstet Gynecol 2015 .


In addition, of special interest for this analysis was the identification of records from patients with placenta accreta, since this condition poses serious maternal risks in pregnancies after a cesarean delivery and contemporary national-level data on this condition are lacking. Because there is no specific ICD-9-CM code for placenta accreta, we developed and validated an ICD-9-CM code–based algorithm to identify diagnoses and procedures that, when concurrently coded and in the absence of uterine rupture (ICD-9-CM codes: 665.0x, 665.10, 665.11), identify placenta accreta with a high positive predictive value among women with a previous cesarean delivery. This algorithm identified patients with a diagnosis of placenta previa (ICD-9-CM codes: 641.0, 641.1) or retained placenta (ICD-9-CM codes: 666.0, 667.x), and a hysterectomy procedure code (ICD-9-CM codes: 68.3, 68.4, 68.5, 68.6, 68.7, 68.8, 68.9). Specifically for this analysis, this algorithm was validated at the Massachusetts General Hospital and the Stanford University School of Medicine by a comparison of recorded ICD-9-CM codes in administrative hospital data against medical record data for the periods between Jan. 1, 2001, to Dec. 31, 2011, and Jan. 1, 2000, and Dec. 31, 2013, respectively. Validation exercises were approved by Institutional Review Boards at Partner’s Healthcare and Stanford University, respectively. The medical record review was conducted by 2 obstetrics anesthesia residents (A.M. and L.R.), 1 at each validation site. Of the 15 probable accreta cases at Massachusetts General Hospital and 54 probable accreta cases at Stanford University that were identified based on our ICD-9-CM code algorithm, 14 and 47 cases, respectively, were confirmed by 1 of the following items: (1) radiologic evidence, (2) a presumptive clinical diagnosis made surgically during cesarean delivery or laparotomy after vaginal delivery, (3) pathology report, or (4) a description in the patient discharge summary that was written by the obstetrician. The 2-site positive predictive value of our ICD-9-CM–based accreta algorithm in women with a previous cesarean delivery was 88.4% (95% confidence interval [CI], 78.4–94.6). For consistency among all analyses that were performed, we used the same algorithm to identify accreta cases among women with a primary cesarean delivery.


We first examined trends in primary and repeat cesarean delivery between 2000 and 2011. Next, we used pooled 2000-2011 data to estimate rates for each of the 11 complications or conditions noted earlier, placenta accreta that was identified with our validated ICD-9-CM–based algorithm, and a composite cesarean delivery morbidity measure that included at least 1 of these 12 conditions by type of cesarean delivery: primary vs repeat. Also by type of cesarean delivery, we examined rate differences and percentage rate changes between 2000 and 2011 for each of the 12 conditions and for the composite cesarean delivery morbidity measure. On the pooled dataset, we fitted year-adjusted Poisson regression models to assess the relative incidence of each of the 12 conditions and of the composite cesarean delivery morbidity measure among repeat vs primary cesarean deliveries; incidence rate ratios (IRRs) and corresponding 95% CIs were estimated.


Characteristics of women without cesarean delivery complications, those with placenta accreta, and those with at least 1 of the 12 conditions examined in each of the 2 groups (primary vs repeat cesarean deliveries) were examined with chi square tests; similarly, we assessed characteristics of the hospitals where cesarean deliveries were obtained during the study period. The maternal characteristics examined were age (15-19, 20-24, 25-29, 30-34, ≥35 years); race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, Asian, American Indian or Alaska native, other); insurance coverage for delivery (Medicaid, private, self-pay, other); household income quartile for patient by ZIP code; and presence of at least 1 of the following chronic medical conditions: preexisting diabetes mellitus, chronic hypertensive disease, chronic heart disease, chronic respiratory disease, chronic renal disease, chronic liver disease, and HIV/AIDS (the corresponding ICD-9-CM codes are shown in Table 1 ). The hospital characteristics examined were location (urban/rural), teaching status (yes/no), ownership (public, private for-profit, private not-for-profit), bed size (small, medium, large), and total hospital charges as submitted by each hospital and reported in 2011 US dollars after adjustment for inflation with the use of the Consumer Price Indices that are released annually by the US Bureau of Labor Statistics. In separate models, we investigated factors that are associated with placenta accreta and composite cesarean delivery morbidity (defined by the presence of at least 1 of the 12 complications) by fitting multivariable Poisson regression models that are adjusted for all the patient and hospital characteristics mentioned earlier, except for hospital charges. All analyses were conducted in Stata software (version 13; StataCorp, College Station, TX) and were adjusted for the complex survey design of the Nationwide Inpatient Sample.




Results


The percentage of all hospital deliveries in the United States that were cesarean deliveries increased significantly from 22.8% in 2000 to 33.3% in 2011, with a peak at 33.6% in 2009 ( P < .05; Figure 1 ). The increase was steeper for repeat (8.7% in 2000 vs 15.3% in 2011; P < .05) than for primary (14.2% in 2000 vs 18.0% in 2011; P < .05) cesarean deliveries. Moreover, the increase in repeat cesarean deliveries was monotonic from 2000-2011; the percentage of all deliveries that were primary cesarean deliveries peaked at 18.6% in 2009.




Figure 1


Trends in primary and repeat cesarean delivery: Nationwide Inpatient Sample, United States, 2000-2011

Statistical significance of rate trends was assessed with the use of the Cuzick test-for-trend.

Creanga. Cesarean delivery morbidity in the United States. Am J Obstet Gynecol 2015 .


From 2000-2011, approximately 76 in 1000 cesarean deliveries (97 in 1000 primary cesarean deliveries and 48 in 1000 repeat cesarean deliveries) were accompanied by at least 1 of the 12 conditions of interest; of these, approximately three-quarters of primary cesarean deliveries and approximately one-half of repeat cesarean deliveries were associated with a hospital stay of >5 days ( Table 2 ). The prevalence of 5 specific medical complications (renal failure, need for ventilation support, urinary bladder operations, obstetric wound complications, and need for blood transfusion) was greater than 1 per 1000 primary cesarean deliveries; notably, approximately 18 in every 1000 women with a primary cesarean delivery received a blood transfusion. Among repeat cesarean deliveries, placenta accreta, urinary bladder operations, obstetric wound complications, and blood transfusion had a prevalence of >1 per 1000 such deliveries; placenta accreta was associated with approximately 1.8 of 1000 repeat cesarean deliveries, and blood transfusion was part of clinical treatment for 13 of 1000 women with a repeat cesarean delivery during the study period.



Table 2

Morbidity associated with cesarean delivery: United States, 2000-2011






































































































































Type of morbidity Pooled 2000-2011
cases, n
Pooled 2000-2011
rate (standard error) a
2011 vs 2000
rate difference, (95% confidence interval) b
Adjusted-incidence rate ratio
(95% confidence interval) c
Primary cesarean deliveries (n = 8,560,005) Repeat cesarean deliveries (n = 6,317,911) Primary cesarean deliveries Repeat cesarean deliveries Primary cesarean deliveries Repeat cesarean deliveries
Cystotomy 292 729 0.17 (0.007) 0.56 (0.02) –0.04 (–0.12 to 0.05) –0.24 (–0.47 to –0.01) d 3.40 (3.20–3.62)
Death 448 93 0.25 (0.01) 0.07 (0.007) –0.07 (–0.20 to 0.05) –0.06 (–0.14 to 0.03) 0.29 (0.26–0.32)
Anesthesia complication 963 382 0.55 (0.02) 0.29 (0.01) –0.54 (–0.75 to –0.35) d –0.51 (–0.71 to –0.31) d 0.55 (0.52–0.58)
Placenta accreta 1178 2281 0.67 (0.02) 1.76 (0.04) –0.10 (–0.31 to 0.11) 0.45 (0.07–0.84) d 2.61 (2.53–2.70)
Shock 1228 559 0.70 (0.02) 0.43 (0.02) 0.74 (0.53–0.95) d 0.37 (0.19–0.55) d 0.60 (0.58–0.63)
Sepsis 1634 267 0.93 (0.02) 0.21 (0.01) –0.07 (–0.29 to 0.14) –0.17 (–0.30 to –0.03) d 0.22 (0.21–0.24)
Renal failure 2451 496 1.39 (0.03) 0.38 (0.02) 1.07 (0.79–1.35) d 0.37 (0.19–0.54) d 0.27 (0.26–0.28)
Ventilation support 3627 1022 2.06 (0.03) 0.79 (0.02) 0.27 (–0.08 to 0.61) 0.25 (–0.02 to 0.51) 0.38 (0.37–0.39)
Urinary bladder operation 5671 5014 3.22 (0.04) 3.86 (0.05) –0.12 (–0.57 to 0.33) –0.93 (–1.57 to –0.30) d 1.19 (1.17–1.21)
Obstetric wound complication 17,126 14,622 9.73 (0.07) 11.26 (0.09) –0.73 (–1.47 to –0.02) d –4.01 (–5.01 to –3.00) d 1.17 (1.15–1.18)
Blood transfusion 32,048 16,403 18.22 (0.10) 12.63 (0.10) 16.42 (15.44–17.44) d 12.04 (11.05–13.03) d 0.68 (0.67–0.68)
Prolonged hospital stay 129,207 31,615 73.44 (0.20) 24.33 (0.14) –8.54 (–10.57 to –6.51) d –7.09 (–8.55 to –5.62) d 0.33 (0.33–0.34)
≥1 complication listed 171,023 62,688 97.21 (0.22) 48.25 (0.19) 3.99 (1.69–6.28) d –1.63 (–3.66 to 0.39) 0.50 (0.49–0.50)

Creanga. Cesarean delivery morbidity in the United States. Am J Obstet Gynecol 2015 .

a Rates reported per 1000 deliveries


b Rate differences reported per 1000 deliveries


c Poisson regression models adjusted for type of cesarean delivery (primary cesarean delivery group used as reference) and year


d Statistically significant at P < .05.



The rate of the composite cesarean delivery morbidity increased by 3.6% ( P < .001; Figures 2 and 3 ) among women with a primary cesarean delivery but did not change significantly among those with repeat cesarean delivery from 2000-2011. The rate of placenta accreta increased significantly only among women with a repeat cesarean delivery, from 1.6 to 2.0 per 1000 repeat cesarean deliveries, a 30.8% increase during the same time period ( P = .025; Figures 2 and 3 ). Several significant complication rate changes stand out among women with both primary and repeat cesarean deliveries ( Figure 2 ). Between 2000 and 2011, rates of anesthesia complications, obstetric wound complications, and especially prolonged hospital stay decreased among women with both primary and repeat cesarean deliveries; rates of sepsis, cystotomy, and urinary bladder operations declined significantly only among women with a repeat cesarean delivery (all P < .05). Conversely, during the same period, the rates of shock, renal failure, and blood transfusion increased by 190.0%, 110.9%, and 154.3%, respectively, among women with primary cesarean deliveries and by 150.0%, 168.2%, and 164.6%, respectively, among women with repeat cesarean deliveries (all P < .05).




Figure 2


Percentage rate changes in morbidity associated with cesarean delivery complications: United States, 2000-2011

Percentage rate changes are statistically significant at a probability value of < .05, based on Stata pretests for equality of proportions except for the following events: cystotomy, in-hospital death, placenta accreta, sepsis, ventilation support, and urinary bladder operation among women with primary cesarean deliveries; in-hospital death, ventilation support, and ≥1 complications among women with repeat cesarean deliveries.

Creanga. Cesarean delivery morbidity in the United States. Am J Obstet Gynecol 2015 .



Figure 3


Trends in morbidity associated with cesarean delivery complications: United States, 2000-2011

Statistical significance of rate trends was assessed with the use of the Cuzick test-for-trend.

Creanga. Cesarean delivery morbidity in the United States. Am J Obstet Gynecol 2015 .


After controlling for year-to-year variations, we found that, when compared with women having a first cesarean delivery, those who obtained a repeat cesarean delivery were approximately one-half as likely (IRR, 0.50; 95% CI, 0.49–0.50) to have experienced at least 1 of the conditions of interest, but more likely to have had a cystotomy (IRR, 3.40; 95% CI, 3.20–3.62), placenta accreta (IRR, 2.61; 95% CI, 2.53–2.70), a urinary bladder operation (IRR, 1.19; 95% CI, 1.17–1.21), or wound complications (IRR, 1.17; 95% CI, 1.15–1.18); all other specific complications were significantly less prevalent in women with repeat rather than primary cesarean deliveries ( Table 2 ).


Overall, women with at least 1 cesarean delivery complication, and especially those with a repeat cesarean delivery, were older, in higher proportion black, insured by Medicaid, and with a chronic medical condition than were women without a cesarean delivery complication ( Table 3 ); they also had ≥2 additional diagnoses at discharge and more of their cesarean deliveries took place in urban, teaching, public facilities than in other types of facilities when compared with women without a cesarean delivery complication. Notably, median total hospital charges were overall lower for women with repeat ($10,866.50) than for women with primary ($12,547.70) cesarean deliveries who had no complications. For women with at least 1 cesarean delivery complication, median total hospital charges were more than double ($23,672.30 if primary and $19,033.00 if repeat cesarean delivery). Moreover, for women with placenta accreta, median total hospital charges were $34,035.50 if primary cesarean delivery and $33,944.1 if repeat cesarean delivery.



Table 3

Characteristic of primary and repeat cesarean deliveries: United States, 2000-2011















































































































































































































































































































































































































Characteristic Primary cesarean deliveries Repeat cesarean deliveries
No complication (n = 7,722,632) ≥1 complication (n = 837,373) Accreta (n = 5734) No complication (n = 5,996,357) ≥1 complication (n = 321,554) Accreta (n = 11,092)
Maternal characteristics, %
Age, y
15-19 10.6 10.9 0.7 2.3 2.3 0.6
20-24 22.9 21.6 6.5 17.8 16.0 7.0
25-29 26.3 23.8 17.0 26.9 24.6 17.3
30-34 23.8 23.4 28.6 30.2 29.2 32.9
>35 16.4 20.2 47.1 22.8 28.0 42.2
Race/ethnicity
Non-Hispanic white 42.6 37.9 39.4 40.7 35.4 35.7
Non-Hispanic black 10.8 16.8 12.3 10.6 17.7 12.4
Hispanic 16.6 15.6 19.0 21.0 19.6 27.3
Asian 4.0 3.6 6.0 3.3 3.0 3.4
American Indian or Alaska Native 0.5 0.7 0.5 0.6 0.7 0.6
Other 3.8 4.0 3.3 3.6 3.7 3.6
Missing 21.7 21.6 19.6 20.3 19.9 17.1
Insurance coverage
Medicaid 36.3 40.2 33.2 40.0 45.1 43.0
Private 57.7 53.3 60.3 53.5 47.4 50.4
Self-pay 2.6 2.6 3.5 3.1 3.3 2.7
Other 3.3 3.7 3.0 3.3 3.9 3.8
Missing 0.2 0.2 0.0 0.2 0.2 0.2
Income quartile for patient ZIP code
1st (lowest) 24.9 27.1 23.7 26.7 30.2 27.2
2nd 24.1 23.7 22.3 24.2 23.9 22.5
3rd 24.5 23.4 25.0 23.3 22.0 22.4
4th (highest) 24.8 23.7 27.0 24.0 21.7 25.4
Missing 1.7 2.1 1.9 1.7 2.2 2.4
Chronic conditions a
Yes 7.3 16.6 12.5 7.3 17.6 10.3
No 92.7 83.4 87.5 92.7 82.4 89.7
Hospital/hospitalization characteristics
Discharge diagnoses, mean ± standard deviation 5.1 ± 2.4 7.6 ± 3.2 8.9 ± 4.1 4.6 ± 2.3 7.8 ± 3.3 9.3 ± 3.8
Hospital procedures, mean ± standard deviation 1.9 ± 1.1 2.5 ± 1.6 4.5 ± 2.5 1.7 ± 0.9 2.6 ± 1.6 4.8 ± 2.4
Location, %
Urban 88.4 92.7 95.2 87.7 90.8 94.9
Rural 11.6 7.3 4.8 12.3 9.2 5.1
Teaching status, %
Teaching 45.5 62.7 68.2 43.9 59.2 66.5
Nonteaching 54.5 37.3 31.8 56.1 40.8 33.5
Ownership, %
Public 63.8 74.7 77.9 62.5 72.2 77.4
Private not-for-profit 21.5 16.1 13.2 21.8 16.5 13.8
Private for profit 14.7 9.2 8.9 15.7 11.3 8.8
Bed size, %
Small 10.5 7.9 6.5 10.7 8.2 5.8
Medium 25.9 22.7 22.2 26.0 23.7 23.6
Large 63.7 69.4 71.3 63.2 68.1 70.6
Hospital costs, median (interquartile range) b 12,547.9 (8833.0–17,767.4) 23,672.3 (15,002.2–38,609.3) 34,035.5 (18,624.6–67,803.6) 10,866.5 (7569.3–15,391.0) 19,033.0 (11,193.1–32,663.5) 33,944.1 (17,832.5–64,232.4)

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May 6, 2017 | Posted by in GYNECOLOGY | Comments Off on Morbidity associated with cesarean delivery in the United States: is placenta accreta an increasingly important contributor?

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