The technology

AmnioSense (Common Sense Ltd) is a non-invasive diagnostic pad. The pad is designed to assess unexplained vaginal wetness during pregnancy. Vaginal wetness can result from leaking amniotic fluid and may indicate amniotic membrane rupture. Premature membrane rupture needs urgent medical attention.

AmnioSense attaches to underwear and can be worn for up to 12 hours. The liner has a central polymer-embedded strip which changes colour when it comes into contact with fluid of pH 6.5 or higher. A healthy vagina has a pH value of 3.5 to 4.5 but amniotic fluid and urine have pH values higher than 6.5. When in contact with urine or amniotic fluid, the central strip changes colour from yellow to blue or green. If ammonia is present above a certain level, the strip reverts to yellow within 15 minutes, distinguishing urine from amniotic fluid. When wetness is felt, the liner is removed and left to dry. If after 15 minutes the colour of the strip is blue, green or grey, the user should seek medical attention. In the presence of amniotic fluid, the colour of the liner will stay changed for up to 2 hours.


AmnioSense is a non-invasive technology that aims to detect amniotic fluid in small volumes of vaginal wetness over a long period of time. The technology is currently the only home test for the detection of amniotic fluid. Standard care for pregnant women experiencing unexplained vaginal wetness is an invasive procedure to check that the amniotic membrane is intact.

Current care pathway

NICE's guideline on intrapartum care recommends that women experiencing unidentified vaginal wetness have a speculum examination to detect ruptured amniotic membranes in cases where the cause for vaginal wetness is unclear. Before the procedure, the woman is asked to lie down for 30 minutes to allow for pooling of amniotic fluid. A speculum is then used to examine the vagina and detect any pooling of amniotic fluid. Where pooling is present, the woman is diagnosed with ruptured membranes and her condition is managed accordingly. Where no pooling is detected, it is assumed the membranes are still intact and the woman may be discharged. The total time to complete a speculum examination, including time allowed for amniotic pooling, is up to 1 hour. Diagnosis confirmation may be sought through nitrazine (pH) testing, amniotic fluid crystallisation testing (fern testing), biomarker testing and ultrasound examination of the uterus. However, these assessments are not routine practice in the NHS.

Population, setting and intended user

AmnioSense is intended for pregnant women who have unexplained vaginal wetness. The technology is targeted towards women who are in their second or third trimester of pregnancy.

The technology is designed to be used by primary and community care clinical staff or at home by pregnant women. Instructions for use of the technology are included in the packaging.


The technology costs £1.59 per pad, excluding VAT, and is sold in boxes of 12 or 50 individually sealed pads. Women who have a positive test result using AmnioSense will need a speculum examination.

Costs of standard care

The cost of a disposable speculum is £0.89. As well as the cost of the speculum, there is also a cost associated with the procedure. The approximate cost of the procedure is £65 according to the NHS reference costs 2017/18 for specialised fetal invasive diagnostic procedures.

Resource consequences

AmnioSense has been launched in the UK. The cost of the technology is greater than standard of care. The company anticipates the technology will be resource releasing for the NHS because of fewer speculum examinations, the need for fewer higher-grade staff and a shift in care setting from secondary to primary and community. Instructions for using the technology are included in the cost, no additional training is needed.