Placental Complications Increase With Prior Cesarean

April was Cesarean Awareness Month.  It was sponsored by The International Cesarean Awareness Network (ICAN), which seeks to help support women after cesareans, to raise awareness of the implications of a high cesarean rate, and to keep Vaginal Birth After Cesarean (VBAC) an accessible choice for women.

As a follow-up to Cesarean Awareness Month, let's discuss some of the possible complications of too many cesareans.

The importance of this discussion is highlighted this week by the recent tragic story of a woman who died from complications of Placenta Accreta during her sixth cesarean.

The fact is that each successive cesarean increases the risk for abnormal implantation of the placenta in future pregnancies, and this can be life-threatening to both mother and baby.

This is not to imply that all cesareans are bad; many are truly life-saving and necessary, and many others are probably prudent.  However, many non-indicated cesareans are being done these days. Cesareans are not without risks and this mother's death shows why they should not be done without good reason, especially multiple repeat cesareans.

The extremely high cesarean rates and lack of VBAC access in certain areas of this country and around the world has very distinct public health implications that should not be ignored.

One of those public health implications is the rising incidence of placenta previa and placenta accreta.  As one study summarized:

Placenta accreta is recognized as a catastrophic disease in obstetrics. Diagnosed incidentally, it has been a rare disease in previous decades prior [to] indiscriminate use of cesarean delivery. The World Health Organization has recently highlighted this disease as a new pandemic, which is directly related to patients who have two or more caesarean sections.

Abnormal Placentation

One of the most significant risks after having had a cesarean section is abnormal placental implantation in a future pregnancy.  There are several different types of these, which include:

• Placenta Previa (the placenta implants too low, near or over the cervix)
• Placenta Accreta (the placenta attaches abnormally and has difficulty detaching later)
• Placenta Increta (the placenta grows into the uterine muscle and has difficulty detaching)
• Placenta Percreta (the placenta grows through the uterus and into surrounding organs)

In addition, there is an increased risk of the placenta pulling away from the uterine wall prematurely (called placental abruption).  This, too, can be a serious complication.

Today we'll discuss overall increases in placental complications after prior cesareans; in later posts, we'll discuss each placental complication in more detail.

The big question is why a subsequent pregnancy after cesarean is at risk for placental issues.  Although the exact mechanism is not clear, most authorities agree that the damage to the lining of the uterus from a cesarean may predispose to placental implantation and/or detachment issues, especially if the fertilized egg implants near the scarred area.

Of course, it's not just cesareans; any damage to the lining of the uterus can predispose to placental issues.  A D&C procedure, whether after a miscarriage or to terminate a pregnancy, can cause problems with the uterine lining.  On the other hand, research differs on whether myomectomy (fibroid removal) does or does not have an association with placental issues.

Even such minor factors as uterine infection, smoking, drug or alcohol use, older age, or many pregnancies can predispose to placental implantation issues.  The theory is that they also damage the uterine lining, causing problems when the next pregnancy implants.

However, it's clear from research that one of the most powerful risk factors for placental issues is a prior cesarean, and that the risk increases as the number of prior cesareans increases.  This means that this condition is often iatrogenic (caused by the physician) and is a preventable risk in many cases.

Increase in Placental Complications

Research shows that the incidence of placental complications has risen in parallel with the burgeoning cesarean rate.

For example, one recent study on placenta accreta shows that

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

Another study that did a meta-analysis of the impact of multiple repeat cesareans found:

The incidence of placenta previa increased from 10/1000 deliveries with 1 previous cesarean delivery to 28/1000 with ≥3 cesarean deliveries. 

Now, keep in mind that most women with three or more cesareans still don't experience a previa. However, to increase from an incidence of 1% to 2.8% is a serious increase, given the risks associated with previas.

The authors of that meta-analysis also pointed out that women with previa who have had prior cesareans are at far greater risk for the very serious condition of Placenta Accreta than women with previa who have not had prior cesareans.

Compared with women with previa and no previous cesarean delivery, women with previa and ≥3 cesarean deliveries had a statistically significant increased risk of accreta (3.3-4% vs 50-67%), hysterectomy (0.7-4% vs 50-67%), and composite maternal morbidity (15% vs 83%; odds ratio, 33.6; 95% confidence interval, 14.6-77.4). 

In other words, the risk for having both previa and accreta jumped from 3-4% to 50-70% if you had three or more prior cesareans.  Clearly, multiple cesareans strongly increase the risk for placental issues in future pregnancies.

Many of these studies use risk ratios to compare the risk. This is useful in some ways, but mothers deserve to know what the exact numerical risk is for these conditions.  A 2006 large study was able to quantify this for women. In their study, they found that accreta was present in:

• 0.24% of women undergoing their first cesarean
• 0.31% of women having their second cesarean
• 0.57% of women having their third cesarean
• 2.13% of women having their fourth cesarean
• 2.33% of women having their fifth cesarean
• 6.74% of women having their sixth or more cesarean

In addition, they found that a hysterectomy was required in:

• 0.65% of  women having their first cesarean 
• 0.42% of women having their second cesarean 
• 0.90% of women having their third cesarean
• 2.41% of women having their fourth cesarean 
• 3.49% of women having their fifth cesarean
• 8.99% of women having their sixth or more cesarean

Obviously, the more cesareans you have, the more at-risk you are for complications. Complications like previa and accreta really start to rise after 3-4 or more cesareans.

However, sometimes these complications happen when a woman has "only" had one or two prior cesareans.  One study found that having a cesarean for the first birth raised the risk for placental abruption in the second pregnancy by 40% and for placenta previa by 47%.  So although the risks are greatest with 3 or more cesareans, poor outcomes can happen even after only one or two cesareans.  That's why it's important to prevent every cesarean that is not truly medically-indicated.

Even more important is to prevent the automatic repeat cesarean that happens to most women in this country (and in many countries around the world).  In many areas now, once a woman has a cesarean, she is not "allowed" to choose (or is pressured out of) having a subsequent vaginal birth.  And this is what leads to many cases of placental complications.

Most women will not experience severe complications despite undergoing multiple cesareans, but some WILL ─ like the woman who died recently while having her sixth cesarean. Now her children have to grow up without their mother.

This is why it is so important to prevent that first cesarean whenever possible, and why it is absolutely critical for women to have access to VBAC instead of being forced into cesarean after cesarean.



References

Increase in Incidence of Abnormal Placentation

Obstet Gynecol Clin North Am. 2013 Mar;40(1):137-54. doi: 10.1016/j.ogc.2012.12.002. Placenta accreta, increta, and percreta. Wortman AC, Alexander JM.  PMID: 23466142

Placenta accreta is an abnormal adherence of the placenta to the uterine wall that can lead to significant maternal morbidity and mortality. The incidence of placenta accreta has increased 13-fold since the early 1900s and directly correlates with the increasing cesarean delivery rate. The prenatal diagnosis of placenta accreta by ultrasound along with risk factors including placenta previa and prior cesarean delivery can aid in delivery planning and improved outcomes. Referral to a tertiary care center and the use of a multidisciplinary care team is recommended.

Risk Factors for Abnormal Placentation

Am J Obstet Gynecol. 2005 May;192(5):1458-61. Abnormal placentation: twenty-year analysis. Wu S, Kocherginsky M, Hibbard JU.  PMID: 15902137

OBJECTIVE: This study was undertaken to determine whether the rate of abnormal placentation is increasing in conjunction with the cesarean rate and to evaluate incidence, risk factors, and outcomes...RESULTS: There were 64,359 deliveries, with cesarean rates increasing from 12.5% (1982) to 23.5% (2002). The overall incidence of placenta accreta was 1 in 533. Significant risk factors for placenta accreta in our final analysis included advancing maternal age (odds ratio [OR] 1.13, 95% CI 1.089-1.194, P < .0001), 2 or more cesarean deliveries (OR 8.6, 95% CI 3.536-21.078, P < .0001), and previa (OR 51.4, 95% CI: 10.646-248.390, P < .0001). CONCLUSION: The rate of placenta accreta increased in conjunction with cesarean deliveries; the most important risk factors were previous cesarean delivery, previa, and advanced maternal age.

PLoS One. 2012;7(12):e52893. doi: 10.1371/journal.pone.0052893. Epub 2012 Dec 27. Incidence and risk factors for placenta accreta/increta/percreta in the UK: a national case-control study. Fitzpatrick KE, Sellers S, Spark P, Kurinczuk JJ, Brocklehurst P, Knight M. PMID: 23300807

...METHODS: A national case-control study using the UK Obstetric Surveillance System was undertaken, including 134 women diagnosed with placenta accreta/increta/percreta between May 2010 and April 2011 and 256 control women. RESULTS: The estimated incidence of placenta accreta/increta/percreta was 1.7 per 10,000 maternities overall; 577 per 10,000 in women with both a previous caesarean delivery and placenta praevia. Women who had a previous caesarean delivery (adjusted odds ratio (aOR) 14.41, 95%CI 5.63-36.85), other previous uterine surgery (aOR 3.40, 95%CI 1.30-8.91), an IVF pregnancy (aOR 32.13, 95%CI 2.03-509.23) and placenta praevia diagnosed antepartum (aOR 65.02, 95%CI 16.58-254.96) had raised odds of having placenta accreta/increta/percreta. There was also a raised odds of placenta accreta/increta/percreta associated with older maternal age in women without a previous caesarean delivery (aOR 1.30, 95%CI 1.13-1.50 for every one year increase in age). CONCLUSIONS: Women with both a prior caesarean delivery and placenta praevia have a high incidence of placenta accreta/increta/percreta. There is a need to maintain a high index of suspicion of abnormal placental invasion in such women and preparations for delivery should be made accordingly.

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

Placenta accreta is a rare and potentially life-threatening complication of pregnancy characterized by abnormal adherence of the placenta to the uterine wall. A previously scarred uterus or an abnormal site of placentation in the lower segment is a major risk factor. 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.

Placenta. 2012 Apr;33(4):244-51. doi: 10.1016/j.placenta.2011.11.010. Epub 2012 Jan 28. Placenta accreta: pathogenesis of a 20th century iatrogenic uterine disease. Jauniaux E, Jurkovic D. PMID: 22284667

Placenta accreta refers to different grades of abnormal placental attachment to the uterine wall, which are characterised by invasion of trophoblast into the myometrium. Placenta accreta has only been described and studied by pathologists for less than a century. The fact that the first detailed description of a placenta accreta happened within a couple of decades of major changes in the caesarean surgical techniques is highly suggestive of a direct relationship between prior uterine surgery and abnormal placenta adherence. Several concepts have been proposed to explain the abnormal placentation in placenta accreta including a primary defect of the trophoblast function, a secondary basalis defect due to a failure of normal decidualization and more recently an abnormal vascularisation and tissue oxygenation of the scar area. The vast majority of placenta accreta are found in women presenting with a previous history of caesarean section and a placenta praevia. Recent epidemiological studies have also found that the strongest risk factor for placenta praevia is a prior caesarean section suggesting that a failure of decidualization in the area of a previous uterine scar can have an impact on both implantation and placentation. Ultrasound studies of uterine caesarean section scar have shown that large and deep myometrial defects are often associated with absence of re-epithelialisation of the scar area. These findings support the concept of a primary deciduo-myometrium defect in placenta accreta, exposing the myometrium and its vasculature below the junctional zone to the migrating trophoblast. The loss of this normal plane of cleavage and the excessive vascular remodelling of the radial and arcuate arteries can explain the in-vivo findings and the clinical consequence of placenta accreta. Overall these data support the concept that abnormal decidualization and trophoblastic changes of the placental bed in placenta accreta are secondary to the uterine scar and thus entirely iatrogenic.

Placental Abruption and Prior Cesarean

Am J Perinatol. 2007 May;24(5):299-305. Epub 2007 May 18. Predicting placental abruption and previa in women with a previous cesarean delivery. Odibo AO, Cahill AG, Stamilio DM, Stevens EJ, Peipert JF, Macones GA. PMID: 17514600

The purpose of this study was to determine if placental abruption or previa in women with a history of a prior cesarean delivery (CD) can be predicted. A retrospective cohort study of pregnant women with previous CD was conducted in 17 centers between 1996 and 2000. Women developing placenta previa or abruption in the subsequent pregnancy were compared with those without these complications...Among 25,076 women with prior CD, there were 361 (15 per 1000 births) with placenta previa and 309 (13 per 1000 births) with abruption. The significant risk factors for these complications include advanced maternal age, Asian race, increased parity, illicit drug use, history of spontaneous abortion, and three or more prior cesarean deliveries. Prediction models for abruption and previa had poor sensitivity (12% and 13% for abruption and previa, respectively). In women with at least one prior cesarean delivery, the risk factors for placental previa and abruption can be identified. However, prediction models combining these risk factors were too inefficient to be useful.

Obstet Gynecol. 2006 Apr;107(4):771-8. Previous cesarean delivery and risks of placenta previa and placental abruption. Getahun D, Oyelese Y, Salihu HM, Ananth CV. PMID: 16582111

...METHODS: A retrospective cohort study of first 2 (n = 156,475) and first 3 (n = 31,102) consecutive singleton pregnancies using the 1989-1997 Missouri longitudinally linked data were performed. Relative risk (RR) was used to quantify the associations between cesarean delivery and risks of previa and abruption in subsequent pregnancies, after adjusting for several confounders. RESULTS: Rates of previa and abruption were 4.4 (n = 694) and 7.9 (n = 1,243) per 1,000 births, respectively. The pregnancy after a cesarean delivery was associated with increased risk of previa (0.63%) compared with a vaginal delivery (0.38%, RR 1.5, 95% confidence interval [CI] 1.3-1.8). Cesarean delivery in the first and second births conferred a two-fold increased risk of previa in the third pregnancy (RR 2.0, 95% CI 1.3-3.0) compared with first two vaginal deliveries. Women with a cesarean first birth were more likely to have an abruption in the second pregnancy (0.95%) compared with women who had a vaginal first birth (0.74%, RR 1.3, 95% CI 1.2-1.5). Two consecutive cesarean deliveries were associated with a 30% increased risk of abruption in the third pregnancy (RR 1.3, 95% CI 1.0-1.8). A second pregnancy within a year after a cesarean delivery was associated with increased risks of previa (RR 1.7, 95% CI 0.9-3.1) and abruption (RR 1.5, 95% CI 1.1-2.3). CONCLUSION: A cesarean first birth is associated with increased risks of previa and abruption in the second pregnancy. There is a dose-response pattern in the risk of previa, with increasing number of prior cesarean deliveries. A short interpregnancy interval is associated with increased risks of previa and abruption.

BJOG. 2007 May;114(5):609-13. Epub 2007 Mar 12. Association of caesarean delivery for first birth with placenta praevia and placental abruption in second pregnancy. Yang Q, Wen SW, Oppenheimer L, Chen XK, Black D, Gao J, Walker MC. PMID: 17355267

...SETTING: Linked birth and infant mortality database of the USA between 1995 and 2000. POPULATION: A total of 5,146,742 singleton second pregnancies were available for the final analysis after excluding missing information...RESULTS: Placenta praevia was recorded in 4.4 per 1000 second-birth singletons whose first births delivered by caesarean section and 2.7 per 1000 second-birth singletons whose first births delivered vaginally. About 6.8 per 1000 births were complicated with placental abruption in second-birth singletons whose first births delivered by caesarean section and 4.8 per 1000 birth in second-birth singletons whose first births delivered vaginally. The adjusted odds ratio (95% CIs) of previous caesarean section for placenta praevia in following second pregnancies was 1.47 (1.41, 1.52) after controlling for maternal age, race, education, marital status, maternal drinking and smoking during pregnancy, adequacy of prenatal care, and fetal gender. The corresponding figure for placental abruption was 1.40 (1.36, 1.45). CONCLUSION: Caesarean section for first live birth is associated with a 47% increased risk of placenta praevia and 40% increased risk of placental abruption in second pregnancy with a singleton.

Risks of Multiple Repeat Cesareans

Am J Obstet Gynecol. 2011 Dec;205(6 Suppl):S2-10. doi: 10.1016/j.ajog.2011.09.028. Epub 2011 Oct 6. Long-term maternal morbidity associated with repeat cesarean delivery. Clark EA, Silver RM. PMID: 22114995

Concern regarding the association between cesarean delivery and long-term maternal morbidity is growing as the rate of cesarean delivery continues to increase. Observational evidence suggests that the risk of morbidity increases with increasing number of cesarean deliveries. The dominant maternal risk in subsequent pregnancies is placenta accreta spectrum disorder and its associated complications. A history of multiple cesarean deliveries is the major risk factor for this condition. Pregnancies following cesarean delivery also have increased risk for other types of abnormal placentation, reduced fetal growth, preterm birth, and possibly stillbirth. Chronic maternal morbidities associated with cesarean delivery include pelvic pain and adhesions. Adverse reproductive effects may include decreased fertility and increased risk of spontaneous abortion and ectopic pregnancy. Clinicians and patients need to be aware of the long-term risks associated with cesarean delivery so that they can be considered when determining the method of delivery for first and subsequent births.

 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 JR, Jarvis S, Knight M, Dhanjal MK. PMID: 23095012

...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...RESULTS:...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.

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. 

Am J Obstet Gynecol. 2011 Sep;205(3):262.e1-8. doi: 10.1016/j.ajog.2011.06.035. Epub 2011 Jun 15. Impact of multiple cesarean deliveries on maternal morbidity: a systematic review. Marshall NE, Fu R, Guise JM. PMID: 22071057

...RESULTS: Twenty-one studies (2,282,922 deliveries) were included. The rate of hysterectomy, blood transfusions, adhesions, and surgical injury all increased with increasing number of cesarean deliveries. The incidence of placenta previa increased from 10/1000 deliveries with 1 previous cesarean delivery to 28/1000 with ≥3 cesarean deliveries. Compared with women with previa and no previous cesarean delivery, women with previa and ≥3 cesarean deliveries had a statistically significant increased risk of accreta (3.3-4% vs 50-67%), hysterectomy (0.7-4% vs 50-67%), and composite maternal morbidity (15% vs 83%; odds ratio, 33.6; 95% confidence interval, 14.6-77.4). CONCLUSION: Serious maternal morbidity progressively increased as the number of previous cesarean deliveries increased.

Obstet Gynecol. 2013 Apr;121(4):789-97. doi: 10.1097/AOG.0b013e3182878b43. Consequences of a primary elective cesarean delivery across the reproductive life. Miller ES, Hahn K, Grobman WA; Society for Maternal-Fetal Medicine Health Policy Committee. PMID: 23635679

OBJECTIVE: To estimate cumulative risks of morbidity associated with the choice of elective cesarean delivery for a first delivery. METHODS: A decision analytic model was designed to compare major adverse outcomes across a woman's reproductive life associated with the choice of elective cesarean delivery compared with a trial of labor at a first delivery. Maternal outcomes assessed included maternal transfusion, hysterectomy, thromboembolism, operative injury, and death. Neonatal outcomes assessed included cerebral palsy and permanent brachial plexus palsy in the offspring. RESULTS: Choosing an initial cesarean delivery resulted in a 0.3% increased risk of a major adverse maternal outcome in the first pregnancy. In each subsequent pregnancy, the difference in composite maternal morbidity increased such that by the fourth pregnancy, the cumulative risk of a major adverse maternal outcome was nearly 10% in the elective primary cesarean delivery group, three times higher than women who initially underwent a trial of labor. Although the choice of an initial cesarean delivery resulted in 2.4 and 0.41 fewer cases of cerebral palsy and brachial plexus palsy, respectively, per 10,000 women in the first pregnancy, by a fourth pregnancy, the risk of a adverse neonatal outcome was higher among offspring of women who had chosen the initial elective cesarean delivery (0.368% compared with 0.363%). CONCLUSION: Maternal morbidity associated with the choice of primary elective cesarean delivery increases in each subsequent pregnancy and is greater in magnitude than that associated with the choice of a trial of labor. These increased risks are not offset by a substantive reduction in the risk of neonatal morbidity.