Rupture of Membranes
Procedure: Fern and Nitrazine Tests
(These processes have been deemed unbillable in US but may still be in use elsewhere)
1. Insert speculum for sample collection, avoid the use of lubricant.
2. Collect vaginal secretion from the posterior vaginal pool with two cotton sterile swabs.
Do not touch the mucus plug in the cervix.
Do not contaminate the specimen with saline/koh.
3. After collection, immediately rub the swab against a glass slide, creating a very thin smear, do not apply a coverslip.
4. Allow slide to dry for 5-10 minutes.
5. Using a microscope, examine the dried smear under 10X power without a cover slip.
6. If present, saline in the amniotic fluid crystallizes to form a fern-like pattern.
The Fern Test should be performed in conjunction with the Nitrazine Test.
1. Tear off a 2-3 cm piece of Nitrazine paper.
2. Apply fluid collected from the vaginal pool directly to the paper.
3. A blue color change is consistent with amniotic fluid pH of 7-7.5. The Nitrazine paper container includes a chart of color change and pH.
1. Tear off a 2-3 cm piece of Nitrazine paper.
2. Apply fluid collected from the vaginal pool directly to the paper.
3. A blue color change is consistent with amniotic fluid pH of 7-7.5. The Nitrazine paper container includes a chart of color change and pH.
Rupture of membranes is confirmed with either:
1) Presence of pooled vaginal fluid on speculum exam
2) Positive Ferning and Nitrazine tests
If the Nitrazine Test and Fern Test are positive, probable membrane rupture has occurred.
False Positives
Nitrazine Test
Cervical mucus
Blood
Vaginal infection (BV)
Semen
Ferning Test
Cervical mucus
Blood
Urine
Saline
False Negative
ROM> 24 hours.
1) Presence of pooled vaginal fluid on speculum exam
2) Positive Ferning and Nitrazine tests
If the Nitrazine Test and Fern Test are positive, probable membrane rupture has occurred.
False Positives
Nitrazine Test
Cervical mucus
Blood
Vaginal infection (BV)
Semen
Ferning Test
Cervical mucus
Blood
Urine
Saline
False Negative
ROM> 24 hours.