By Community Midwife, Emma Herbert
Even the most straightforward pregnancy can be a time of increased anxiety for pregnant women. As midwives, we are often the first port of call for women to voice their concerns and look for reassurance. Usually, we are able to set their minds at rest with a few simple words of information or advice. Other times, we may need to recommend some kind of intervention or further investigation.
Vaginal wetness is common during pregnancy. There are around 696,000 live births in England and Wales every year (Office for National Statistics 2016) and approximately one third of those women will notice some sort of leak during pregnancy (Chartered Society of Physiotherapy 2014). Twenty per cent of pregnant women report to hospital or birth units reporting wetness (Odunsi et al 2017) and many more will brush it off as a small leak of urine. In most cases, it is harmless, resulting from urinary incontinence or changes to the vaginal secretions. However, dampness could indicate a rupture of the membranes. Waters do not always break with an obvious ‘rush’.
Estimates vary, and are complicated by differing definitions of premature rupture of membranes (PROM) in the UK and US, but as many as one in ten pregnancies is complicated by PROM (Bornstein et al 2006) and in three out of five cases women go into labour within 24 hours (National Institute for Health and Care Excellence (NICE) 2016). PROM and P-PROM (preterm rupture of membranes) are a factor in two out of five cases of babies being born too early and can be fatal on three counts: prematurity, sepsis and pulmonary hypoplasia, where the lungs have not fully formed and babies cannot breathe without assistance (Porter 1999). For women, there is the risk of infection and other potentially serious problems including retained placenta and postpartum haemorrhage.
Benefits of AmnioSense
- Detects even minimal amounts of amniotic leaks
- Clearly distinguishes between amniotic leakage and urine
- Non-intrusive — a reduction in unnecessary speculum examinations
- A reduced risk of infection from speculum examination, particularly if repeat examinations are required
- A reduction in the time spent in hospital. Women who currently undergo a speculum examination need to remain in hospital for approximately 30 minutes before the procedure and 45 to 60 minutes in total (without wait times). Women using AmnioSense in a clinical setting will not require a hospital bed and can undergo the test as an outpatient or in a community setting. Furthermore, women who are already known to be at increased risk of PROM/P-PROM can use the test at home
- Easy to use one-step test: test results can be interpreted by looking at the indicator strip and do require a colour scale.
- Stable colour for at least two hours
- Reassurance and peace of mind.
Now, I can avoid all of that in many instances. AmnioSense is a new, evidence-based non-invasive test for detecting amniotic fluid. It has been analysed and tested by several independent clinical studies and reviews, all confirming its efficacy and accuracy (Bornstein et al 2006, Bornstein et al 2009, NICE 2013).
The product, which takes the form of a pantyliner, contains a two-stage diagnostic polymer strip that can tell if a pregnant woman is leaking amniotic fluid. It has been proven to be as accurate as hospital-based tests when compared to the most common tests performed in hospital — sterile speculum examination, microscopic ferning test and pH paper test — and the National Institute for Health and Clinical Excellence (NICE) concluded that using AmnioSense alongside appropriate changes to clinical practice in the community should be encouraged (NICE 2013).
Below are the key steps for using AmnioSense
1) A pregnant woman should attach the AmnioSense liner to her underwear. The pale yellow indicator strip should sit directly against the vagina.
2) The user should wear the liner as she would a normal pantyliner until she feels wetness.
3) At the first sense of vaginal wetness, the user should remove the liner and wait 10 minutes before reading the result.
4) After 10 minutes the user should check for a colour change on the yellow background of the liner.
5) Result reading:
Positive results: If there is a colour change, partial or complete, to blue or green (any intensity) in any size, shape or location on the pantyliner, the vaginal wetness is probably caused by amniotic fluid.
Negative results: If the pantyliner did not change colour (remained yellow or turned yellow after 10 minutes), the vaginal wetness was probably not caused by amniotic fluid and may be urine.
AmnioSense is intended for use by women at any stage of pregnancy who have unidentified vaginal wetness and by those at high risk of PROM. The studies show that there are several potential applications for AminoSense, including use in triage, to identify ‘leaks’ which are caused by urinary incontinence or an increase in harmless vaginal secretion, and to reserve speculum examination only for those women who have a positive result using the AmnioSense test.
As the NICE technology appraisal points out, this would save 42% of the speculum examinations currently carried out to determine whether or not there is a rupture of the membranes (NICE 2013).
Those who are at increased risk of PROM/P-PROM are:
- Women who have experienced PROM during a previous pregnancy (O’Connor et al 1999).
- Women expecting more than one baby.
- Women who have undergone cervical surgery — such as a cone biopsy or laser (Bornstein et al 2009, Cancer Research UK 2017).
- Those with a shorter cervix (Institute of Medicine 2007).
- Some placental problems can lead to a rupture and tests such as amniocentesis and CVS also carry a small risk.
- Women with diabetes (NICE 2015).
- Those who are overweight. A BMI of between 25 and 30 is associated with a 21% increase in premature rupture; a BMI of 30 to under 35 upped the odds to 27%; 35 to less than 40 raised the threat by 35% and a BMI of more than 40 increased the risk by 52% (Cnattingius et al 2013, NICE 2016).
- Women with poor nutrition and low haemoglobin — which is caused by iron deficiency — has been linked to PROM (Zhang et al 2009). Some researchers believe that having low levels of vitamins C and E increases the risk of early rupture (Woods et al 2001).
- Smokers — smoking is another risk factor, particularly early in the pregnancy. A large Canadian study, which analysed data from 17,961 births, found that smoking more than 10 cigarettes a day significantly increases the danger of a woman’s waters breaking too soon (England et al 2013).
- Women with endometriosis — endometriosis has also been shown to increase the risk of a premature rupture (Harada et al 2016). Although it affects one in 10 women of child-bearing age, endometriosis is difficult to detect and on average women have to wait 7.5 years from the time they seek help to a confirmed diagnosis.
- Women with Asherman’s syndrome, which is characterised by adhesions and scarring of the womb lining. It is not clear how many women may be affected by Asherman’s, but having a previous miscarriage or dilation and curettage (D&C) increases the risk.
I use these new diagnostic liners both with women who have had vaginal wetness and also with patients who are at increased risk of PROM. To date at least 100 of my patients have already directly benefited.
How does it work?
Amniotic fluid has a pH of 6.7 or more, and if the strip comes into contact with moisture with a pH of more than 6.5 it will turn a blue-green colour. Urine has a pH of between 4 and 8, so can cause a colour change, but ammonia causes a reagent to return the liner to its original colour within 10 minutes. If the result is caused by amniotic fluid the blue-green colour will remain for at least two hours, giving time for the woman to get to a GP, antenatal clinic or A&E before it fades. Using AminoSense means that both health care professionals and the expectant mother can be confident that any leaks of amniotic fluid will be quickly identified.
The proof of principle test showed AmnioSense was 100% effective at identifying amniotic fluid. This was demonstrated beyond doubt by using samples of amniotic fluid taken from 50 women, between 16 and 23 weeks’ gestation, who were undergoing checks for fetal abnormalities. In all cases, the AmnioSense test gave a positive response to the presence of amniotic fluid with 100% accuracy (Porter 1999, Bornstein et al 2006).
In its conclusion, NICE also reported that AmnioSense is sufficiently accurate to exclude a leak of amniotic fluid, would avoid unnecessary speculum examinations and has the potential to generate cost savings. Based on the evidence, NICE has recommended the adoption of AmnioSense within clinical practice in the community (NICE 2013).
‘The feedback I have had from women who have tried AmnioSense is that it can take some of the worry out of pregnancy by providing a simple and accurate home test to confirm whether or not their waters have broken. AmnioSense provides them with peace of mind. I think it’s a really valuable tool for midwives to improve pregnancy outcomes’. (Observation by author)
American Pregnancy Association (2017). Low amniotic fluid levels: oligohydramnios. http://americanpregnancy.org/pregnancy-complications/oligohydramnios [Accessed 26 October 2017].
Bornstein J, Geva A, Solt I et al (2006). Nonintrusive diagnosis of premature ruptured amniotic membranes using a novel polymer. Am J Perinatol 23(6):351-4.
Bornstein J, Ohel G, Sorokin Y et al (2009). Effectiveness of a novel home-based testing device for the detection of rupture of membranes. Am J Perinatol 26(1):45-50.
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