Presentation on theme: "AMNIOTIC FLUID. Reasons for testing - To allow antenatal diagnosis of genetic and congenital disorders (15 to 18 weeks) and later in pregnancy (20 to."— Presentation transcript:
Reasons for testing - To allow antenatal diagnosis of genetic and congenital disorders (15 to 18 weeks) and later in pregnancy (20 to 42 weeks) - To assess fetal pulmonary maturity - To assess degree of fetal distress - HDN - Anomalies: UTI, neural tube, intestinal, etc. - Fetal Infections: bacterial, viral, etc.
Physiology and composition - Liquid medium that bathes the fetus throughout its gestation - AMNION/amniotic sac – single layer of cuboidal EC
Functions of test :- Plays a role in various biochemical processes 4 Disease marker 1 Protects the fetus 2 Enables fetal movement 3 4
Formation 1- Initially produced by placenta & amnion 2- Composition is similar to dialysate of plasma 3- As gestation progresses, fetus plays more of an active role in its composition
Formation 4. Early in gestation, before skin keratinization 5. Through fetal respiration 6. Latter stages of pregnancy: major constituents come from fetal swallowing & urination 7. Exchange between Amniotic fluid & maternal plasma comes into completion every 2 to 3 hours
volume - Increases steadily throughout pregnancy - 25 to 50 ml at 12 weeks’ gestation Max vol = 1100 to 1500 ml at 36 wks’ gestation - Abnormally decreased (oligohydramnios): Congenital malformation & other conditions (e.g. premature rupture of the membranes) - Abnormally increased (hydramnios): Associated w/ decreased fetal swallowing in congenital malformations
Specimen collection - Timing After 14 wks (depending on purpose) Indications Genetic studies (bet 15 & 18) - To assess health status of fetus (later in preg) in cases of Rh isoimmunization, toxemia & DM - Maturity of fetal pulmonary system
Specimen collection Volume: 10 to 20 ml Containers: plastic, why not glass? Cover with aluminum if not colored, why? Transport & storage: ASAP Refrigerate after centrifugation for 5-15 min (24 hours)) Freezing (if storage >24 hrs)
Physical examination COLOR Colorless or very pale yellow Distinct yellow or amber – Bilirubin Green – meconium Pinkish to red – blood (e.g. HDN) Brown – severe hemolysis TURBIDITY Slightly turbid due to (fetal cells, hair and secretions
Chemical examination - Fern test The Fern Test, used in conjunction with the Nitrazine test, detects the leakage of amniotic fluid from the membranes surrounding the fetus during pregnancy. This phenomenon is in part due to the fluid’s protein and sodium chloride content. A positive test shows the presence of fern-like patterns characteristic of amniotic fluid crystals. The risk may be eliminated by the induction of labor.
Negative for crystal fern
Positive for crystal fern
Chemical examination - FETAL LUNG MATURITY TESTS Lecithin–sphingomyelin ratio Lecithin: major pulmonary surfactant L/S ratio starts out as 1.0, S eventually decreases and L increases <2.0 = fetal lung immaturity - Phosphatidyl glycerol/PG Detectable only in mature fetus
Chemical examination - Kleihauer–Betke test Staining technique to identify the presence of maternal or fetal red bloods in amniotic fluid
Reference Value 7-7.5PH Colorless to pale yellowColor ClearAppearance Less than 2.0 * MoM = Multiples of the median. α 1 -Fetoprotein AbsentAcetylcholinesterase 1.8–4.0 mg/dL at termCreatinine Less than mg/dL at term Bilirubin Greater than 2:1 at termL/S ratio Present at termPhosphatidylglycerol Normal karyotypeChromosome analysis None seenWhite blood cell count NegativeLeukocyte esterase