What is PAS?

What is Placenta Accreta Spectrum (PAS)?

The placenta develops along with the baby in the womb (uterus) during pregnancy. It connects the baby to the mother’s blood supply and provides the baby with a source of oxygen and nourishment. It is effectively the baby's 'life-support machine'. Without a well functioning placenta, the baby cannot grow and develop normally. The placenta is delivered after the baby, and is sometimes called the afterbirth.

Rarely, placental development may be complicated by a problem known as placenta accreta spectrum (PAS: also known as abnormally adherent and invasive placenta). This is when the placenta grows too deeply into the wall of the womb, making separation at the time of birth difficult or impossible. This happens when the placenta implants over an area of scar tissue.

Who is at risk?

PAS is more commonly found in women with placenta praevia (placenta covering part or all of the opening to the womb (cervix)) who have previously had a caesarean delivery. Women who have had IVF, have a history of Asherman's syndrome or who have had PAS in a previous pregnancy are also at risk.

How is it diagnosed?

All women who have an anterior low lying placenta (implanted at the front of their womb) and who have also had a previous caesarean delivery should have a scan by a specialist who has expertise in diagnosing PAS to ensure that they are diagnosed before delivery. Their usual doctor should refer them to a specialist centre for this. If they do not volunteer to do this, you have the right to request it (see RCOG Guidelines)

PAS may be suspected in the antenatal period by an ultrasound scan, but while additional tests such as magnetic resonance imaging (MRI) scans may help with the diagnosis, your doctor will only be able to tell for sure if you have this condition by the findings at the time of delivery. Women who are strongly suspected to have PAS should be delivered in a specialist centre by a multi-disciplinary team who have expertise in managing this condition.

How is it managed?

PAS can cause significant bleeding if an attempt is made to remove your placenta. Therefore the usual plan is to leave the placenta untouched and perform a hysterectomy with it still inside (primary caesarean hysterectomy). Very occasionally it is only a small patch of placenta which is abnormal so it may be possible to just remove a small part of the womb which the placenta is stuck to (partial resection or uterine conserving surgery).

In the right circumstances, it may be possible to leave the placenta in place after birth, and allow it to absorb over the next few months. This is called conservative management or intentional placenta retention and can preserve the woman's fertility. However, it is not always successful as some women will bleed and so still need a hysterectomy. The exact type of management should be discussed with the team caring for you as each method is only suitable for a specific set of circumstances.

If PAS is suspected before your baby is born, your doctor will discuss your options and the extra care that you will need at delivery. Delivery may be planned earlier – for example between 34 and 37 weeks, depending on individual circumstances. You will need to have your baby in a hospital which offers specialist PAS management and has additional facilities available such as interventional radiology and extra blood transfusion products. Your doctor will be happy to discuss this with you.


How long should I expect to be in hospital?

This will depend on the type of management you have and whether you have any complications as a result of the delivery. Typically an-uncomplicated caesarean hysterectomy will need you to be in hospital between 3 and 5 days. A focal resection or conservative/expectant management should be less.

Will I be admitted before delivery, and for how long?

This will depend on individual circumstances but for a well woman with no complications (e.g. bleeding) who has good transport to get to hospital should it be needed, there is no need for routine admission to hospital before delivery but the final decision will be with your healthcare provider.

What are the long term impacts of hysterectomy on my health?

Unfortunately you will no longer be able to have any more children if you have had a hysterectomy and this, on top of everything you experience during your PAS journey, can affect your mental health. Please speak to you GP, community midwife or health visitor if you feel that this may be applicable to you as there is help available.

You will usually be left with your ovaries so should not become menopausal but there is some evidence that woman who have a hysterectomy go through the menopause a year or so earlier than they would otherwise have done (UK average age for menopause is 52).

A hysterectomy should not impact on your sex life. See this helpful web page on advice for sex after a hysterectomy.

The benefits are that you will no longer have any periods and you will not be able to get endometrial cancer or cervical cancer (if it was a total hysterectomy ie your cervix is also removed), so you will no longer need smear tests. You should also be able to have oestrogen-only HRT if you want it when you become menopausal and this is much easier to take than the combined HRT needed for women with a womb.

Will I be able to breastfeed?

You should be able to breastfeed unless you are having conservative management as deliberately retaining the whole placenta can sometimes stop your milk coming in.

If I don’t need a hysterectomy, will I be able to have more children?

Yes but if you have had a focal resection (part of the uterine wall removed) you will need to discuss this with your surgeon to find out how much womb they removed as removing a large amount may mean there is a much higher risk of complications including uterine rupture in subsequent pregnancies.

The evidence to date is that if the uterus is conserved 80% of women who wish to have another pregnancy will succeed in getting pregnant. Of those, about 20% (1:5) will go on to have another PAS.

What is the difference between 'mortality' and 'morbidity'

Mortality means death as a result of the condition or the treatment for it.

Morbidity means any medical issues that arise as a result of the condition or the treatment for it e.g. damage to the bladder or a large blood loss requiring blood transfusion.