Second Trimester Amniotic Fluid Is Reliably Fern Positive and α₁-Microglobulin Positive: Dispelling a Labor Deck Myth

Abstract

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.

Keywords

amniotic fluid - ruptured membranes - α₁-microglobulin - ferning

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