Placenta Accreta Spectrum is a rare pregnancy complication which poses a risk to both mother and baby.
Currently, PAS cases are identified through ultrasounds, MRIs, and other predictive confounding conditions – such as previous caesarean section – but these methods aren’t foolproof and between 33-50% of PAS cases remain undetected prior to delivery.
Now, researchers from the Brigham and Women’s Hospital (BWH) in the US have discovered unique circulating microparticle (CMP) proteins in pregnant women which can predict PAS as early as the second trimester of pregnancy (13-26 weeks).
The results, which have been published in Scientific Reports, detail the first steps on the road to creating a targeted blood test for predicting PAS.
“PAS is a significant contributor to maternal morbidity and mortality worldwide,” says first author Dr Hope Yu, a Maternal-Foetal Medicine physician in the Department of Obstetrics and Gynecology at BWH.
“Before our study, up to half of these cases weren’t able to be detected before delivery. Our study aims to improve that detection rate using a blood test and to eventually improve health outcomes worldwide.”
What is placenta accreta spectrum?
In PAS the decidua layer of the uterus – the mucosal lining that forms every month in preparation for pregnancy and forms the maternal part of the placenta – is patchy or completely absent. This causes the placenta to become stuck, or even to grow into, the muscle layer of the uterus.
PAS is actually a spectrum of three disorders:
- Placenta accreta – the placenta is stuck directly onto the muscle of the uterus
- Placenta increta – the placenta grows into the muscle of the uterus
- Placenta percreta – the placenta grows through the uterus and into other organs like the bladder and bowel
As a result, it doesn’t come away easily after birth, which can cause serious haemorrhaging. This may result in the need to give birth early, caesarean section birth, blood transfusions due to heavy bleeding, or even hysterectomy in order to stop the bleeding.
Read more: Patchwork placenta.
PAS occurs in around 3 per 1,000 births in Australia, but has become more common – up from 1 per 1,000 births in the 1970s – because having a previous caesarean section increases the risk of developing it.
“It is so important to identify these cases prior to delivery,” says Yu. “If we can identify a PAS case during pregnancy, the patient can then make a potentially life-saving choice to deliver in a tertiary delivery centre with specialised providers.
“Having an experienced, multidisciplinary team by your side during a PAS birth can make an enormous difference when it comes to mortality and morbidity outcomes.”
Certain CMP proteins predict PAS before delivery
The team looked at proteins associated with circulating microparticles (CMPs) – tiny vesicles that exist outside of cells and which the cells use to communicate with one another.
They studied the CMPs at the maternal-foetal interface of the placenta by studying blood plasma samples from 35 PAS patients and 70 control patients (all retroactively diagnosed after delivery) at 26 weeks (second trimester) and 35 weeks (third trimester).
Isolating and identifying CMP associated proteins revealed five that distinguished PAS patients from control patients at 26 weeks, and four at 35 weeks – indicators which could enable safe prediction of PAS well before delivery.
The authors say that more research and clinical trials will be needed but their next steps will involve widening the patient sample size and creating a standardised commercial test.
“This is another step toward proactive, personalised prenatal care,” concludes senior author Thomas McElrath, MD, PhD, also a Maternal-Foetal Medicine physician at BWH.
“Right now, prenatal care too often assumes that every person has the same risks of complications during pregnancy. To be able to personalise and make each patient’s care profile particular to their needs is the ultimate goal.”