Amniotic fluid sludge (ultrasound)

Last revised by Arlene Campos on 31 Jan 2024

Amniotic fluid sludge is a finding in obstetric transvaginal ultrasound scanning. Defined as free-floating hyperechogenic material in close proximity to the cervical internal os within the amniotic cavity of women with intact fetal membranes 1. It images as a dense, homogenous mass 2.

Amniotic fluid sludge represents a collection of bacterial and inflammatory cells embedded in an amorphous material consistent with microbial biofilm 3. On aspiration, amniotic fluid sludge is usually cloudy and thick with an elevated white cell count and may be due to a microbial invasion of the amniotic cavity 1.

Amniotic fluid sludge has been identified as a potential marker of adverse pregnancy and perinatal outcomes. Amniotic fluid sludge is associated with spontaneous pre-term labor and, therefore, lower gestational age at birth, lower neonatal birthweight, and increased neonatal intensive care unit admission rate and neonatal death 4.

It is also usually associated with a shortened cervical length; when the patient presents with both aspects, the pre-term labor risk increases 5.

It is proposed that amniotic fluid sludge is an indicator of intra-amniotic microbial invasion correlating with histological chorioamnionitis and funisitis 6.

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Cases and figures

  • Case 1: amniotic fluid sludge
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