Overview

Placenta accreta is a serious pregnancy condition in which the placenta grows too deeply into the walls of the uterus, making it difficult to detach after childbirth. The extent of invasion varies, which is why placenta accreta is considered a spectrum of diseases, known as the placenta accreta spectrum (PAS). It is also referred to as the abnormal invasion of placenta (AIP). It is generally considered to be iatrogenic, meaning it is caused by medical procedures. Surgeries that involve the uterus, especially prior caesarean section deliveries, are the most common risk factors for the development of PAS. Severe haemorrhage during delivery and damage to surrounding organs during the surgical removal of the placenta are some of the most common and critical complications of PAS. Consequently, PAS can have serious implications on a woman’s fertility, both as a direct cause of the condition itself and as a consequence of its management. 

Background on placenta accreta

In a normal pregnancy, the placenta attaches to the most superficial layer of the uterus, leaving the deeper, muscular layer of the uterus unaffected. This is important as the shallow attachment allows the placenta to detach easily after childbirth. Placenta accreta occurs when the placenta attaches abnormally, too deeply, into the uterine walls. Based on the depth of invasion of the placenta into the uterine wall, this condition is a spectrum of disorders known as placenta accreta spectrum (PAS).¹

The three conditions that fall under PAS are as follows:

• Placenta accreta - The placenta attaches too deeply into the uterine wall, but does not invade the muscles of the uterus
• Placenta increta - The placenta invades the muscular layer of the walls of the uterus
• Placenta percreta - The placenta penetrates through the entirety of the muscular walls of the uterus, and may even attach to nearby organs, such as the bladder

Risk Factors 

Although the exact cause and mechanism of the development of placenta accreta is not fully understood, it is believed that damage in the superficial layer of the walls of the uterus, the decidua basalis, leads to the abnormal invasion of placental cells, known as trophoblasts, into the defective area.² 

The damage to the walls of the uterus are usually caused by uterine surgical procedures. The most common risk factors of PAS are as follows:³

• Previous caesarean deliveries - Risk of placenta accreta increases with the number of prior caesarean deliveries.⁴
• Placenta previa - Placenta previa is a condition where the placenta partially covers the cervix. In normal pregnancies, the placenta attaches to the top part of the uterus, known as the fundus, that is across the cervix.
• Advanced maternal age
• Prior uterine surgeries or curettage
• Assisted reproductive technology (ART)-related pregnancies⁵
• Smoking during pregnancy
• Uterine anomalies 

Diagnosis

Antenatal (before birth) diagnosis of placenta accreta is done using ultrasound. Most women are diagnosed in their second or third trimester, but ultrasonographic features of placenta accreta can be detected as early as the first trimester. Women who are at risk of developing placenta accreta, like those who have a history of uterine surgery or a prior diagnosis of placenta previa, are encouraged to undergo evaluation. Another method of diagnosing PAS is colour flow doppler imaging, which detects turbulent blood flow within the placenta and other findings indicative of placenta accreta.  

Magnetic resonance imaging (MRI) may be utilised to assess the depth of invasion in suspected placenta percreta. MRI may be useful in difficult cases such as posterior placenta previa, where the position of the placenta makes detection via ultrasound difficult.³

Those diagnosed with placenta accreta spectrum should be referred to centres with considerable experience in managing such conditions. Early diagnosis is crucial as it allows the multidisciplinary teams within the hospitals and the community to plan pregnancy care and delivery accordingly. 

Management

The prenatal steps in the management of PAS are early diagnosis, taking a multidisciplinary approach, and planning the delivery. Caesarean delivery is typically scheduled around weeks 34-35 of pregnancy to prevent labour complications. 

Intrapartum management includes having massive blood product transfusion protocols in place to manage potential haemorrhage.⁶ Due to the deep attachment of the placenta in PAS, its detachment at birth often leads to massive bleeding that needs to be managed surgically. Manual removal of the placenta, also known as the extirpative method, is avoided to prevent severe haemorrhage.⁷

However, in severe cases, a caesarean hysterectomy, a procedure where the uterus itself is removed during caesarean section delivery, is planned. Caesarean hysterectomy is a technically challenging surgical procedure with a high risk of haemorrhage, necessitating the presence of experienced gynaecological surgeons and specialists.⁷

Conservative management methods exist and they involve leaving the placenta in the uterus and using medication, such as methotrexate, to help the placenta dissolve naturally. Another method is uterine artery embolisation, which is a procedure that blocks blood flow to the affected area of the uterus to minimise bleeding. The balloon occlusion catheter method also works in a similar way to block off blood flow to the affected uterine area to minimise haemorrhage.^6,7

A novel technique that aims to preserve the uterus using the balloon tamponade has also shown to be very effective in reducing the amount of blood loss and subsequent hysterectomies.⁸

These management strategies aim to minimise complications and address immediate concerns, highlighting the importance of specialised care and planning when handling PAS.

Impact on Fertility

Placenta accreta can impact fertility due to the often invasive and aggressive nature of the treatments utilised to manage the condition.

Hysterectomy 

Hysterectomy is the removal of the uterus which is commonly required to manage PAS. While it is a necessary and life-saving procedure in most cases, it also leads to permanent infertility.

Uterine damage and scarring

Surgical removal of the placenta may be the treatment of choice in some cases of PAS. This procedure can lead to damage to the uterine walls which lead to scarring and intrauterine adhesions called synechiae. These synechiae obstruct the uterine cavity and may interfere with future pregnancies.

Increased risk in future pregnancies

Women who have experienced placenta accreta are at a higher risk of recurrence of both PAS and placenta previa in future pregnancies, which would result in subsequent high-risk pregnancies.³

Psychological and emotional impact

Women with PAS are predisposed to post-traumatic stress disorder (PTSD) due to traumatic birth experiences. PAS is also associated with higher rates of depression and anxiety disorders which may persist long after delivery. For women who lost their fertility due to hysterectomies, there is an intense grieving and mourning period over the loss of their childbearing ability.⁹

Fertility Preservation Strategies

Fertility counselling and planning are crucial before delivery to discuss options for preserving fertility:

Conservative surgical management

• Expectant management is leaving the placenta in the uterus and allowing for spontaneous resorption. This method avoids surgical intervention, reducing the risk of damage to the uterus and severe haemorrhage. This may preserve the uterus for future pregnancies.
• Uterine artery embolisation and the use of methotrexate may help manage PAS conservatively. Embolisation blocks off the blood flow to the affected area, reducing bleeding and allowing resorption of the placenta. Methotrexate aids in dissolving the placenta.
• One-step conservative surgery is resection of only the section of the uterus invaded by the placenta. 
• Triple-P procedure involves pelvic devascularization, placental non-separation, and myometrial (muscular wall of the uterus) excision. This method focuses on removing the invasive placental tissue as well as preserving as much of the normal uterus as possible.¹⁰ 

Timing of future pregnancies

By allowing adequate time of around 6 to 12 months in between treatment of PAS and attempting the next pregnancy, may improve pregnancy outcomes. The interval allows the uterus to heal sufficiently to reduce the risk of future pregnancy complications.¹¹

Assisted reproductive technology (ART) 

Although ART can be a risk factor PAS, it still remains an option for future fertility. In vitro fertilisation (IVF) can be considered, especially for those who have undergone conservative surgical management.¹⁰ 

Surrogacy and adoption

Gestational surrogacy is where the embryo is implanted in another woman’s uterus, allowing women who cannot undergo pregnancy themselves to have genetically related children. However, this method of pregnancy is subject to various local laws and ethical considerations.

Adoption is another path to parenthood for women which provides an opportunity to raise children and build a family without the risks of pregnancy.

Summary

Placenta accreta spectrum (PAS) is a potentially life-threatening pregnancy condition that significantly impacts fertility. It is primarily associated with previous uterine surgeries, placenta previa, and advanced maternal age. Early diagnosis and multidisciplinary care coupled with careful planning and management are essential for managing the condition and minimising complications. Treatment often involves radical methods such as caesarean hysterectomy, which leads to permanent infertility. 

Women may experience psychological distress such as PTSD and depression due to traumatic birth experiences and loss of fertility associated with PAS. However, there are various fertility preservation strategies available such as conservative surgical techniques and the use of assisted reproductive techniques that may offer some hope. Fertility counselling and planning are important factors to be included in the conversation of care in women with PAS to address the complex challenges associated with the condition. Early detection, specialised care, and comprehensive fertility counselling are vital in managing PAS.