Category Archives: Placental abnormalities


Thoughts on VBA3+C (VBAC after three or more prior cesareans)

Note regarding “TOLAC.”  When reading from medical texts, remember that you are no longer in the land of emotion and warm fuzzies.  Rather, envision that you have been transported to another world, a clinical world, where terms like TOLAC/TOLAMC, or trial of labor after (multiple) cesareans, are used.  I don’t think that most care providers understand the emotional sting that many women seeking VBAC associate with the term TOLAC.  It’s important for women to understand the language care providers use so that they can translate TOLAC into “planning a VBAC” and not feel slighted.  You might want to read this article which describes what the term TOLAC means, how it’s used in medical research, and why it’s not synonymous with VBAC.


A mom recently asked, “Does anyone have some facts on VBA3C?”

I provided this collection of info…

Who makes a good VBAC/VBAMC candidate?

ACOG’s 2010 VBAC recommendations affirm that VBA2C (vaginal birth after two cesareans) is reasonable in “some” women.  Between what they say about VBA2C and who is a good VBAC candidate, we might be able to discern who might be a good VBA3+C (vaginal birth after three or more cesareans) candidate. (For a really great, though growing outdated, review of the VBAMC research click here.)

A couple things to keep in mind while reading…

Reason for prior cesarean/history of vaginal birth.  Like women with one prior cesarean, I would suspect that women who have had cesareans for malpresentation (breech, transverse lie, etc) and/or a history of a prior vaginal delivery would have the highest success VBAMC (vaginal birth after multiple cesarean) rates.  In women with one prior cesarean, the average success rate is about 75%.  This increases to over 80% among women who had their cesarean for malpresentation and/or a history of a prior vaginal delivery.

Scar type.  Low transverse incisions (also called bikini cuts) carry the lowest risk of rupture in comparison to classical, high vertical and T/J incisions.  With the likely increased risk of uterine rupture in a VBAMC (we don’t have a lot of great data for VBA2C and even less so for VBA3+C), I think having low transverse incisions would be ideal.


Here ACOG describes the qualities of a good VBAC candidate:

Good candidates for planned TOLAC are those women in whom the balance of risks (low as possible) and chances of success (as high as possible) are acceptable to the patient and health care provider. The balance of risks and benefits appropriate for one patient may seem unacceptable for another. Because delivery decisions made during the first pregnancy after a cesarean delivery will likely affect plans in future pregnancies, decisions regarding TOLAC should ideally consider the possibility of future pregnancies.

Although there is no universally agreed on discriminatory point, evidence suggests that women with at least a 60–70% chance of VBAC have equal or less maternal morbidity when they undergo TOLAC than women undergoing elective repeat cesarean delivery (62, 63).  Conversely, women who have a lower than 60% probability of VBAC have a greater chance of morbidity than woman undergoing repeat cesarean delivery. Similarly, because neonatal morbidity is higher in the setting of a failed TOLAC than in VBAC, women with higher chances of achieving VBAC have lower risks of neonatal morbidity.  One study demonstrated that composite neonatal morbidity is similar between TOLAC and elective repeat cesarean delivery for the women with the greatest probability of achieving VBAC (63).

The preponderance of evidence suggests that most women with one previous cesarean delivery with a low transverse incision are candidates for and should be counseled about VBAC and offered TOLAC.  Conversely, those at high risk for complications (eg, those with previous classical or T-incision, prior uterine rupture, or extensive transfundal uterine surgery) and those in whom vaginal delivery is otherwise contraindicated are not generally candidates for planned TOLAC.  Individual circumstances must be considered in all cases, and if, for example, a patient who may not otherwise be a candidate for TOLAC presents in advanced labor, the patient and her health care providers may judge it best to proceed with TOLAC.

What does ACOG say about VBA2C?

In its latest VBAC recommendations, ACOG specifically addresses VBA2C:

Studies addressing the risks and benefits of TOLAC in women with more than one cesarean delivery have reported a risk of uterine rupture between 0.9% and 3.7%, but have not reached consistent conclusions regarding how this risk compares with women with only one prior uterine incision (64–68).  Two large studies, with sufficient size to control for confounding variables, reported on the risks for women with two previous cesarean deliveries undergoing TOLAC (66, 67).  One study found no increased risk of uterine rupture (0.9% versus 0.7%) in women with one versus multiple prior cesarean deliveries (66), whereas the other noted a risk of uterine rupture that increased from 0.9% to 1.8% in women with one versus two prior cesarean deliveries (67).  Both studies reported some increased risk in morbidity among women with more than one prior cesarean delivery, although the absolute magnitude of the difference in these risks was relatively small (eg, 2.1% versus 3.2% composite major morbidity in one study) (67).

Additionally, the chance of achieving VBAC appears to be similar for women with one or more than one cesarean delivery.  Given the overall data, it is reasonable to consider women with two previous low transverse cesarean deliveries to be candidates for TOLAC, and to counsel them based on the combination of other factors that affect their probability of achieving a successful VBAC.  Data regarding the risk for women undergoing TOLAC with more than two previous cesarean deliveries are limited (69).

The power of context and training

This hour long panel discussion followed the screening of More Business of Being Born: The VBAC Dilemma. On the panel are author/midwife Jenny West (The Complete Idiot’s Guide to Natural Childbirth and The Natural Healing Power of the Placenta), author/researcher Henci Goer (The Thinking Woman’s Guide to a Better Birth and Optimal Care in Childbirth), Nekole Shapiro of Embodied Birth, Stephanie Dawn of Sacred Birth and OB/GYN Dr. Craig Klose discussing the merits of vaginal birth after cesarean and various factors that may impede women being able to obtain VBACs.

One thing that stood out to me was Dr. Klose’s comments on VBAC after multiple prior low transverse cesareans (TLC). To sum, he says that he was taught that multiple LTCs were no biggie and he has attended up to VBA5C. This is the power of training and context!

ACOG guidelines, your legal rights, and “forced” cesareans

As attorney Lisa Pratt asserts, “ACOG guidelines are just that, guidelines, they are not law; while it is nice when they put out a guideline that supports your factual situation, falling outside of their recommendation does not mean you must consent to something you do not want.”  You can read in the article, “VBAC bans, exercising your rights, and when to contact an attorney.”

Further, ACOG also says that women cannot be forced to have cesareans even if there is a VBAC ban in place:

Respect for patient autonomy also argues that even if a center does not offer TOLAC, such a policy cannot be used to force women to have cesarean delivery or to deny care to women in labor who decline to have a repeat cesarean delivery.  When conflicts arise between patient wishes and health care provider or facility policy or both, careful explanation and, if appropriate, transfer of care to facilities supporting TOLAC should be used rather than coercion.  Because relocation after the onset of labor is generally not appropriate in patients with a prior uterine scar, who are thereby at risk for uterine rupture, transfer of care to facilitate TOLAC, as noted previously, is best effected during the course of antenatal care.  This timing places a responsibility on patients and health care providers to begin relevant conversations early in the course of prenatal care.

Read a summary of ACOG’s VBAC recommendations and the actual original document.  You may also wish to review your options when encountering a VBAC ban and the story of a mom seeking VBA2C who was threatened with a “forced” cesarean when her OB group withdrew support at 38 weeks.

Accreta, previa, hysterectomies, and cesareans

It has been well documented that the risks of placental abnormalities such as placenta accreta, placenta previa, and previa with accreta increase with each cesarean surgery and as a result, so does the rate of hysterectomy.  Silver (2006), a study of over 30,000 women and up to six cesareans quantified these risks per cesarean number.   You can read more about accreta, previa, previa with accreta and their associated complications.

Fang (2006) said, “abnormal adherent placentation [is] the primary indication leading to emergent peripartum [during the last month of pregnancy] hysterectomy… As the number of prior cesareans deliveries rises, the risk of cesarean hysterectomy increases dramatically.”

The Guise 2010 Evidence Report, which was the basis of the 2010 National Institutes of Health VBAC Conference, also discusses the risks of placental abnormalities by the number of prior cesareans.

So if you plan on having more children, a VBAMC (vaginal birth after multiple cesareans) would put a stop to the increasing rates of complications for future births as opposed to another cesarean which would just increase the risks in subsequent pregnancies.

Making a plan and moving forward

Your best bet is to review your medical records with several VBAC supportive care providers and get their opinion.  Obtain a copy of your medical records and operative reports from each prior cesarean, get the names of VBAC supportive providers, and ask the right questions.  Read more about planning a VBAC.

Woman has 4th cesarean and requires 33 gallons of blood

Update: This powerhouse of a woman has since started the non-profit organization “Hope for Accreta Foundation.”

What a miracle this woman survived!  This was her fifth baby and fourth cesarean.

She had a complication known as placenta percreta which is when “the placenta attaches itself and grows through the uterus, sometimes extending to nearby organs, such as the bladder” (March of Dimes 2012).  The risk of having placenta accreta, increta, or percreta during a fourth cesarean or a VBA3C (vaginal birth after three cesareans) is 2.13% (1 in 47) (Silver 2006).

Image credit: Wikipedia

Image credit: Wikipedia

Most women planning a VBA1C (vaginal birth after one cesarean) are aware of the risks of uterine rupture.  However, women planning their first vaginal birth or VBA1C need the WHOLE picture so they can really work to prevent an unnecessary cesarean.  They need to understand the risks and benefits of VBAC versus repeat cesarean for mom and baby now as well as how current choices impact mom’s future health, fertility, delivery options, and complications that present in subsequent births.

A huge part of this – I believe – is hiring a vaginal birth/VBAC supportive care provider because once a woman has that first cesarean, her options narrow, and they do so even more drastically after that second cesarean.  As her options narrow, her risks increase and unlike uterine rupture which you can circumvent through a repeat cesarean, the risk of accreta, percreta, and increta are not as easily mitigated.

By avoiding one complication, we are increasing our risk for another serious complication in future pregnancies.  For women who plan for large families, this should be on your radar and every practitioner should be discussing intended family size with their patients so that it can be taken into consideration.

Read more about placenta abnormalities, the risks of multiple cesarean sections, the marketing of risk, and how reversing VBAC bans would make birth safer for everyone.

And please donate blood. These women need it.

Woman survives crisis delivery with 33 gallons of donated blood

Posted on April 11, 2012 at 9:46 PM

SAN ANTONIO — University Hospital is sharing an incredible story of survival. A San Antonio woman was saved during a crisis baby delivery. But it took more than 33 gallons of blood.

Two-month-old Addison Walker came into the world in an unusual way. Her mother, Gina, had a rare pregnancy condition called placenta percreta. The placenta invaded through the uterine wall into the bladder, causing massive bleeding during a delivery operation.

Doctors at University Hospital recalled the February eight-hour operation.

“Unfortunately, Ms. Walker had blood loss that superseded anything that we could have prepared for,” said Dr. Jason Parker, U.T. Health Science Center OB/GYN.

Walker lost more than ten times the amount of blood surgeons anticipated. She needed more than 33 gallons. That’s 540 units to keep her alive.

“After I watched cooler after cooler after cooler with my wife’s name on it full of blood going up and down the hallways, yeah, I did get worried,” recalled Gina’s husband Dustin. Read more.

A couple comments left on Facebook:

University is a Level 1 trauma center.  It is the trauma center in San Antonio.  Only other hospital that takes the worst of the worst is SAMMC [San Antonio Military Medical Center] which is the military hospital.  University takes all the gunshots, stabbings, multiple injury accidents, etc…. And these come in multiple times a day.  If any hospital has 100+ units on hand it would be that hospital.  Even if it didn’t, it is literally a couple hundred yards from a half dozen other hospitals that could dip into their supply.

It’s approx $1060 per unit of blood from the blood bank, not including the one time cost of all the testing, which is about $400-500. (These costs depend on the facility, but are a ball park.) Think about what the cost of the blood alone was…

I laboured just fine with my attempted VBA3C but the labour pains at the end were intense and I needed some meds of sorts so I went off to the hospital only to be bullied into the surgery room. All stats were excellent with me and my baby (and noted by the doctors in surgery that my little girl was down the birth canal and had I only been given something to help with pain, I would have pushed her out just fine). Because of that unnecessarian I had to endure a 6 hour reconstructive surgery to fix the mistakes of all the other batched c-sections and to repair the fistula left by the 4th C. But in the meantime I got the pleasure of toting around a catheter for the 5 months in between surgeries. That’s on top of the other procedures, tests and pain I had to go through. All of this could have been avoided had the doctors not allowed me that very first c-section and all the others that were not required. I kick myself in the butt for not educating myself right from the beginning, but how was I to know the doctors wouldn’t be educated either!

I desire to go on to have more children, but am terrified for things like this article speaks of.

Placenta problems in VBAMC/ after multiple repeat cesareans

I thought that I would take the data from the Silver (2006) that I’ve previously discussed and share it in a different way that would be helpful to women with multiple prior cesareans.  (You might find it worthwhile to read this article specifically, where you can view the data below in graphs, as well as other articles on placental abnormalities first.)  Remember that accreta is when the placenta abnormality deeply attaches into the uterus requiring surgical removal.  There is a 7% maternal mortality rate with accreta as well as a high rate of hemorrhage and hysterectomy.   One of the factors that determines your risk of accreta or previa is your number of prior cesareans.

Whether a mom has a repeat cesarean or a VBA1C, her risk of accreta (including increta and percreta) and previa in that pregnancy are:

risk of accreta: 0.31% (1 in 323)
risk of previa: 1.3% (1 in 77)
risk of accreta if previa is present: 11% (1 in 9)

Whether a mom plans a third cesarean or a VBA2C, her risk of accreta and previa in that pregnancy are:<

risk of accreta: 0.57% (1 in 175)
risk of previa: 1.14% (1 in 88)
risk of accreta if previa is present: 40% (1 in 2.5)

If a mom plans a fourth cesarean or a VBA3C, the risk during that pregnancy increases to:

risk of accreta: 2.13% (1 in 47)
risk of previa: 2.27% (1 in 44)
risk of accreta if previa is present: 61% (1 in 1.6)

The jump in risk from two prior cesareans to three prior cesareans is pretty huge…

If mom plans a fifth cesarean or a VBA4C, the risk during that pregnancy increases to:

risk of accreta: 2.33% (1 in 43)
risk of previa: 2.3% (1 in 43)
risk of accreta if previa is present: 67% (1 in 1.5)

If mom plans a sixth cesarean or a VBA5c, the risk during that pregnancy increases to:

risk of accreta: 6.74% (1 in 15)
risk of previa: 3.4% (1 in 29)
risk of accreta if previa is present: 67% (1 in 1.5)

Here are some stats to consider:

Silver (2006) found the following rates of accreta (including increta and percreta), during the first, second, third, fourth, fifth, and sixth cesareans: 0.24%, 0.31%, 0.57%, 2.13%, 2.33%, 6.74%.  (View a graph of this data.)

In other words, your risk of placenta accreta increases from first to sixth cesarean delivery:
1 in 417,
1 in 323,
1 in 175,
1 in 47,
1 in 43,
1 in 15.

Read more about accreta.

The studies that have been conducted (that I’m aware of) on uterine rupture in VBAMC are kind of small (including hundreds, not thousands of women).  So I don’t think we have an accurate idea of VBA3C rupture risk.  This site is a great resource.

Update:  When I posted a link to this article on Facebook, a mom left this comment:

Thank you for posting. My friend had 2 previous c-sections, and with her 3rd pregnancy had the bad luck of having both placenta accreta and placenta previa (both risks of repeat c-section). Her pregnancy was awful..lots of bleeding, hospitalizations, steriods and other drugs to help hold onto the pregnancy and bedrest at 20 weeks. They couldn’t do cerclage because of the placenta previa). In the end she had a healthy baby, but a 5 hour c-section surgery where she lost a lot of blood and needed a blood transfusion of 6 units of blood. She had to have a hysterectomy and also they removed part of her bladder because her placenta had embedded so far it was attached to her bladder! She was pissed that her doctor never warned her of the risks of repeat c-sections. She is 39 years old.


yes, you can share my comment. again, my friend ultimately is ok bec she was planning on having her tubes tied after this 3rd unplanned pregnancy — but she was upset initially bec her OB never shared with her any of these risks of repeat c-section…and she said “had I known, I would have really pushed for a vbac with #2”

These are the complication rates that Silver 2006 found in 30,000
women during multiple cesareans.The rates quoted were what he found during the third CS but, I think
the accreta and previa rates illustrate the risks that are present
during a third pregnancy after two prior CS.In other words, whether a mom has a third CS or a VBA2C, her risk of
accreta and previa in that third pregnancy are:

risk of accreta: 0.57% (1 in 175)
risk of previa: 1.14% (1 in 88)
risk of accreta *if* previa is present: 40% (1 in 2.5)

If she has a third CS and becomes pregnant again, the risk during that
fourth pregnancy increases to:

risk of accreta: 2.13% (1 in 47)
risk of previa: 2.27% (1 in 44)
risk of accreta *if* previa is present: 61% (1 in 1.6)

Compare that to the risks in a first pregnancy:

risk of accreta: 0.24% (1 in 417)
risk of previa: 6.4% (1 in 16) [yes, that figure is correct, previa was the reason for many of these women’s primary CS]
risk of accreta *if* previa is present: 3% (1 in 33)

That means the risk of accreta increases 887% from the first pregnancy – a huge jump.

So, if it was me, getting that ultrasound and knowing I didn’t have these complications would give me huge peace of mind.

Just kicking the can of risk down the road

This is why cesareans should not be casual or performed for the convenience of anyone.  They should be reserved for real medical reasons so that the benefits of having the cesarean outweigh the risks.  And there are real risks to cesareans, but since the ones list below are future risks, they may seem less real.  Per a November 2011 study published in the Journal of Maternal-Fetal and Neonatal Medicine:

If primary and secondary cesarean rates continue to rise as they have in recent years, by 2020 the cesarean delivery rate will be 56.2%, and there will be an additional 6236 placenta previas, 4504 placenta accretas, and 130 maternal deaths annually. The rise in these complications will lag behind the rise in cesareans by approximately 6 years.

Placenta previa and accreta are nothing to mess around with.  Accreta in particular has a very high maternal mortality rate and many mothers end up having cesarean hysterectomies.   I write more about accreta here.

Many women do not think these complications are applicable to them as they don’t plan on more children after their two cesareans.  But I know many women, and I’m sure you do too, who were not planning on more children, but got pregnant nonetheless.  Unless you or your partner get sterilized or practice abstinence (what fun!), the chance of you getting pregnant is there.

By performing routine scheduled repeat cesareans, we do reduce the risk of uterine rupture in the current pregnancy, but we are also increasing the risks of accreta, previa, maternal death as well as uterine rupture in future pregnancies.  In addition, another large study found

[t]he risks of placenta accreta, cystotomy [surgical incision of the urinary bladder], bowel injury, ureteral [ureters are muscular ducts that propel urine from the kidneys to the urinary bladder] injury, and ileus [disruption of the normal propulsive gastrointestinal motor activity], the need for postoperative ventilation, intensive care unit admission, hysterectomy, and blood transfusion requiring 4 or more units, and the duration of operative time and hospital stay significantly increased with increasing number of cesarean deliveries.

And this is especially relevant in rural hospitals which institute VBAC bans because they don’t offer 24/7 anesthesia.  Even though the “immediately available” clause was removed in the latest (2010) ACOG VBAC Practice Bulletin, many of these bans still stand.

However, in order to rapidly respond to the potentially sudden diagnosis of accreta, previa, or abruption, the hospital will have to enact many of the same ideas provided at the 2010 NIH VBAC Conference on how a hospital without 24/7 anesthesia can safely offer VBAC and respond to uterine rupture.  So why not just institute those ideas from the get-go and offer VBAC to those who want it?  (I know, I know: medico-legal reasons, which the NIH also addressed, but that is another post.)  From VBAC Ban Rationale is Irrational:

 As David J. Birnbach, M.D., M.P.H (2010), who presented on the impact of anesthesiologists on the incidence of VBAC [at the 2010 NIH VBAC Conference] asserted:

Lack of immediate available of anesthesia may not always be a key factor in outcome [during a uterine rupture], especially in cases where the obstetrician is not present. Many cases of uterine rupture can be stabilized while the anesthesiologists becomes available, and examples have been suggested of ways to reduce the risk associated with such a crisis. These include antepartum [prenatal] consultation of VBAC patients with the anesthesia departments, development of cesarean delivery under local anesthesia protocols, finding methods of improving communication on labor and delivery suites, practice “fire-drills,” and development of protocols matching resources to risk.

I urge you to watch Dr. Birnbach’s presentation along with all the presentations from the 2010 NIH VBAC conference.

Read more about the how the risk of serious complications increase with each cesarean surgery.

Below is Silver’s (2006) study abstract:

J Matern Fetal Neonatal Med. 2011 Nov;24(11):1341-6. Epub 2011 Mar 7.

The effect of cesarean delivery rates on the future incidence of placenta previa, placenta accreta, and maternal mortality.

Solheim KN, Esakoff TF, Little SE, Cheng YW, Sparks TN, Caughey AB. Source Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, CA, USA. Abstract

OBJECTIVE: The overall annual incidence rate of caesarean delivery in the United States has been steadily rising since 1996, reaching 32.9% in 2009. Primary cesareans often lead to repeat cesareans, which may lead to placenta previa and placenta accreta. This study’s goal was to forecast the effect of rising primary and secondary cesarean rates on annual incidence of placenta previa, placenta accreta, and maternal mortality.

METHODS: A decision-analytic model was built using TreeAge Pro software to estimate the future annual incidence of placenta previa, placenta accreta, and maternal mortality using data on national birthing order trends and cesarean and vaginal birth after cesarean rates. Baseline assumptions were derived from the literature, including the likelihood of previa and accreta among women with multiple previous cesarean deliveries.

RESULTS: If primary and secondary cesarean rates continue to rise as they have in recent years, by 2020 the cesarean delivery rate will be 56.2%, and there will be an additional 6236 placenta previas, 4504 placenta accretas, and 130 maternal deaths annually. The rise in these complications will lag behind the rise in cesareans by approximately 6 years.

CONCLUSIONS: If cesarean rates continue to increase, the annual incidence of placenta previa, placenta accreta, and maternal death will also rise substantially.

Shows the rates of placenta accreta in up to six cesareans (Silver 2006).

Risk of serious complications increase with each cesarean surgery

Yesterday I shared a Canadian article, and last year a letter from two OBs opposing a hospital VBAC ban, which discuss the risks of cesarean sections including placenta accreta and hysterectomy.


Today I want to share a study that measured the increasing risks that come with multiple cesareans, but before I do so, lets do a quick review of definitions.

Placenta accreta (March of Dimes 2005):

In a normal pregnancy, the placenta attaches itself to the uterine wall, away from the cervix.

  • Placenta accreta is a placenta that attaches itself too deeply and too firmly into the wall of the uterus.
  • Placenta increta is a placenta that attaches itself even more deeply into the uterine wall.
  • Placenta percreta is a placenta that attaches itself through the uterus, sometimes extending to nearby organs, such as the bladder.

Hysterectomy (Women’s Health 2009):

A hysterectomy (his-tur-EK-tuh-mee) is a surgery to remove a woman’s uterus or womb. The uterus is where a baby grows when a woman is pregnant. The whole uterus or just part of it may be removed. After a hysterectomy, you no longer have menstrual periods and cannot become pregnant.

Placenta previa (PubMedHealth 2011):

Placenta previa is a complication of pregnancy in which the placenta grows in the lowest part of the womb (uterus) and covers all or part of the opening to the cervix.

There are different forms of placenta previa:

  • Marginal: The placenta is next to cervix but does not cover the opening.
  • Partial: The placenta covers part of the cervical opening.
  • Complete: The placenta covers all of the cervical opening.

Increasing risks with multiple cesareans: Focusing on accreta

Today’s study is Maternal morbidity associated with multiple repeat cesarean deliveries (Silver 2006) which included over 30,000 women undergoing up to six cesareans over four years.  (Download the full text PDF.)  Silver measured the complication rates per cesarean number.  And their findings are important to every mom pregnant after a cesarean.  Keep in mind that all the cesareans included in the Silver (2006) study were schedule and performed without medical indication except for the first cesarean.  All the complications noted were a direct result of the surgery, not of any other medical complication.

Silver (2006) found:

The risks of placenta accreta, cystotomy [surgical incision of the urinary bladder], bowel injury, ureteral [ureters are muscular ducts that propel urine from the kidneys to the urinary bladder] injury, and ileus [disruption of the normal propulsive gastrointestinal motor activity], the need for postoperative ventilation, intensive care unit admission, hysterectomy, and blood transfusion requiring 4 or more units, and the duration of operative time and hospital stay significantly increased with increasing number of cesarean deliveries.

Accreta was defined as the “placenta being adherent to the uterine wall without easy separation [and] included placenta accreta, increta, and percreta.”

Below are some slides from the VBAC Class I developed and teach illustrating the  rates of placenta accreta, previa, previa with accreta, and hysterectomy by number of cesareans (Silver 2006).   The number below the cesarean number indicate how many women were included in that category.

Remember as you look these over, the risk of uterine rupture in a spontaneous labor after one prior low horizontal (“bikini-cut”) cesarean is 0.4% (Landon 2004).  Risk of uterine rupture during one’s second cesarean is 0.9% (Landon 2006).

Shows the rates of placenta accreta in up to six cesareans (Silver 2006).

 Shows the rate of placenta previa by cesarean number (Silver 2006).

Accreta, previa, and cesarean hysterectomies

I was especially interested to see the relationship between previa and accreta.  Silver (2006) found that if you have previa, you are very likely to have accreta and that risk increases with each cesarean.  For example, if a woman has one cesarean and is diagnosed with previa in her next pregnancy, her risk of having accreta is 11%.  That risk jumps to 40% in the third pregnancy, 61% in the fourth pregnancy and 67% for the fifth and sixth pregnancy.

Shows the rate of placenta previa with accreta per Silver 2006.

Complications associated with accreta

Accreta is nothing to mess around with as it has a very high rate of maternal mortality (up to 7%) and morbidity including hemorrhage and hysterectomy.  Fang (2006) asserted, “abnormal adherent placentation [is] the primary indication leading to emergent peripartum hysterectomy…. As the number of prior cesarean deliveries rises, the risk of cesarean hysterectomy increases dramatically.”   In other words, all these primary cesareans and repeat cesareans are causing placentas to abnormally implant in subsequent pregnancies.  As a result, many women who have placenta accreta end up having hysterectomies as that is the best way to control the hemorrhaging that results from accreta.

Rate of hysterectomy by cesarean number (Silver 2006).

Women who had accreta also experienced the following complications:

  • 15.4% (1 in 6.5): surgical injury to bladder
  • 2.1%  (1 in 48): surgical injury to the ureters which are the tubes that connect the kidneys to the bladder and is the “most serious complication of gynecologic surgery
  • 2.1%  (1 in 48 ): blockage of an artery in the lungs (pulmonary embolism)
  • 14% (1 in 7):  mom was put on a mechanical ventilator because she couldn’t breathe effectively
  • 26.6% (1 in 3.8): mom requires advanced monitoring and care so she is admitted to the intensive care unit
  • 5.6% (1 in 17.8): mom requires another operation
  • 3.5% (1 in 28.6): endometritis, “an inflammation or irritation of the lining of the uterus”

Because the risks of cesarean are so great, Silver (2006) concluded with the following statement,

Because serious maternal morbidity increases progressively with increasing number of cesarean deliveries, the number of intended pregnancies should be considered during counseling regarding elective repeat cesarean operation versus a trial of labor and when debating the merits of elective primary cesarean delivery.

Alternatives to cesarean hysterectomy

Non-hysterectomy options were discussed in a February 2006 Healthline article by Alison Stuebe, Department of Maternal-Fetal Medicine, Brigham and Women’s Hospital, Boston, MA:

In the majority of cases, hysterectomy is the most effective way to manage the potentially fatal consequences of placenta accreta. Unfortunately, however, most cases of placenta accreta are not discovered until the last minute. And, because a hysterectomy results in infertility, some women may want to consider more conservative options.

Conservative or alternate techniques for treating placenta accreta include:

  • curettage (scraping) of the uterus;
  • surgical repair of the part of the uterus where the placenta was attached;
  • clamping the blood vessels that nourish the pelvis (to control the bleeding); and
  • using x-ray guidance to inject gelatin sponge particles or spring coils into the blood vessels that nourish the uterus (this procedure usually is not feasible in emergency situations.) This procedure requires help from interventional radiologists, doctors who specialize in advanced treatments for bleeding.

Reported success rates of these procedures vary widely. In one recent study, 31 cases of placenta accreta were managed without hysterectomy; there were no reports of infertility or maternal death.

Using ultrasound and MRI to diagnose accreta

All the statistics I have shared above are from hospital based studies where women have access to operating rooms, surgeons, and blood products.  I suspect that the likelihood of a mother dying from hemorrhage due to placenta accreta is significantly higher in an OOH (out-of-hospital) birth.  This is why I think it is completely reasonable to have an ultrasound or MRI to try to diagnose accreta when planning a OOH birth.

Although second and third trimester bleeding can be a symptom for previa, I was surprised to read on the University of Maryland Medical Center’s website, “About 7% to 30% of women with placenta previa do not experience vaginal bleeding as a symptom before delivery.”   Thus one cannot rely on bleeding during pregnancy as a reliable symptom for previa which is why ruling it out via ultrasound appears to be a effective plan. (No citation was given, so if anyone has information to affirm or refute this stat, please leave a comment.)

There appears to be some controversy about the ability to accurately diagnose accreta during pregnancy.  According to a 2011 Medscape article byDr. Robert Resnik, “the diagnosis [of placenta accreta] can be made with accuracy, by very specific ultrasound findings, about 80% of the time, and can be confirmed with MRI findings.”

However, in a 2010 article published in the Journal Watch Women’s Health, Andrew M. Kaunitz, MD states, “If ultrasound findings [while looking for accreta] are not definitive, MRI evaluation is appropriate.  Unfortunately, the diagnostic precision of these two imaging modalities for placenta accreta can be suboptimal.”

I also highly recommend you read Dwyer (2008) which provides an excellent overview and compared the accuracy of the two methods:

Sonography correctly identified the presence of placenta accreta in 14 of 15 patients (93% sensitivity) and the absence of placenta accreta in 12 of 17 patients (71% specificity). Magnetic resonance imaging correctly identified the presence of placenta accreta in 12 of 15 patients (80% sensitivity) and the absence of placenta accreta in 11 of 17 patients (65% specificity). In 7 of 32 cases, sonography and MRI had discordant diagnoses: sonography was correct in 5 cases, and MRI was correct in 2.

Because of this high rate of maternal mortality and morbidity, some doctors suggest if accreta is diagnosed via ultrasound and/or magnetic resonance imaging (MRI) during pregnancy, a cesarean hysterectomy should to performed as early as 34 – 35 weeks.  (Read Does Antenatal Diagnosis of Placenta Accreta Improve Maternal Outcomes?, The maternal outcome in placenta accreta: the significance of antenatal diagnosis and non-separation of placenta at delivery and Placenta accreta: A dreaded and increasing complication for more information on early delivery via cesarean section.)

What difference does it make if you know you have accreta before delivery?

Because accreta has a high maternal mortality and morbidity rate, a hospital plans for a birth with accreta (usually a cesarean if diagnosed before labor) very differently than a birth (cesarean or vaginal) without known accreta.

One night during my endless random reading, I stumbled across the Royal College of Obstetricians and Gynaecologists’ (the UK’s ACOG) clinical guidelines for placenta praevia, placenta praevia accreta and vasa praevia.  (Note that the Brits do spell previa/praevia differently than Americans.)  This document included a detailed description of how they recommend a hospital plan for a cesarean birth due to placenta accreta:

The six elements considered to be reflective of good care were:
1. consultant obstetrician planned and directly supervising delivery
2. consultant anaesthetist planned and directly supervising anaesthetic at delivery
3. blood and blood products available
4. multidisciplinary involvement in pre-op planning
5. discussion and consent includes possible interventions (such as hysterectomy, leaving the placenta in place, cell salvage and intervention radiology)
6. local availability of a level 2 critical care bed.

Taking this extensive preparation into account, I suspect that women fare better when accreta is diagnosed before delivery.

Evidence to suggest previa less likely to “move” in VBAC/VBAMC moms

RCOG’s clinical guidelines also included evidence that of women who were diagnosed with previa early in their pregnancy, women with a prior cesarean where less likely than an unscarred mom to have their placenta “move” enough to permit a vaginal delivery at term (50% vs. 11%).  Since the study in question included over 700 women with previa, this is a large enough study to give us good evidence.

Women with a previous caesarean section require a higher index of suspicion as there are two problems to exclude: placenta praevia and placenta accreta.  If the placenta lies anteriorly and reaches the cervical os at 20 weeks, a follow-up scan can help identify if it is implanted into the caesarean section scar.

Placental ‘apparent’ migration, owing to the development of the lower uterine segment, occurs during the second and third trimesters,52–54 but is less likely to occur if the placenta is posterior55 or if there has been a previous caesarean section.35  In one study, only five of 55 women with a placenta reaching or overlapping the cervical os at 18–23 weeks of gestation (diagnosed by TVS) had placenta praevia at birth and in all cases the edge of the placenta had overlapped 15 mm over the os at 20 weeks of gestation.56  A previous caesarean section influences this: a large retrospective review of 714 women with placenta praevia found that even with a partial ‘praevia’ at 20–23 weeks (i.e. the edge of the placenta reached the internal cervical os), the chance of persistence of the placenta praevia requiring abdominal delivery was 50% in women with a previous caesarean section compared with 11% in those with no uterine scar.53

Conversely, although significant migration to allow vaginal delivery is unlikely if the placenta substantially overlaps the internal os (by over 23 mm at 11–14 weeks of gestation in one study,54 by over 25 mm at 20–23 weeks of gestation in another52 and by over 20 mm at 26 weeks of gestation in a third study57), such migration is still possible and therefore follow-up scanning should be arranged.

I looked up source 53 and it’s Dashe (2002) which shared:  “The outcome of the study was persistent placenta previa resulting in cesarean delivery.  This diagnosis was based on clinical assessment and ultrasound at time of delivery.”  You can read Dashe in its entirety by clicking on this link and then looking for the “Article as PDF” link on the right hand side.

Considering your future fertility

Many women who don’t plan on having more children do not think these complications are applicable.  But I know many women, and I’m sure you do too, who were not planning on more children, but got pregnant nonetheless.  This is consistent with the CDC’s findings that 49% of pregnancies are unintentional.  Unless you or your partner get sterilized or practice abstinence (what fun!), the chance of you getting pregnant, and experiencing these downstream risks, are there.  It’s important when evaluating your current birth options to consider how that decision will impact the risks of your future pregnancies as well as your future delivery options.

Last updated 9/13/12.