Amniotic fluid is a mixture of:
- Fluid from the fetal lung.
- Cellular debris from the skin
(and its glands), the lung, kidney, transitional epithelium from the fetal
- Meconium from the fetal colon
may be present in late gestation.
ECHOGENIC AMNIOTIC FLUID PRIOR TO 24 WEEKS
ECHOGENIC AMNIOTIC FLUID AFTER 24 WEEKS
- Cellular debris (vernix
caseosa) - the amount of cellular debris may be considerable and may
render the amniotic fluid opaque to the ultrasound beam. This cellular
debris is most apparent immediately after fetal movement when it may be
seen to swirl around and then settle once again to the dependent portion
of the uterus (1). There is a vague relationship between the amount of
cellular debris and fetal maturity.
In a recent study (2) the causes of third trimester echogenic fluid was:
- Vernix (95%).
- Meconium (5%).
It has been suggested that layering of echoes may be a sign
of meconium as opposed to vernix (3), however this is an unreliable sign (2).
The layering effect has been reported with vernix (4), and evenly distributed
particles have been described with meconium (5).
- Manning FA (ed). Fetal
medicine. Principles and practice. Appleton and Lange, Norwalk,
- Brown DL, Polger M, Clark PK
et.al. Very echogenic amniotic fluid: Ultrasonography-amniocentesis correlation.
J Ultrasound Med 1994;13:95-97.
- Benacerraf BR, Gatter MA,
Ginsburgh F. Ultrasonographic diagnosis of meconium-stained amniotic
fluid. Obstet Gynecol 1984;149:570.
- Sepulveda WH, Quiroz VH.
Sonographic detection of echogenic amniotic fluid and its clinical
significance. J Perinat Med 1989;17:333.
- Sherer DM, Abramowicz JS,
Smith JA et.al. Sonographically homogeneous echogenic amniotic fluid in
detecting meconium-stained amniotic fluid. Obstet Gynecol 1991;78:819.