Is amniotic fluid material in the central circulation of peripartum patients pathologic?

Cytologic findings of amniotic fluid material (AFM) in pulmonary arterial blood (PAB) of survivors of amniotic fluid embolism (AFE) are assumed to be pathologic. However, no cytologic studies of central blood from patients without clinical AFE have been reported. To address this question PAB samples from peripartum patients without clinical AFE were examined for the presence and extent of AFM (including squames, mucin, and lanugo hair). Ten samples were obtained from five patients. All patients had at least one sample postpartum. Peripheral blood from a nonpregnant adult female control was processed similarly. Results were compared to a PAB sample from a patient with clinical AFE. The patient with clinical AFE had many squames, clumps of lanugo hair, and mucin in one sample. In six of ten study samples, there were squames, accompanied in two cases by lanugo hair or trophoblast. In nine of ten samples there was mucin. There appeared to be no difference in cytologic findings in patients according to mode of delivery or sampling time. The control blood sample was negative for amniotic fluid-like material. AFM may be found in peripartum patients without clinical amniotic fluid embolism. A quantitative difference was seen between the index patient and each of our five study patients. These findings suggest that there is a quantitative continuum of AFM transported to the central circulation in peripartum patients which may, in part, explain the varied clinical presentations and severity of AFE.