Second trimester amniotic fluid is reliably fern positive and α₁-microglobulin positive: Dispelling a labor deck myth

Objective Many physicians erroneously believe and have propagated the myth that a second trimester amniotic fluid sample will not fern. We attempted to redemonstrate ferning and to demonstrate the efficacy of an assay for α₁-microglobulin in second trimester amniotic fluid samples. Study Design Amniotic fluid samples were collected from women undergoing routine genetic amniocentesis between 15 and 26 weeks. A total of 97 samples of second trimester amniotic fluid were placed on slides and examined for ferning at 5 and 10 minutes. An α₁-microglobulin assay was performed on each sample. Data were recorded and reported. Results Approximately 93% of samples were fern positive at 5 minutes and 100% were fern positive at 10 minutes. All samples were α₁-microglobulin positive. Conclusion Pure amniotic fluid is reliably fern and α₁-microglobulin positive in the second trimester. Republication of data only available in pre-online sources will benefit physicians and patients.