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July, 2022

The diagnosis of placenta accreta spectrum (PAS) is difficult and sometimes uncertain. Despite years of research, PAS is still difficult to detect with ultrasound (or any other tests) in some cases. In the United States, up to 50% of patients with PAS are never diagnosed until the time of delivery. This can lead to in worse outcomes for patients who have PAS and deliver outside of a specialty center.

Outside of busy PAS specialty centers, the diagnosis may be missed. An important thing to remember is that PAS is relatively uncommon, and many ultrasound offices will rarely see this condition. Because of this, not every ultrasound you have during pregnancy is going to be focused on finding PAS, and not every ultrasound office will have the experience to make the diagnosis or determine the severity of PAS. One guideline in pregnancy care sums it up perfectly:

“Imaging is highly accurate when performed by a skilled operator with experience… [practioners should] refer women with any ultrasound features suggestive of PAS to a specialist unit with imaging expertise”

--Royal College of Obstetricians & Gynaecologists Green-top Guideline, 2018

What does it mean to get a second opinion? Second opinions involve having an expert outside of your doctor’s practice look over your specific medical situation and test results, then offer their diagnosis and recommendations for treatment. Sometimes it will confirm what you have already been told, and sometimes it may seem very different. It is not always necessary to change doctors after a second opinion, but some patients may want to. Sometimes the doctor providing the second opinion can work with your own doctor to make your delivery as safe as possible. 

Second opinions are recommended and common. PAS is not a routine pregnancy complication. Although people may be hesitant to seek a second opinion, you should know that this is common for complex conditions like PAS. For PAS care, second opinions are particularly important because this is such a difficult diagnosis to make, and the answers are not always clear. The leading organizations for pregnancy and women’s health recommend that patients with risk factors for accreta be referred to specialty centers with the most experience:

“It is advisable, whenever possible, to refer women with clinical risk factors for PAS to centers with experience and expertise in imaging and diagnosis of the condition”

--Joint American College of Obstetricians & Gynecologists/Society for Gynecologic Oncology/Society for Maternal-Fetal Medicine Statement, 2018


You might not be referred to a specialty center without seeking a second opinion. Studies from a few years ago suggest that only about 1 in 4 people with PAS will be referred by their OB provider to a specialty center for diagnosis and treatment. Thankfully, this is changing, and more patients are being referred. But far too many pregnant patients are either never referred for a second opinion or are referred late in pregnancy. So: how can you know if you need a second opinion for PAS care?  The following are suggestions to help you determine if you should get a second opinion.



Anybody with risk factors for PAS should consider an expert second opinion. The following types of patients are at highest risk:

  • People who have had a cesarean delivery before and have a low placenta. Low placentas can be called “low-lying” or “previa” on ultrasound reports. Low placentas that appear to have moved up over the course of pregnancy can still be PAS.

  • People who have any concerning ultrasound findings about the placenta. This may include “cannot rule out accreta,” “multiple lacunae,” “hypervascular changes,” “loss of clear space,” “bulging of the placenta” or “thinning myometrium.”

  • People who have had very difficult deliveries of the placenta in previous pregnancies. This may include “retained placenta,” “manual removal of the placenta,” “focal accreta,” or pathology reports with “basal plate myofibers.”


Does a second opinion or referral mean that I am switching hospitals or providers? Not necessarily. Depending on the situation, a second opinion or referral may be made to get help from an experienced PAS expert. Depending on your provider and hospital, and depending on the results of the second opinion, you may not need to transfer care or plan delivery at another hospital.


Should I have an MRI first, then go to the referral center? Probably not. MRI may not be necessary to make the diagnosis. Also, MRI is not generally helpful when it is performed outside of busy PAS specialty centers. Instead of getting an MRI, you should ask to meet with the PAS expert first. They may want to repeat your ultrasound. The expert can then determine whether to order MRI.




For people who have a diagnosis (or suspected diagnosis) of PAS, there may be benefits to seeking a second opinion. As accreta experts, we often seek additional opinions from other experts in the field. As a patient, it can be very difficult to know if you are getting care for PAS at the right hospital for your unique needs. 


Even with a sure diagnosis, PAS is unpredictable. No prenatal imaging or blood work can predict exactly how or when you will deliver or how difficult your delivery and surgery will be. Serious complications can occur even when the doctors think your case might be mild. Being prepared for the worst in every case is a hallmark of excellent PAS care. Whether your case is mild or severe, we advise people to have their PAS delivery and surgery at an experienced PAS specialty center.


There are a few important things to keep in mind for PAS care:

  1. Experience with PAS matters. Even great doctors and busy OB practices who can manage most pregnancy complications may not be sufficiently prepared for PAS. Patients who deliver at busy PAS specialty centers have safer deliveries than patients who deliver at hospitals where the doctors don’t see PAS very often. 

  2. The team matters more than the individual doctor or provider. The best PAS centers have dedicated teams of numerous doctors, nurses, and support staff devoted to caring for patients with PAS. The experience of the team is more important to patient safety than the individual experience of the doctor or surgeon.

  3. Planning is important. Safely preparing for PAS surgery takes a lot of time and discussion between teams (surgery, delivery, anesthesia, NICU, blood bank, and other services).

  4. Uncertainty is common. Many of the hardest PAS surgeries happen in patients who don’t have a clear diagnosis before delivery. Some patients go into surgery not knowing whether they will have a hysterectomy. This is common. The key is that the team is prepared for a hysterectomy if it is needed, and that the system is prepared for massive transfusion if heavy bleeding occurs.


So, if you have a possible diagnosis of PAS, consider a second expert opinion if:

  • your OB provider recommends a second or expert opinion, or

  • it is not evident that a lot of preparation is going into planning for your delivery and surgery, or

  • you are feeling uncertain about the level of care you are receiving, or

  • if you are not getting clear answers to your questions about PAS.


The best PAS centers are organized and transparent. At the current time, there is no formal accreditation process for PAS specialty centers, so it can be difficult for patients (and referring providers) to know where to seek a second opinion or expert care. To help determine if you are getting care at a hospital that is well equipped for PAS care, consider asking your practitioner the following questions:

  • Is my delivery hospital equipped to manage very heavy bleeding? Does it have more than enough blood for transfusion in the worst-case scenario?

  • Does my delivery hospital have all of the resources needed for PAS care?

  • How often (in a year) do you see PAS?

  • Are you open to referring patients for second opinions or team-based care?

  • Who are the other members of the accreta team? Can I meet them?

  • Can you tell me about your accreta protocol?



Great PAS teams work at Maternal Level of Care III (Subspecialty) or IV (Regional Perinatal Center) hospitals that can handle heavy bleeding and have dozens of units of blood to transfuse 24/7. They see many cases of PAS every year (more than 10), and may be willing to help local health care providers make decisions about your care. They are open to referring patients for second opinions, and often get other doctors asking them for second opinions. They are made up of multiple team members from all sorts of specialties including radiology, maternal-fetal medicine, anesthesiology, intensive care, blood bank, surgical specialties, and support services. They will often have a written accreta protocol, brochure, or website that explains their approach and they should be able to discuss the details with you.

Start by asking your own doctor if there are any specialty accreta programs in the area. You should feel able to talk to your doctor about your care options and second opinions. 

Alternatively, you can try calling the “high-risk” or “maternal fetal medicine” division of specialty hospitals in your state (or neighboring states, if needed). Ask if they have an accreta program or designated accreta specialist(s), or if they usual refer accreta patients to other practices. If they refer elsewhere, ask where that is.

In short, if asking these questions raises your concern that a lot of preparation isn’t going into your care for PAS, consider a second opinion from a PAS expert. 

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