Placenta Accreta Rates Reflect High Cesarean Rates and VBAC Bans

October is Accreta Awareness Month. The International Cesarean Awareness Network (ICAN) is featuring Accreta Awareness as part of its focus this month, and is promoting the importance of donating blood in order to help women who experience accretas.

Placenta Accreta is a condition in which the placenta attaches too deeply to the uterine wall, or actually grows into the uterine wall. Occasionally it even grows through the uterine wall and into adjoining tissues. This means the placenta can't separate during birth. It causes massive bleeding, and frequently requires a hysterectomy in order to control the bleeding. Placenta Accreta has about a 7% maternal mortality rate and is one of the most serious obstetric situations a woman can face.

You can read more about Placenta Accreta in my series about it here:

• Part One: What Is Accreta?
• Part Two: Life-Threatening Complication of Prior Cesarean
• Part Three: Risks to Mother and Baby
• Part Four: Diagnosis, Treatment, and a Cautionary Story

Accretas have several different risk factors, including maternal age, parity, smoking, infection, pregnancy after fertility treatment, and prior uterine procedures such as D&C or fibroid removal.

However, the strongest risk factor for accretas is a history of prior cesarean sections. The discovery of placenta previa (a low-lying placenta) in a woman with a history of prior cesareans is particularly predictive of an accreta.

In addition, the risk for accreta rises strongly as the number of prior cesareans increases. Silver 2006 found the following risk for accreta by number of prior cesareans:

• First cesarean:                  0.24%
• Second cesarean:             0.31%
• Third cesarean:                0.57%
• Fourth cesarean:              2.13%
• Fifth cesarean:                 2.33%
• Sixth or more cesarean:   6.74%

A recent large Nordic study found:

The risk of AIP [abnormally invasive placenta] increased seven-fold after one prior caesarean section (CS) to 56-fold after three or more CS.

Accretas are associated with poor outcomes, but very high-order repeat cesareans are particularly associated with poor outcomes.

Many accretas occur in women who have a cesarean in their first pregnancy and are automatically scheduled for repeat cesareans thereafter. Women who have larger families are particularly impacted. Yet many of these women say that they were never counseled about the risk of accreta with repeat cesareans. This is wrong. Informed consent should include discussions of all the risks of both VBAC and repeat cesareans.

Alarmingly, the incidence of placenta accreta cases seems to be on the rise. As noted by ACOG in the graphic above, this is likely in response to the rising cesarean rates. This reflects an increase in both primary cesareans and routine repeat cesareans as a result of de facto VBAC bans.

The increase in accretas is not just a U.S. phenomenon. A recent study from Hong Kong, where there is a high underlying cesarean rate, demonstrates that the rate of accreta increased over time as the cesarean rate increased. The authors note:

The overall rate of morbidly adherent placenta...increased from 0.17/1000 births in 1999-2003 to 0.79/1000 births in 2009-2013.

For such a rare condition, that's a significant increase. A similar result was found in an Italian region with a strong increase in cesarean rates over the years. Researchers found that:

The incidence increased from 0.12% during the 1970s, to 0.31% during the 2000s. During the same period, cesarean section rates increased from 17 to 64%. Prior cesarean section was the only risk factor showing a significant concomitant rise. Our results reinforce cesarean section as the most significant predisposing condition for placenta accreta.

One recent analysis concluded:

The incidence of placenta accreta has increased 13-fold since the early 1900s and directly correlates with the increasing cesarean delivery rate.

Alarmingly, the increase in accreta rates also seems to parallel the rise in maternal mortality rates over time. There are many other factors that play into the maternal mortality rate, mind, but the high cesarean rate and resulting accretas is one major piece of the puzzle.

If we hope to reduce the number of women impacted by accretas, we must reduce the cesarean rate. The authors of the recent Nordic study pointed this out, saying:

Our findings indicate that a lower CS rate in the population may be the most effective way to lower the incidence of AIP [Abnormally Invasive Placenta]. 

This means not only reducing the number of women who have first cesareans but also the number of women who have automatic repeat cesareans. In order to do that, we must increase access to VBACs. Far too many women have difficulty finding providers who will support them in labor after cesarean. Many hospitals have outright VBAC bans.

Of course, it's only fair to note that most women who have higher-order cesareans will not experience an accreta. However, accreta is such a serious and life-threatening condition that even relatively small incidences carry a huge burden of complications, cost, and potential loss of life. That's why it is vital that women have balanced risk counseling after a prior cesarean and real access to VBAC if they want it.

There are many birth stories online of women who have experienced accretas. It's important to emphasize that many of them have good outcomes, but also important to point out that many of them have challenging outcomes, and some of them have even had tragic outcomes.

This is the bottom line. Real women have died because of accretas, leaving their children motherless. Others have lost their uterus to hysterectomy or their babies to prematurity. Although I have not personally known anyone who died from accreta, I have known several women who have had very close near-misses due to accreta. Nearly all lost their uteri as a result of their accreta, and some lost their babies as well.

This is the real consequence of a too-high cesarean rate. This is why it's so important to avoid non-indicated cesareans and improve VBAC access. 

*If you can, give blood to help support women who have been affected by accreta. 


References

Support Groups

• http://www.hopeforaccreta.org/
• https://www.facebook.com/hopeforaccreta/
• http://www.circleofmoms.com/survivors-of-placenta-accreta-increta-or-percreta 
• http://community.babycentre.co.uk/groups/a3859975/placenta_accreta_support

Accreta Studies

Semin Perinatol. 2012 Oct;36(5):315-23. doi: 10.1053/j.semperi.2012.04.013. Implications of the first cesarean: perinatal and future reproductive health and subsequent cesareans, placentation issues, uterine rupture risk, morbidity, and mortality. Silver RM. PMID: 23009962

Rates of cesarean delivery have substantially increased worldwide during the past 30 years. Indeed, almost one-third of deliveries in the United States are cesareans. Most cesareans are safe, and major complications are uncommon. However, there is a "concealed" downside to cesarean deliveries. There are rare but life-threatening morbidities that may occur, which are often overlooked because most cesareans go well. In addition, subsequent pregnancies are fraught with an increased risk of both maternal and fetal complications. The worst of these are associated with placental problems such as previa, abruption, and accreta. The risk dramatically worsens in patients with multiple repeat cesarean deliveries. This article will summarize and highlight the implications of the rising cesarean rate on maternal and fetal morbidity and mortality.

Hong Kong Med J. 2015 Dec;21(6):511-7. doi: 10.12809/hkmj154599. Epub 2015 Nov 6. Rising incidence of morbidly adherent placenta and its association with previous caesarean section: a 15-year analysis in a tertiary hospital in Hong Kong. Cheng KK1, Lee MM1. PMID: 26554269

OBJECTIVES: To identify the incidence of morbidly adherent placenta in the context of a rising caesarean delivery rate within a single institution in the past 15 years, and to determine the contribution of morbidly adherent placenta to the incidence of massive postpartum haemorrhage requiring hysterectomy. SETTING: A regional obstetric unit in Hong Kong. PATIENTS: Patients with a morbidly adherent placenta with or without previous caesarean section scar from 1999 to 2013. RESULTS: A total of 39 patients with morbidly adherent placenta were identified during 1999 to 2013. The overall rate of morbidly adherent placenta was 0.48/1000 births, which increased from 0.17/1000 births in 1999-2003 to 0.79/1000 births in 2009-2013. The rate of morbidly adherent placenta with previous caesarean section scar and unscarred uterus also increased significantly. Previous caesarean section (odds ratio=24) and co-existing placenta praevia (odds ratio=585) remained the major risk factors for morbidly adherent placenta. With an increasing rate of morbidly adherent placenta, more patients had haemorrhage with a consequent increased need for peripartum hysterectomy. No significant difference in the hysterectomy rate of morbidly adherent placenta in caesarean scarred uterus (19/25) compared with unscarred uterus (8/14) was noted. This may have been due to increased detection of placenta praevia by ultrasound and awareness of possible adherent placenta in the scarred uterus, as well as more invasive interventions applied to conserve the uterus. CONCLUSION: Presence of a caesarean section scar remained the main risk factor for morbidly adherent placenta. Application of caesarean section should be minimised, especially in those who wish to pursue another future pregnancy, to prevent the subsequent morbidity consequent to a morbidly adherent placenta, in particular, massive postpartum haemorrhage and hysterectomy.

Acta Obstet Gynecol Scand. 2013 Apr;92(4):457-60. doi: 10.1111/aogs.12080. Placenta accreta: incidence and risk factors in an area with a particularly high rate of cesarean section. Morlando M, Sarno L, Napolitano R, Capone A, Tessitore G, Maruotti GM, Martinelli P. PMID: 23347183

...The aim of this study was to investigate the change in the incidence of placenta accreta and associated risk factors along four decades, from the 1970s to 2000s, in a tertiary south Italian center. We analyzed all cases of placenta accreta in a sample triennium for each decade. The incidence increased from 0.12% during the 1970s, to 0.31% during the 2000s. During the same period, cesarean section rates increased from 17 to 64%. Prior cesarean section was the only risk factor showing a significant concomitant rise. Our results reinforce cesarean section as the most significant predisposing condition for placenta accreta.

Obstet Gynecol. 2015 Sep;126(3):654-68. doi: 10.1097/AOG.0000000000001005. Abnormal Placentation: Placenta Previa, Vasa Previa, and Placenta Accreta. Silver RM1. PMID: 26244528

Placental disorders such as placenta previa, placenta accreta, and vasa previa are all associated with vaginal bleeding in the second half of pregnancy. They are also important causes of serious fetal and maternal morbidity and even mortality. Moreover, the rates of previa and accreta are increasing, probably as a result of increasing rates of cesarean delivery, maternal age, and assisted reproductive technology....

BJOG. 2016 Jul;123(8):1348-55. doi: 10.1111/1471-0528.13547. Epub 2015 Jul 29. Abnormally invasive placenta-prevalence, risk factors and antenatal suspicion: results from a large population-based pregnancy cohort study in the Nordic countries. Thurn L, Lindqvist PG, Jakobsson M, Colmorn LB, Klungsoyr K, Bjarnadóttir RI, Tapper AM, Børdahl PE, Gottvall K, Petersen KB,Krebs L, Gissler M, Langhoff-Roos J, Källen K. PMID: 26227006

OBJECTIVE: The objective was to investigate prevalence, estimate risk factors, and antenatal suspicion of abnormally invasive placenta (AIP) associated with laparotomy in women in the Nordic countries. DESIGN: Population-based cohort study. SETTING AND POPULATION: A 3-year Nordic collaboration among obstetricians to identify and report on uterine rupture, peripartum hysterectomy, excessive blood loss, and AIP from 2009 to 2012 The Nordic Obstetric Surveillance Study (NOSS). METHODS: In the NOSS study, clinicians reported AIP cases from maternity wards and the data were validated against National health registries. MAIN OUTCOME MEASURES: Prevalence, risk factors, antenatal suspicion, birth complications, and risk estimations using aggregated national data. RESULTS: A total of 205 cases of AIP in association with laparotomy were identified, representing 3.4 per 10 000 deliveries. The single most important risk factor, which was reported in 49% of all cases of AIP, was placenta praevia. The risk of AIP increased seven-fold after one prior caesarean section (CS) to 56-fold after three or more CS. Prior postpartum haemorrhage was associated with six-fold increased risk of AIP (95% confidence interval 3.7-10.9). Approximately 70% of all cases were not diagnosed antepartum. Of these, 39% had prior CS and 33% had placenta praevia. CONCLUSION: Our findings indicate that a lower CS rate in the population may be the most effective way to lower the incidence of AIP. Focused ultrasound assessment of women at high risk will likely strengthen antenatal suspicion. Prior PPH is a novel risk factor associated with an increased prevalence of AIP.

Am J Obstet Gynecol. 2015 Sep;213(3):384.e1-11. doi: 10.1016/j.ajog.2015.05.002. Epub 2015 May 5. Morbidity associated with cesarean delivery in the United States: is placenta accreta an increasingly important contributor? Creanga AA, Bateman BT, Butwick AJ, Raleigh L, Maeda A, Kuklina E, Callaghan WM. PMID: 25957019

OBJECTIVE: The purpose of this study was to examine cesarean delivery morbidity and its predictors in the United States. STUDY DESIGN: We used 2000-2011 Nationwide Inpatient Sample data to identify cesarean deliveries and records with 12 potential cesarean delivery complications, including placenta accreta. We estimated cesarean delivery morbidity rates and rate changes from 2000-2011, and fitted Poisson regression models to assess the relative incidence of morbidity among repeat vs primary cesarean deliveries and explore its predictors. RESULTS: From 2000-2011, 76 in 1000 cesarean deliveries (97 in 1000 primary and 48 in 1000 repeat cesarean deliveries) were accompanied by ≥1 of 12 complications. The unadjusted composite cesarean delivery morbidity rate increased by 3.6% only among women with a primary cesarean delivery (P < .001); the unadjusted rate of placenta accreta increased by 30.8% only among women with a repeat cesarean deliveries (P = .025). The adjusted rate of overall composite cesarean delivery morbidity decreased by 1% annually from 2000-2011 (P < .001). Compared with women with a primary cesarean delivery, those women who underwent a repeat cesarean delivery were one-half as likely (incidence rate ratio, 0.50; 95% CI, 0.49-0.50) to experience a complication, but 2.13 (95% CI, 1.98-2.29) times more likely to have a placenta accreta diagnosis. Both cesarean delivery morbidity and placenta accreta were positively associated with age >30 years, non-Hispanic black race/ethnicity, the presence of a chronic medical condition, and delivery in urban, teaching, or larger hospitals. CONCLUSION: Overall, cesarean delivery morbidity declined modestly from 2000-2011, but placenta accreta became an increasingly important contributor to repeat cesarean delivery morbidity. Clinicians should maintain a high index of suspicion for abnormal placentation and make adequate preparations for patients who need cesarean deliveries.

BJOG. 2013 Jan;120(1):85-91. doi: 10.1111/1471-0528.12010. Epub 2012 Oct 24. Multiple repeat caesarean section in the UK: incidence and consequences to mother and child. A national, prospective, cohort study. Cook JR1, Jarvis S, Knight M, Dhanjal MK. PMID: 23095012

OBJECTIVE: To estimate the incidence of multiple repeat caesarean section (MRCS) (five or more) in the UK and to describe the outcomes for women and their babies relative to women having fewer repeat caesarean sections. DESIGN: A national population-based prospective cohort study using the UK Obstetric Surveillance System (UKOSS). SETTING: All UK hospitals with consultant-led maternity units. POPULATION: Ninety-four women having their fifth or greater MRCS between January 2009 and December 2009, and 175 comparison women having their second to fourth caesarean section. METHODS: Prospective cohort and comparison identification through the UKOSS monthly mailing system. MAIN OUTCOME MEASURES: Incidence, maternal and neonatal complications. Relative risk, unadjusted (OR) and adjusted (aOR) odds ratio estimates. RESULTS: The estimated UK incidence of MRCS was 1.20 per 10 000 maternities [95% confidence interval (CI), 0.97-1.47]. Women with MRCS had significantly more major obstetric haemorrhages (>1500 ml) (aOR, 18.6; 95% CI, 3.89-88.8), visceral damage (aOR, 17.6; 95% CI, 1.85-167.1) and critical care admissions (aOR, 15.5; 95% CI, 3.16-76.0), than women with lower order repeat caesarean sections. These risks were greatest in the 18% of women with MRCS who also had placenta praevia or accreta. Neonates of mothers having MRCS were significantly more likely to be born prior to 37 weeks of gestation (OR, 6.15; 95% CI, 2.56-15.78) and therefore had higher rates of complications and admissions. CONCLUSIONS: MRCS is associated with greater maternal and neonatal morbidity than fewer caesarean sections. The associated maternal morbidity is largely secondary to placenta praevia and accreta, whereas higher rates of preterm delivery are most likely a response to antepartum haemorrhage.

Obstet Gynecol. 2011 Sep;118(3):687-90. doi: 10.1097/AOG.0b013e318227b8d9. The rising cesarean delivery rate in America: what are the consequences? Blanchette H1. PMID: 21860302

Cesarean delivery is now the most common operation in the United States, and it has increased dramatically from 5.8% in 1970 to 32.3% in 2008. This rise has not resulted in significant improvement in neonatal morbidity or maternal health. Three recent studies of elective repeat cesarean deliveries performed before 39 completed weeks of gestation have demonstrated increased respiratory and other adverse neonatal outcomes. Maternal mortality in the United States has increased from 10 per 100,000 to 14 per 100,000 from 1998 to 2004. Contributing to this in an increasing incidence of placenta accreta associated with multiple uterine scars requiring the need for emergency cesarean hysterectomy, blood transfusion, and maternal mortality due to obstetric hemorrhage. To reverse the trend of the rising cesarean delivery rate, obstetricians must reduce the primary rate and avoid the performance of a uterine incision unless absolutely necessary for fetal or maternal indications. For women with one previous low transverse cesarean delivery, obstetricians should promote a trial of labor after previous cesarean delivery in those women who desire three or more children.