By: 21 June 2017
New diagnostic test for amniotic leaks

Paul Stillman looks at methods to test the risks when amniotic leaks occur during pregnancy

Symptoms of vaginal wetness is common during pregnancy. Around 20 per cent of pregnant women report to hospital [1] or birth units reporting the sensation of wetness. In most cases it is harmless, resulting from urinary incontinence or changes to the vaginal mucus. However, dampness may indicate a premature rupture of the membranes (PROM). This requires medical attention as there is a risk of both infection and the early onset of labour.

Unless there is an obvious rupture of the membranes, a speculum examination will be performed to determine if there is any pooling of amniotic fluid. It is not standard NHS practice to use acidity or Ferning tests to confirm any pooling is amniotic fluid. In around 50 per cent of cases, the wetness is urine and the patient may be reassured and return home. [2] However current testing methods do not always detect small ruptures and hind leaks, which is of concern for all maternity and midwifery professionals, as any leak of amniotic fluid increases the risk of a serious neonatal infection (1 per cent compared to 0.5 per cent for women with intact membranes) and early onset of labour, in that 60 per cent of affected women will go into labour within 24 hours. [3]


New test offers prompt and accurate diagnosis of amniotic leaks

AmnioSense, is a new evidence-based diagnostic test which has been proven to be as accurate as hospital-based examinations (Ferning test, sterile speculum examination and pH test). It is a thin pantyliner filled with a central polymer-embedded strip which can be worn for up to 12 hours to ensure continuous monitoring. The strip changes colour from yellow to blue or green when it comes into contact with any fluid which has a pH of more than 6.5, as is the case with amniotic fluid. [4] Crucially, AmnioSense can detect as little as 100 microliters of amniotic fluid — the equivalent of two drops. Unlike a speculum examination, AmnioSense allows for constant monitoring and ensures small, difficult to diagnose ruptures, such as hind leaks, are detected. AmnioSense provides reassurance and an early warning for pregnant women.


Supporting science summary

Several studies have confirmed the accuracy, sensitivity and ease of use of Amniosense. Samples of amniotic fluid taken from 50 women, between 16 and 23 weeks gestation, who were undergoing checks for foetal abnormalities showed that in all cases the AmnioSense test gave a positive response to the presence of amniotic fluid. The results could be read for up to 12 hours, [5] which is important in a real-world setting as a woman could carry out the test at home, and still have time to get to her midwife or healthcare provider and show them the result while it was still reliable.

A further study involving 339 women attending hospital with unexplained vaginal wetness found that AmnioSense correctly detected 154 of the 161 cases where a leak of amniotic fluid was confirmed.[6]

A UK study looked at 157 women attending the antenatal unit at St Thomas’ Hospital in London with a suspected leak of amniotic fluid. AmnioSense detected 98 per cent of leaks caused by urine and harmless vaginal discharges and 67 per cent of cases where there was a leak of amniotic fluid. Two out of five cases of rupture (38 per cent) could have been diagnosed without the need for a speculum examination which can itself increase the risk of infection. [7] The researchers concluded that: “If Amniosense is used in clinical practice, the reduction in the number of speculum examinations will substantially benefit women and service providers.”

Another study reviewing AmnioSense compared results from 103 women, aged 18 to 45, attending the labour and delivery ward of a university-affiliated hospital in Israel. A third had suspected leaks, rupture was confirmed in another third and the remaining third had no symptoms and provided a control group. [8] Of the 34 women with suspected leaks, rupture of the membranes was confirmed in 10 cases and every one was correctly identified by the AmnioSense pantyliner.

Appraisal by the National Institute for Health and Care Excellence (NICE) [9] concluded AmnioSense is sufficiently accurate to exclude a leak of amniotic fluid, would avoid unnecessary speculum examinations and has the potential to generate cost savings. NICE concluded that 42 per cent of these examinations would be unnecessary if AmnioSense were used as a simple prenatal triage measure to rule out leaks caused by vaginal mucus or urine. Based on the evidence, NICE has recommended the adoption of AmnioSense within clinical practice in the community.

In conclusion, timely adoption of AmnioSense would provide reassurance and clear benefits for both maternity and midwifery healthcare professionals and women with suspected PROM.

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[1] The summary was published in Hygeia Foundation, Inc. and Institute for Perinatal Loss. Premature Rupture of the Fetal Membranes Vol.2 No.4

by Kunle Odunsi M.D., and Paolo Rinaudo, M.D. Yale-New Haven Hospital.

[2] Ref needed

[3] NICE Clinical guideline CG190 Intrapartum care for healthy women and babies.

[4] NICE Medical Technology Guidance on file

[5] Marwan Odeh and Borstein J AL-SENSE IJCM20110300017_39572450[1]

[6] Effectiveness of a novel home-based testing device for the detection of rupture of membranes. Bornstein J, Ohel G, Sorokin Y, Reape KZ, Shnaider O, Kessary-Shoham H, Ophir E. Am J Perinatol. 2009 Jan;26(1):45-50.

[7] Mulhair L Prospective cohort study – AmnioSense Int J Obstet & Gynecol 2008

[8] Bornstein J Nonintrusive Diagnosis AL-SENSE Am J Printol 2006 on file