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Ferning in amniotic fluid: Is it a useful indicator of ruptured membranes?
YES. The presence of arborized crystals (ferning) in amniotic fluid is both sensitive (74%-100%) and specific (77%-100%) for diagnosing rupture of membranes in laboring women who report loss of fluid (strength of recommendation [SOR]: A, multiple prospective cohort studies). However, it is much less sensitive and specific for women with fluid loss who aren’t in labor (SOR: B, 1 prospective cohort study).
Gross contamination of amniotic fluid with blood or antiseptic solutions may decrease the diagnostic accuracy of ferning, whereas contamination with meconium doesn’t (SOR: C, bench research).
Evidence summary
A nonsystematic review of 11 prospective cohort studies (N=2804) reported that ferning was both sensitive and specific for the presence of amniotic fluid in laboring women who reported fluid loss. Labor was defined as contractions with subsequent delivery of a baby. Ferning had a mean sensitivity of 96% (range, 74%-100%) and a mean specificity of 96.2% (range, 77%-100%).1
Helpful in laboring women, but less so in those who are nonlaboring
A prospective cohort study evaluated the sensitivity and specificity of ferning among women reporting fluid loss who were in labor compared with women who weren’t in labor. Investigators classified laboring women (n=51) as having continued fluid loss and no fetal membranes covering the presenting part and progressing to delivery. They considered women to be nonlaboring (n=100) if they had minimal fluid loss and fetal membranes covering the presenting part or didn’t progress to delivery (investigators diagnosed 39 women with ruptured membranes on clinical grounds). Ferning was 98% sensitive and 88.2% specific in laboring women, and 51.3% sensitive and 70.5% specific in nonlaboring women.1
Ferning occurs from 14 weeks of gestation onward
A prospective case series (N=400) determined that amniotic fluid would fern at all gestational ages between 14 and 41 weeks. Investigators obtained fluid samples by amniocentesis and confirmed that they were 100% nitrazine-positive.2 They found more consistent ferning in samples dried on a slide for 10 minutes than samples dried over a flame (100% vs 86.7% of 112 samples).
Some contaminants in amniotic samples affect ferning
In vitro studies evaluated ferning in samples of amniotic fluid mixed with blood, meconium, or vaginal fluids. Blood contamination didn’t affect ferning unless the sample contained more than 10% blood.3-5 Meconium (which itself verifies ruptured membranes) didn’t change the fern pattern at any dilution,6 nor did vaginal discharge.3
Antiseptic solution may cause false-positive results, as may semen, fingerprints, and cervical mucus—although none of these show the fine arborization or discrete crystallization seen in uncontaminated amniotic fluid.6,7
Recommendations
The American College of Obstetricians and Gynecologists says that ferning is a confirmatory test for ruptured membranes, to be used along with pooling in the vaginal vault, and that premature membrane rupture is confirmed by fluid passing from the cervical canal.8
1. De Haan HH, Offermans PM, Smits F, et al. Value of the fern test to confirm or reject the diagnosis of ruptured membranes is modest in nonlaboring women presenting with nonspecific vaginal fluid loss. Am J Perinatol. 1994;11:46-50.
2. Bennett SL, Cullen JB, Sherer DM, et al. The ferning and nitrazine tests of amniotic fluid between 12 and 41 weeks gestation. Am J Perinatol. 1993;10:101-104.
3. Brookes C, Shand K, Jones WR. A reevaluation of the ferning test to detect ruptured membranes. Aust N Z J Obstet Gynaecol. 1986;26:260-264.
4. Reece EA, Chervenak FA, Moya FR, et al. Amniotic fluid arborization: effect of blood, meconium, and pH alterations. Obstet Gynecol. 1984;64:248-250.
5. Rosemond RL, Lombardi SJ, Boehm FH. Ferning of amniotic fluid contaminated with blood. Obstet Gyncol. 1990;75:338-340.
6. McGregor JA, Johnson S. “Fig leaf” ferning and positive nitrazine testing: semen as a cause of misdiagnosis of premature rupture of membranes. Am J Obstet Gynecol. 1985;151:1142-1143.
7. Lodeiro JG, Hsieh KA, Byers JH, et al. The fingerprint, a false-positive fern test. Obstet Gynecol. 1989;73:873-874.
8. American College of Obstetricians and Gynecologists. Premature rupture of membranes. ACOG Practice Bulletin No. 80. Obstet Gynecol. 2007;109:1007-1019.
YES. The presence of arborized crystals (ferning) in amniotic fluid is both sensitive (74%-100%) and specific (77%-100%) for diagnosing rupture of membranes in laboring women who report loss of fluid (strength of recommendation [SOR]: A, multiple prospective cohort studies). However, it is much less sensitive and specific for women with fluid loss who aren’t in labor (SOR: B, 1 prospective cohort study).
Gross contamination of amniotic fluid with blood or antiseptic solutions may decrease the diagnostic accuracy of ferning, whereas contamination with meconium doesn’t (SOR: C, bench research).
Evidence summary
A nonsystematic review of 11 prospective cohort studies (N=2804) reported that ferning was both sensitive and specific for the presence of amniotic fluid in laboring women who reported fluid loss. Labor was defined as contractions with subsequent delivery of a baby. Ferning had a mean sensitivity of 96% (range, 74%-100%) and a mean specificity of 96.2% (range, 77%-100%).1
Helpful in laboring women, but less so in those who are nonlaboring
A prospective cohort study evaluated the sensitivity and specificity of ferning among women reporting fluid loss who were in labor compared with women who weren’t in labor. Investigators classified laboring women (n=51) as having continued fluid loss and no fetal membranes covering the presenting part and progressing to delivery. They considered women to be nonlaboring (n=100) if they had minimal fluid loss and fetal membranes covering the presenting part or didn’t progress to delivery (investigators diagnosed 39 women with ruptured membranes on clinical grounds). Ferning was 98% sensitive and 88.2% specific in laboring women, and 51.3% sensitive and 70.5% specific in nonlaboring women.1
Ferning occurs from 14 weeks of gestation onward
A prospective case series (N=400) determined that amniotic fluid would fern at all gestational ages between 14 and 41 weeks. Investigators obtained fluid samples by amniocentesis and confirmed that they were 100% nitrazine-positive.2 They found more consistent ferning in samples dried on a slide for 10 minutes than samples dried over a flame (100% vs 86.7% of 112 samples).
Some contaminants in amniotic samples affect ferning
In vitro studies evaluated ferning in samples of amniotic fluid mixed with blood, meconium, or vaginal fluids. Blood contamination didn’t affect ferning unless the sample contained more than 10% blood.3-5 Meconium (which itself verifies ruptured membranes) didn’t change the fern pattern at any dilution,6 nor did vaginal discharge.3
Antiseptic solution may cause false-positive results, as may semen, fingerprints, and cervical mucus—although none of these show the fine arborization or discrete crystallization seen in uncontaminated amniotic fluid.6,7
Recommendations
The American College of Obstetricians and Gynecologists says that ferning is a confirmatory test for ruptured membranes, to be used along with pooling in the vaginal vault, and that premature membrane rupture is confirmed by fluid passing from the cervical canal.8
YES. The presence of arborized crystals (ferning) in amniotic fluid is both sensitive (74%-100%) and specific (77%-100%) for diagnosing rupture of membranes in laboring women who report loss of fluid (strength of recommendation [SOR]: A, multiple prospective cohort studies). However, it is much less sensitive and specific for women with fluid loss who aren’t in labor (SOR: B, 1 prospective cohort study).
Gross contamination of amniotic fluid with blood or antiseptic solutions may decrease the diagnostic accuracy of ferning, whereas contamination with meconium doesn’t (SOR: C, bench research).
Evidence summary
A nonsystematic review of 11 prospective cohort studies (N=2804) reported that ferning was both sensitive and specific for the presence of amniotic fluid in laboring women who reported fluid loss. Labor was defined as contractions with subsequent delivery of a baby. Ferning had a mean sensitivity of 96% (range, 74%-100%) and a mean specificity of 96.2% (range, 77%-100%).1
Helpful in laboring women, but less so in those who are nonlaboring
A prospective cohort study evaluated the sensitivity and specificity of ferning among women reporting fluid loss who were in labor compared with women who weren’t in labor. Investigators classified laboring women (n=51) as having continued fluid loss and no fetal membranes covering the presenting part and progressing to delivery. They considered women to be nonlaboring (n=100) if they had minimal fluid loss and fetal membranes covering the presenting part or didn’t progress to delivery (investigators diagnosed 39 women with ruptured membranes on clinical grounds). Ferning was 98% sensitive and 88.2% specific in laboring women, and 51.3% sensitive and 70.5% specific in nonlaboring women.1
Ferning occurs from 14 weeks of gestation onward
A prospective case series (N=400) determined that amniotic fluid would fern at all gestational ages between 14 and 41 weeks. Investigators obtained fluid samples by amniocentesis and confirmed that they were 100% nitrazine-positive.2 They found more consistent ferning in samples dried on a slide for 10 minutes than samples dried over a flame (100% vs 86.7% of 112 samples).
Some contaminants in amniotic samples affect ferning
In vitro studies evaluated ferning in samples of amniotic fluid mixed with blood, meconium, or vaginal fluids. Blood contamination didn’t affect ferning unless the sample contained more than 10% blood.3-5 Meconium (which itself verifies ruptured membranes) didn’t change the fern pattern at any dilution,6 nor did vaginal discharge.3
Antiseptic solution may cause false-positive results, as may semen, fingerprints, and cervical mucus—although none of these show the fine arborization or discrete crystallization seen in uncontaminated amniotic fluid.6,7
Recommendations
The American College of Obstetricians and Gynecologists says that ferning is a confirmatory test for ruptured membranes, to be used along with pooling in the vaginal vault, and that premature membrane rupture is confirmed by fluid passing from the cervical canal.8
1. De Haan HH, Offermans PM, Smits F, et al. Value of the fern test to confirm or reject the diagnosis of ruptured membranes is modest in nonlaboring women presenting with nonspecific vaginal fluid loss. Am J Perinatol. 1994;11:46-50.
2. Bennett SL, Cullen JB, Sherer DM, et al. The ferning and nitrazine tests of amniotic fluid between 12 and 41 weeks gestation. Am J Perinatol. 1993;10:101-104.
3. Brookes C, Shand K, Jones WR. A reevaluation of the ferning test to detect ruptured membranes. Aust N Z J Obstet Gynaecol. 1986;26:260-264.
4. Reece EA, Chervenak FA, Moya FR, et al. Amniotic fluid arborization: effect of blood, meconium, and pH alterations. Obstet Gynecol. 1984;64:248-250.
5. Rosemond RL, Lombardi SJ, Boehm FH. Ferning of amniotic fluid contaminated with blood. Obstet Gyncol. 1990;75:338-340.
6. McGregor JA, Johnson S. “Fig leaf” ferning and positive nitrazine testing: semen as a cause of misdiagnosis of premature rupture of membranes. Am J Obstet Gynecol. 1985;151:1142-1143.
7. Lodeiro JG, Hsieh KA, Byers JH, et al. The fingerprint, a false-positive fern test. Obstet Gynecol. 1989;73:873-874.
8. American College of Obstetricians and Gynecologists. Premature rupture of membranes. ACOG Practice Bulletin No. 80. Obstet Gynecol. 2007;109:1007-1019.
1. De Haan HH, Offermans PM, Smits F, et al. Value of the fern test to confirm or reject the diagnosis of ruptured membranes is modest in nonlaboring women presenting with nonspecific vaginal fluid loss. Am J Perinatol. 1994;11:46-50.
2. Bennett SL, Cullen JB, Sherer DM, et al. The ferning and nitrazine tests of amniotic fluid between 12 and 41 weeks gestation. Am J Perinatol. 1993;10:101-104.
3. Brookes C, Shand K, Jones WR. A reevaluation of the ferning test to detect ruptured membranes. Aust N Z J Obstet Gynaecol. 1986;26:260-264.
4. Reece EA, Chervenak FA, Moya FR, et al. Amniotic fluid arborization: effect of blood, meconium, and pH alterations. Obstet Gynecol. 1984;64:248-250.
5. Rosemond RL, Lombardi SJ, Boehm FH. Ferning of amniotic fluid contaminated with blood. Obstet Gyncol. 1990;75:338-340.
6. McGregor JA, Johnson S. “Fig leaf” ferning and positive nitrazine testing: semen as a cause of misdiagnosis of premature rupture of membranes. Am J Obstet Gynecol. 1985;151:1142-1143.
7. Lodeiro JG, Hsieh KA, Byers JH, et al. The fingerprint, a false-positive fern test. Obstet Gynecol. 1989;73:873-874.
8. American College of Obstetricians and Gynecologists. Premature rupture of membranes. ACOG Practice Bulletin No. 80. Obstet Gynecol. 2007;109:1007-1019.
Evidence-based answers from the Family Physicians Inquiries Network
How can we minimize recurrent ankle sprains?
USING EXTERNAL ANKLE SUPPORTS during physical activity significantly reduces the likelihood of primary and secondary sprains (strength of recommendation [SOR]: A, systematic review).
Proprioception rehabilitation substantially decreases further injury after an ankle sprain (SOR: A, 3 randomized control trials [RCTs] and 1 prospective cohort study).
Evidence summary
A Cochrane review of 14 randomized and quasi-randomized trials concluded that patients who used external ankle supports, such as semi-rigid orthotics or air cast braces, suffered significantly fewer ankle sprains than controls (relative risk [RR]=0.53; 95% confidence interval [CI], 0.40-0.69; number needed to treat [NNT]=22).1 Participants in the trials ranged in age from adolescence to middle age and were either at risk of injury or had suffered a previous ligament injury.
The benefits of ankle supports were most apparent in patients with previous injuries but still evident in patients who hadn’t been injured. External ankle support is recommended for sports with a high risk of ankle injury, such as soccer and basketball, but the decision to use it should be based on perceived risk of injury as opposed to perceived loss of performance.1
Research is insufficient to support wearing high-top shoes to prevent primary and secondary ankle sprains.
Also helpful: Balance and proprioceptive training
A systematic review of 2 RCTs with 703 and 1057 patients concluded that completing a minimum of 6 weeks of balance and coordination training after an acute injury substantially reduced the risk of recurrent ankle sprains for as long as a year (NNT=22; absolute risk reduction=4.5%).2
Proprioceptive training appears to effectively prevent primary and secondary ankle injuries but is more beneficial for patients with a previous ankle injury. A recent RCT that enrolled 522 active sports participants with recent ankle injuries found that those who completed an 8-week, self-guided, proprioceptive training program suffered significantly fewer recurrent sprains at 1 year than the control group (22% vs 33%; relative risk reduction=35%; NNT=9).3
Recommendations
The American Orthopaedic Society for Sports Medicine continues to endorse rest, ice, compression, and elevation for optimal initial care of ankle sprains.4 The American College of Sports Medicine suggests that rehabilitation after an ankle injury should include guided stretching and strengthening of the ankle joint as well as balance training to prevent future injuries.5 Both groups also recommend external ankle supports instead of taping to prevent ankle reinjury.4,5
1. Handoll HH, Rowe BH, Quinn KM, et al. Interventions for preventing ankle ligament injuries. Cochrane Database Syst Rev. 2009;(3):CD000018.-
2. Patrick OM, Hertel J. Systematic review of postural control and lateral ankle instability, part II: is balance training clinically effective? J Athletic Trng. 2008;43:305-315.
3. Hupperets MW, Verhagen EA, VanMechelen W. Effect of unsupervised home based proprioceptive training on recurrences of ankle sprain: randomised control trial. Available at: www.bmj.com/cgi/content/full/339/jul09_1/b2684?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=hupperets&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT. Accessed July 29, 2010.
4. American Orthopaedic Society for Sports Medicine. Ankle sprains: how to speed your recovery. Available at: http://www.evanekman.com/pdfs/3ST%20Ankle%20Sprains%2008.pdf. Accessed October 10, 2011.
5. American College of Sports Medicine. Current comment: ankle sprains and the athlete. Available at: http://www.acsm.org/docs/current-comments/anklesprainstemp.pdf. Accessed on October 10, 2011.
USING EXTERNAL ANKLE SUPPORTS during physical activity significantly reduces the likelihood of primary and secondary sprains (strength of recommendation [SOR]: A, systematic review).
Proprioception rehabilitation substantially decreases further injury after an ankle sprain (SOR: A, 3 randomized control trials [RCTs] and 1 prospective cohort study).
Evidence summary
A Cochrane review of 14 randomized and quasi-randomized trials concluded that patients who used external ankle supports, such as semi-rigid orthotics or air cast braces, suffered significantly fewer ankle sprains than controls (relative risk [RR]=0.53; 95% confidence interval [CI], 0.40-0.69; number needed to treat [NNT]=22).1 Participants in the trials ranged in age from adolescence to middle age and were either at risk of injury or had suffered a previous ligament injury.
The benefits of ankle supports were most apparent in patients with previous injuries but still evident in patients who hadn’t been injured. External ankle support is recommended for sports with a high risk of ankle injury, such as soccer and basketball, but the decision to use it should be based on perceived risk of injury as opposed to perceived loss of performance.1
Research is insufficient to support wearing high-top shoes to prevent primary and secondary ankle sprains.
Also helpful: Balance and proprioceptive training
A systematic review of 2 RCTs with 703 and 1057 patients concluded that completing a minimum of 6 weeks of balance and coordination training after an acute injury substantially reduced the risk of recurrent ankle sprains for as long as a year (NNT=22; absolute risk reduction=4.5%).2
Proprioceptive training appears to effectively prevent primary and secondary ankle injuries but is more beneficial for patients with a previous ankle injury. A recent RCT that enrolled 522 active sports participants with recent ankle injuries found that those who completed an 8-week, self-guided, proprioceptive training program suffered significantly fewer recurrent sprains at 1 year than the control group (22% vs 33%; relative risk reduction=35%; NNT=9).3
Recommendations
The American Orthopaedic Society for Sports Medicine continues to endorse rest, ice, compression, and elevation for optimal initial care of ankle sprains.4 The American College of Sports Medicine suggests that rehabilitation after an ankle injury should include guided stretching and strengthening of the ankle joint as well as balance training to prevent future injuries.5 Both groups also recommend external ankle supports instead of taping to prevent ankle reinjury.4,5
USING EXTERNAL ANKLE SUPPORTS during physical activity significantly reduces the likelihood of primary and secondary sprains (strength of recommendation [SOR]: A, systematic review).
Proprioception rehabilitation substantially decreases further injury after an ankle sprain (SOR: A, 3 randomized control trials [RCTs] and 1 prospective cohort study).
Evidence summary
A Cochrane review of 14 randomized and quasi-randomized trials concluded that patients who used external ankle supports, such as semi-rigid orthotics or air cast braces, suffered significantly fewer ankle sprains than controls (relative risk [RR]=0.53; 95% confidence interval [CI], 0.40-0.69; number needed to treat [NNT]=22).1 Participants in the trials ranged in age from adolescence to middle age and were either at risk of injury or had suffered a previous ligament injury.
The benefits of ankle supports were most apparent in patients with previous injuries but still evident in patients who hadn’t been injured. External ankle support is recommended for sports with a high risk of ankle injury, such as soccer and basketball, but the decision to use it should be based on perceived risk of injury as opposed to perceived loss of performance.1
Research is insufficient to support wearing high-top shoes to prevent primary and secondary ankle sprains.
Also helpful: Balance and proprioceptive training
A systematic review of 2 RCTs with 703 and 1057 patients concluded that completing a minimum of 6 weeks of balance and coordination training after an acute injury substantially reduced the risk of recurrent ankle sprains for as long as a year (NNT=22; absolute risk reduction=4.5%).2
Proprioceptive training appears to effectively prevent primary and secondary ankle injuries but is more beneficial for patients with a previous ankle injury. A recent RCT that enrolled 522 active sports participants with recent ankle injuries found that those who completed an 8-week, self-guided, proprioceptive training program suffered significantly fewer recurrent sprains at 1 year than the control group (22% vs 33%; relative risk reduction=35%; NNT=9).3
Recommendations
The American Orthopaedic Society for Sports Medicine continues to endorse rest, ice, compression, and elevation for optimal initial care of ankle sprains.4 The American College of Sports Medicine suggests that rehabilitation after an ankle injury should include guided stretching and strengthening of the ankle joint as well as balance training to prevent future injuries.5 Both groups also recommend external ankle supports instead of taping to prevent ankle reinjury.4,5
1. Handoll HH, Rowe BH, Quinn KM, et al. Interventions for preventing ankle ligament injuries. Cochrane Database Syst Rev. 2009;(3):CD000018.-
2. Patrick OM, Hertel J. Systematic review of postural control and lateral ankle instability, part II: is balance training clinically effective? J Athletic Trng. 2008;43:305-315.
3. Hupperets MW, Verhagen EA, VanMechelen W. Effect of unsupervised home based proprioceptive training on recurrences of ankle sprain: randomised control trial. Available at: www.bmj.com/cgi/content/full/339/jul09_1/b2684?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=hupperets&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT. Accessed July 29, 2010.
4. American Orthopaedic Society for Sports Medicine. Ankle sprains: how to speed your recovery. Available at: http://www.evanekman.com/pdfs/3ST%20Ankle%20Sprains%2008.pdf. Accessed October 10, 2011.
5. American College of Sports Medicine. Current comment: ankle sprains and the athlete. Available at: http://www.acsm.org/docs/current-comments/anklesprainstemp.pdf. Accessed on October 10, 2011.
1. Handoll HH, Rowe BH, Quinn KM, et al. Interventions for preventing ankle ligament injuries. Cochrane Database Syst Rev. 2009;(3):CD000018.-
2. Patrick OM, Hertel J. Systematic review of postural control and lateral ankle instability, part II: is balance training clinically effective? J Athletic Trng. 2008;43:305-315.
3. Hupperets MW, Verhagen EA, VanMechelen W. Effect of unsupervised home based proprioceptive training on recurrences of ankle sprain: randomised control trial. Available at: www.bmj.com/cgi/content/full/339/jul09_1/b2684?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=hupperets&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT. Accessed July 29, 2010.
4. American Orthopaedic Society for Sports Medicine. Ankle sprains: how to speed your recovery. Available at: http://www.evanekman.com/pdfs/3ST%20Ankle%20Sprains%2008.pdf. Accessed October 10, 2011.
5. American College of Sports Medicine. Current comment: ankle sprains and the athlete. Available at: http://www.acsm.org/docs/current-comments/anklesprainstemp.pdf. Accessed on October 10, 2011.
Evidence-based answers from the Family Physicians Inquiries Network