New study promises end to fatal placenta deliveries

It is every woman’s dream to have a healthy pregnancy and successful delivery.

But sometimes, these desires may not be fulfilled due to unpredictable complications.

One such complication is a condition known as placental accreta, which is one of the most dangerous risks pregnant women can face as their delivery date approaches.

In normal childbirth, the placenta, which sustains foetal development during pregnancy is delivered shortly after the newborn infant.

But in mothers with the condition, it becomes attached to their uterusmaking difficult to remove the placenta without causing massive, and sometimes fatal bleeding.

This can adversely affect the health of affected mothers and put their lives at risk.

In most cases, the emergency surgery (hysterectomy) needed to save the mother's life can leave her unable to have more children as doctors usually remove the uterus.

Since placenta accreta often presents with no signs or symptoms many women may not be aware they have it until they arrive at the hospital for delivery.

This makes it difficult for clinicians to effectively plan for surgical operations that minimise risks to mothers.

It also leads to a greater risk of haemorrhage (excessive bleeding), which can result in shock and death for affected mothers delivering in poorly equiped and staffed hospitals.

To address these challenges, scientists have been trying to find ways of identifying women at risk of placenta accreta early enough.

A new study, published in this month in the Science Immunology Journal has made inroads into this matter.

The research makes a surprising connection between placental accreta risk and a gene mutation that prevents the healthy formation of Natural Killer (NK) cells - a type of white blood cells.

The NK cells, which help the body to fight off cancer tumours and viral infections, also plays a key role in preventing the placenta from attaching itself so deeply in the uterus after the initial stages of pregnancy.

During the study, researchers from the Cincinnati Children's Division of Immunobiology observed an abnormally high frequency of pregnant mice in one of their colonies having unsuccessful pregnancies.

They found that the affected mice were experiencing retained placentas which was reflective of the human placental accreta condition.

This was something rarely seen in mice. It therefore prompted a new investigation into the occurrence.

Eventually, the researchers discovered that the mice carried a mutation (in a protein called Gab3), which prevented normal NK cell expansion in the uterus.

The disrupted NK cells then failed to do the important job of turning off the process that allows growing embryos to attach to tissues inside the uterus.

During pregnancy, the foetus usually attaches itself to tissues in the uterus. But after about 20 weeks, the NK cells come in to forestall further attachment hence making it possible for the mother to have a safe delivery where the placenta comes out shortly after birth.

"For normal placental development to occur, the growth of fetal cells must be held in check by NK cells," said Kasper Hoebe, the lead author of the study.

With this new discovery, the researchers note that doctors could begin screening women to determine if they have malfunctioning NK Cells.

“If future studies confirm that women facing accreta also have malfunctioning NK cells, it may become possible to prevent over-attachment and reduce the need for fertility-ending surgeries (hysterectomies),” states Helen Jones, co-author of the study and expert in placenta research at Cincinnati Children's.

One way of preventing the over attachment of embryos to the uterine walls, could be through an NK Cell transplant to rid affected mothers of existing mutations before they conceive.

Dr Jones, however, notes that much more research must be done before women can be tested to determine if they have malfunctioning NK cells, and if an NK cell transplant would be safe and effective.

Even though the NK cells have been transplanted to treat people with certain forms of cancer, the potential impacts on a pregnancy are not yet known.

"We don't know yet because we still need to investigate this in humans. We are working now on an international collaboration to try to work this out," Jones says.

Having multiple caesarean sections (C-sections) is considered as a major risk factor for the placenta accreta.

Sometimes, however, the condition occurs without a history of uterine surgery.