Simple swab to tell which twins are really at risk of premature birth

A test developed by teams from Tommy’s London Research Centre can help predict whether twins will be born prematurely, a newly published study has found.

Tommy’s researchers can predict when twins will be born prematurely

27 April 2020

Half of twin pregnancies end in premature births, which raises the risk of serious complications – but as it’s very hard to predict when this will happen, many women endure costly drug treatments and anxious hospital stays only for their babies to arrive on time.

Researchers from Tommy’s London Research Centre at St Thomas’ Hospital have developed a test to predict premature birth by measuring levels of fetal fibronectin, a protein which acts like a glue to fix the amniotic sac to the womb lining. The team discovered that when a mother is at risk of giving birth prematurely, this protein is released into the vagina where it can be picked up with a swab.

The test is already used at Tommy’s Preterm Surveillance Clinic in St Thomas’ but is not currently part of standardised national guidelines for assessing women’s risk, which focus on measuring the cervix. Women can only get a fetal fibronectin test on the NHS if they have symptoms of early labour, such as cramps and backache – but up to 80% of these women are still pregnant a week later.

In a new study, Tommy’s researchers studied 144 women pregnant with twins and grouped them into low (up to 50ng/ml), mid (50-199ng/ml) and high (200ng/ml or above) fetal fibronectin levels. Three quarters of mothers in the high group gave birth before 30 weeks, compared to only 28.6% of those in the mid group. Under the current NHS test, which flags levels of 50ng/ml or more, these women would all be deemed equally high risk and given the same treatment – often involving a lengthy hospital stay and medications to prevent or prepare for premature birth.

The research team also found that high fetal fibronectin levels were a stronger warning sign than short cervix length, which is currently the standard NHS tool for premature birth screening. Of the women studied whose cervix was shorter than 25mm, 86% of those with the highest fetal fibronectin levels had their babies before 30 weeks, but nobody in the lowest group did.

Study author Andrew Shennan OBE, who is Professor of Obstetrics at King's College London and runs the Tommy’s Preterm Surveillance Clinic at Guy’s and St Thomas’, said: “Many women pregnant with twins don’t actually give birth prematurely, and this study shows that the typical NHS tests are not accurate enough to tell who is really at risk.

“Anyone using those tests has to err on the side of caution, and that can put undue strain on those mothers and on the NHS. As twins are increasingly common, there’s an urgent and growing need for better ways to predict that risk, so that precious resources can be focused on those most in need.”

Although the study found that testing fetal fibronectin levels of women between 22 and 27 weeks pregnant with twins could accurately predict whether they would be born early, the results of tests earlier in pregnancy were not significant.

The Tommy’s London Research Centre team has incorporated the findings into their QUIPP app, which accurately predicts the risk of premature birth, to ensure the right treatment is given to the right women at the right time.

In light of the research, campaigners are calling for the test to be standard practice across the NHS, so that doctors could tailor maternity care to better support high risk women and reassure those who are unduly worried – reducing the economic and emotional costs of unnecessary drug treatments and hospital admissions under the current system.

Tommy’s chief executive Jane Brewin said: “With 60,000 babies born prematurely each year in the UK, this test can reassure women who may otherwise be very anxious about their risk of giving birth early, and may be able to make pregnancy safer for those who do need special care.

“Everyone should be able to benefit from this pioneering and potentially lifesaving tool, and we urge the Government to include these tests as standard in national maternity care guidelines, so that precious NHS resources can be focused on those most in need.”

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