Symptoms

Three of the included patients presented with painless vaginal bleeding during pregnancy, lasting 3.7 ± 3.1 days; In 6 cases, abnormal placenta position was found, and no symptoms such as vaginal bleeding and abdominal pain were found. Placenta accreta was diagnosed during cesarean section in 9 cases. 5 cases showed residual placenta and continuous vaginal bleeding after abortion. Another 2 cases showed placental retention after delivery, with little vaginal bleeding, and 1 of them was preterm delivery. The signs and clinical manifestations of most patients were not obvious, but patients with placenta previa often complicated with painless vaginal bleeding.

Auxiliary examination

All patients underwent ultrasound examination after admission, 7 cases showed unclear boundary between uterine muscle wall and placenta; one case suggested that the uterine base was thin; one case suggested placental thickening. In all eight cases of placenta previa, five ultrasound showed low or varying degrees of placenta covering the cervix. In addition to the location of placenta and the judgment of the relationship between placenta and uterus, ultrasound can also accurately measure the thickness of uterine muscle layer and the richness of blood flow signals. Pelvic Magnetic Resonance Imaging (MRI) was performed in two patients, suggesting that irregular mixed signal shadows were seen in the uterine cavity, and the myometrium was implanted in different degrees. For patients with postpartum placental residue, serum Human Chorionic Gonadotropin (HCG) has a reference effect on the treatment effect.

Treatment and outcomes

Four patients had massive bleeding in cesarean section at the lower uterine segment, and finally subtotal hysterectomy. Among them, 2 cases were given arterial embolization in advance to reduce bleeding. Case 5: Intrauterine balloon tamponade was performed after cesarean section, but the balloon fell off spontaneously two hours after operation, and a large amount of vaginal bleeding was accompanied by old blood clots. Finally, subtotal hysterectomy was performed. In cases 1, 3, 6, 8, 9, 10 and 14, partial placenta accreta was localized by ultrasound before operation, and partial hysterectomy (Triple P procedure) was performed after blocking uterine blood supply. All patients had different degrees of uterine wall FFP membrane surface vascular anger, muscle layer thickness decreased. Placenta and uterine wall adhesion is closely, uterine wall depression can be seen when pulling the placenta. Three patients underwent curettage after arterial embolization, and case 12 underwent hysteroscopic removal of pregnancy residues.

A total of 10 patients with postpartum hemorrhage were treated with blood transfusion, including 5 cases of hemorrhagic shock. Case 4,6 and case 11 underwent MTX + calcium folinate intramuscular injection after curettage under ultrasound guidance, and the blood HCG decreased ideally. In case 13, the placenta was kept in situ, and the placenta absorption was monitored by ultrasound every month. Two months after delivery, the echo of placenta was reduced to 12 x 6 x 8 mm, and the blood HCG decreased ideally, which was still in follow-up. In addition to induced labor cases, the prognosis of all full-term newborns was good, and the prognosis of newborns in Case 1 and Case 8 was good after being rescued in neonatal department due to premature birth (Table 2).

Discussion

Forepassed uterine surgery is one of major risk factors for placenta accreta

The character of normal early human placental development is to implant blastocyst into the decidualized endometrium. The decidualized bottom deciduum is a strip of detachment that separates the placenta from the myometrium, allowing the placenta to be expelled during the third stage of labor. Due to all kinds of previous uterine surgery, defects in the decidua at the implantation site can cause placental tissue to contact with the myometrium directly, preventing the normal strip to form, leading to unsuccess of placental detachment during delivery [13]. Most of the cases in this medical record analysis had a history of more than two uterine surgeries, and the short time from the previous uterine surgery also increased the depth of placenta accreta. Due to the increasing of uterine surgeries and the insufficient time since the last uterine surgery, the endometrium cannot regenerate the strong decidua layer at the scar site. Placenta previa is commonly found at the lower segment of the uterus muscle layer which is relatively thin, placental tissue is easy to penetrate muscle layer and even invades the bladder and other important organs. In addition, maternal high collar increases the probability of cesarean section and placenta previa.

Ultrasound has specificity in prenatal diagnosis of placenta accreta and MRI can be regarded as a supplement

The results of a meta-analysis indicated that in 3707 pregnancies, the specificity and sensitivity of ultrasound in the diagnosis of PAS were about 90.72% and 96.94%, among which the accuracy of color Doppler ultrasound was the highest, with sensitivity and specificity reaching 90.74% and 87.68% [14]. MRI is another method used for prenatal diagnosis of PAS. A meta-analysis showed that the overall specificity of MRI for PAS was 84.0%, and the sensitivity was 94.4% [15].

A prospective study of 1256 women at high risk, such as prior uterine surgery and placenta previa, showed that ultrasound at 12 to 16 weeks was highly predictive for the occurence of placenta accreta during the third trimester of pregnancy, with only one false positive result for all 13 cases in the detected population that suggested placenta accrete [16]. In the study, ultrasound examination could show the placenta position. Among the 8 patients with intraoperative placenta previa, ultrasound indicated that the placenta covered the internal cervix or was in a low position in 6 cases. In all cases of placenta percreta, ultrasound examination showed that the boundary between placenta tissue and muscularis uteri was not clear, and some of them showed too thin muscularis uteri and abundant blood flow signals.

In cases 9, 15 and 16, MRI was more accurate in distinguishing the degree and area of placenta accreta. MRI may be more accurate when placenta accreta is suspected, particularly when the placenta may extend into the bladder, rectum, cervix, or parametrial tissues or when the placenta is found in the posterior and bottom wall of uterus [17].

Different treatment plans should be adopted for different implantation areas and depths

Pathologists have classified it into three subtypes: (1) superficial placenta accreta: The villi is directly attached to the surface of myometrium, but without invading the myometrium; (2) Placenta increta: The villi penetrating into the myometrium of uterus and extending to the outer layer; (3) Placenta percreta: In which invasive villous tissue reaches and penetrates the uterine myometrium and serosa [18].

Placental adhesion or shallow implantation

According to the experience of our hospital, for patients with shallow placental implantation without penetrating the myometrium, uterine artery embolization can temporarily block the uterine blood supply and reduce the total amount of blood loss. Intraarterial injection of low dose MTX during embolization can make it act locally on the uterus and placenta, effectively promoting the necrotic absorption of residual placenta tissue. After surgery, the placental blood supply at the implantation site was evaluated by Doppler color doppler ultrasound, and uterine clearance was performed under ultrasound guidance or hysteroscopy when there was no obvious blood flow signal. In cases 12, atrophy of placental tissue was observed under hysteroscopy, and resistance and blood loss were significantly reduced during uterine clearance.

Placenta percreta

PAS is the main cause of peripartum hysterectomy, with up to 64% of PAS patients undergoing hysterectomy [19,20]. And 40%-50% of the patients will still have serious postoperative complications, and 7% of the early maternal death [21]. Triple P procedure is a new uterus preserving surgical technique, which includes three steps: Partial location of placenta accreta before ultrasound or MRI examination before surgery; Selective internal iliac artery embolization or use of pelvic artery occlusion balloon catheter to lower blood supply to the placenta; The implanted placenta and its attached myometrium were removed without separation and the uterus was further repaired. It was first proposed in 2004 and has recently been widely referred to as Triple P procedure [22]. Conservative treatment can significantly reduce the amount of bleeding in patients with a small implantation area, while resection (removal of all the uteroplacental implantation and closure of the gap) can reduce the amount of bleeding and preserve fertility in patients with a large implantation area that is difficult to repair [23].

Due to abundant angiogenesis at the implantation site, uterine artery embolization can not always effectively block uterine blood supply, and uterine clearing is also easy to cause uterine perforation, massive bleeding and other complications. When it was found that placenta was only implanted locally and most placentas developed normally, Triple P procedure removed placenta tissue as much as possible without attempting to separate placenta and muscle, which greatly reduced intraoperative bleeding and other potential risks during placenta absorption as much as possible, so as to preserve female reproductive function. Cases 1, 3, 6, 8, 9, 10 and case 14 all had good prognosis after Triple P procedure.

According to the treatment experience of our hospital, in patients with large-area placental penetration implantation, blood vessels in the old scar of the lower uterine position are common in operation, and the placental tissue penetrates from the uterine muscle layer, which is difficult to forcibly peel and prone to massive bleeding, and due to the thin uterine base, accompanied by uterine weakness. When the penetrating implantation area is too large (>10 × 10 cm²), local resection of the placenta and its attached myometrium will result in a large area of myometrium loss, and it is difficult to restore the normal anatomical structure of the uterus. Due to the excessive wound area, the risk of causing bleeding and infection is increased, hysterectomy is performed in some cases. Hysterectomy is a traditional practice, either as an selective or emergency plan for massive bleeding. But the downside is a higher damage rate for neighbouring organs such as the ureter or bladder, and the inevitable permanent loss of fertility.

Placenta retention in situ may be risky

Expectant management refers to the preservation of part or all of the placenta in situ. A study of 167 cases showed that 78% (131/167) of PAS patients did not require hysterectomy after expectant management, and the average time of placenta expulsion in successful expectant management patients was 13.5 weeks. However, 22% (36/167) of PAS patients still needed hysterectomy due to severe complications (bleeding, severe infection) during the expectant treatment [24]. Other studies have found similar findings [25].

After fetus delivered, the umbilical cord should be ligated as close to the placenta as possible without attempting to isolate the placenta from the uterine wall. There is an advantage of placenta in situ which is minimizing the possibility of intraoperative bleeding. Case 15 in this study had postpartum placenta retention and was generally in good condition upon admission. The placenta was planned to be retained in situ and treated with anti-inflammatory hemostatic therapy. On the third day of conservative treatment, a large amount of vaginal bleeding occurred, accompanied by infection symptoms such as elevated body temperature and abnormal verification indicators. Finally, total hysterectomy was performed. Case 16, blood HCG on admission: 1075 mIU/mL, blood HCG decreased less than ideal within 2 weeks after placenta retention in situ, and MTX treatment was finally performed.

Placental retention in situ requires a long period of regular ultrasound and follow-up to determine HCG to ensure the placental tissue reabsorbed completely, which could require good patient compliance. Due to progressive necrosis, it takes more than 4 months for the placental tissue to fully absorb, during which time there is a high stake of sepsis and secondary bleeding. According to our hospital’s experience, the in situ placental retention scheme is only suitable for cases with placental adhesion area less than 3 × 3 cm and blood HCG less than 200 mIU/mL.

Conclusion

The number of PAS cases has increased exponentially in the last couple of years, and this data seems to increase further in the years ahead due to the increase of assisted reproductive technology and caesarean section. As the incidence increases, so does the clinician’s experience, the crux to improving infant and maternal outcomes is prenatal diagnosis. Ultrasound is as accurate as MRI in diagnosing PAS, especially when the placenta invading the uterine wall and in a low segment. The increase in placenta accreta has also created the requirements of innovation in surgical techniques that are more conservative, and reduce the happening of psychological and physical effects of hysterectomy. Of these, Triple P procedure has proven a good prognosis, with a low rate of postpartum bleeding, allowing women who wish to conceive again to remain fertile after a period of contraception.

Besides the surgical technique chosen, women with higher degree of suspicion or confirmation of PAS should be treated by a multidisciplinary team at a medical facility with surgical expertise. The team should have complex case management experience, blood products, interventions, Neonatal Intensive Care Units (NICU) and Intensive Care Units (ICU) are all necessary. Termination of pregnancy at 35 to 37 weeks is recommended to attain the optimum balance between the risk of preterm birth and natural birth.

Declarations

Patient consent statement: All Patients were tested for their immediate recall and medical history of information presented recorded, and signed on informed consent documents.

Funding statement: The authors have no sources of funding to declare.

Disclosure of interest: The authors report no conflict of interest.

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