Around 2% of pregnant women have premature rupture of membranes

Researchers have identified a test which can predict whether a woman is likely to give birth if her waters break early in pregnancy.

High levels of lactate in vaginal fluid is strongly associated with onset of labour within 48 hours, according to Swedish researchers.

UK experts said the test would help to plan care and reassure women whose membranes rupture prematurely.

The study appears in Obstetrics and Gynaecology journal, BJOG.

Known as the "Lac-test", the tool was assessed in 86 women with singleton pregnancies of 20 to 36 weeks gestation.

When membranes rupture unexpectedly there's a big dilemma - do you deliver the baby or not, will this woman go into labour or not? Professor Andrew Shennan

Among 23 women with high lactate concentrations, 87% had spontaneous onset of labour within 48 hours.

In 58 women with low lactate concentrations - in effect a negative Lac-test - only 5% went into labour within 48 hours.

The median time between examination and onset of labour was 13.6 hours for those with a high lactate concentration and 48 days for those with a low lactate value.

Prediction

The researchers said previous studies had found an association between high lactate concentration in vaginal fluids and rupture of membranes in pregnancies of more than 34 weeks gestation, but this is the first time the link has been seen under 34 weeks.

Being able to predict labour is even more valuable in these premature babies, as steroids can be given to promote lung development and women can be referred to specialist hospitals.

Preterm prelabour rupture of membranes (PPROM) - waters breaking in pregnant women before 37 weeks - occurs in 2% of pregnancies and accounts for one-third of all preterm births.

Study leader, Dr Eva Wiberg-Itzel, from the Department of Clinical Science and Education at the Karolinska Institute, said: "The diagnosis of ruptured membranes is easy when there is an obvious leakage of amniotic fluid, but more difficult when the leak is scanty or intermittent.

"We believe that the Lac-test adds important information in clinical practice."

Professor Philip Steer, editor-in-chief of BJOG, said it seemed a promising tool to predict the onset of labour.

"A more reliable diagnosis of PPROM could help doctors determine when to keep women in hospital, and improve the timing of antenatal steroid therapy."

Professor Andrew Shennan, an obstetrician at St Thomas' Hospital in London, said the test could solve a potentially important problem.

"When membranes rupture unexpectedly there's a big dilemma - do you deliver the baby or not, will this woman go into labour or not?

"We would probably give steroids anyway as it's a high risk situation, but the main thing is being able to tell the women what's likely to happen.

"We can also get them to a specialist unit if needed."

Lung development can be a problem for premature babies

British researchers have identified a potential target for encouraging lung growth in babies in the womb.

A study in mice showed that a well-known molecule called the calcium receptor has a key role in the development of lungs in the foetus.

Drugs targeting the receptor are already available, the Cardiff University researchers said.

The results, which could lead to better outcomes for premature babies, are published in the Journal of Physiology.

If we can show that one of these drugs can modulate the action of the calcium receptor in the lung, it could be used to mature the lungs of a very premature baby as it grows Professor Paul Kemp, University of Cardiff

The final stages of lung development happen late in pregnancy so babies born prematurely can struggle to get enough oxygen and can develop chronic lung disease.

The latest research found that the calcium receptor "switches on" the growth of the lungs in the foetus.

In the study, the researchers were able to manipulate lung development by interrupting receptor function.

The next step is to carry out studies in individuals who have mutations in the calcium receptor which causes it to be permanently switched on or switched off, the researchers said.

"If that showed correlation between the mutation and post-natal lung health then we could move into clinical trials," said study author Professor Paul Kemp.

"The really exciting thing about the calcium receptor is that there are already drugs available that can alter its function.

"If we can show that one of these drugs can modulate the action of the calcium receptor in the lung, it could be used to mature the lungs of a very premature baby as it grows.

"An existing drug could potentially be approved much more quickly than a new one" he added.

He said the therapy could be something that is done in parallel with steroid treatment which is already given in babies at risk of being born early.

Annette Briley, research midwife for Tommy's, the baby charity said chronic lung disease is one of the major health problems facing premature babies, often presenting problems well into adulthood.

"Whilst this could be a promising breakthrough, it must be stressed that further rigorous randomised control tests must be carried out to assess the effectiveness of these drugs in premature babies."