Learning Objectives• Character of A.F• Functions of A.F• Oligo-Poly-Hydramnios Definition Etiology Diagnosis Treatment
The Fetal MembranesDefinition: Fetal membranes are all the structures that develop from thezygote and do not share in the formation of the embryo(extraembryonic structures from the primitive blastomeres).Fetal membranes are:a. Chorion.b. Amnion.c. Yolk sac.d. The umbilical cord including allantois and body stalk.
Amnion & Amniotic cavity- It is a membrane which bounds the amnioticcavity.- It is continuous with the ectoderm of the embryo.- It contains about 800-1000 ml of watery and clearfluid at full term.
Amniotic FluidThe amniotic fluid is that fluid surrounding the developing fetus that is found within the amniotic sac contained in the mothers womb.• Physical characteristics ; - It is clear pale yellow fluid.- pH of is around 7.2.- Specific gravity of 1.0069 – 1.008.--
Composition of amniotic fluid - 98% water, 2% solid substances like inorganic & organic salts, fetal epithelium, protein & enzymes.Origin: The following forms the amniotic fluid: 1- Amniotic membrane 2- Maternal tissue (interstitial) fluid by diffusion across the amnio-chorionic membrane from the deciduas parietalis. 3- Filtrated from maternal blood. 4- Fluid is also secreted by the fetal respiratory tract (300 – 400 ml daily) and enters the amniotic cavity. 5-Fetal urine.
Circulation- The amniotic fluid, formed by amniotic membrane & filtrated from maternal blood accumulates in the amniotic cavity,- Then, it is swallowed by the embryo.- Lastly, it passes as fetal urine to accumulate again in the amniotic cavity.Volume of the amniotic fluid:The volume of amniotic fluid increases slowly from 30 ml at 10 weeks gestation to 350 ml at 20 weeks to 700 – 1000 ml by 37 weeks.
FunctionBefore labour:1-It forms an isolating bag around the embryo protecting him from external trauma, shock & temperature.2-It prevents adhesion of the embryo to its membranes.3-It allows homogenous media needed for the growth of the embryo.4-It permits the free movement of the embryo needed for muscular exercise.
FunctionDuring labor: 1- It forms the bags of fore water and hind water. 2-The bag of fore water allows regular dilatation of the cervix. 3-After rupture of membrane the amniotic fluid serves as a lubricant for fetus descent. 4-Also the amniotic fluid is bacteriostatic.
Clinical importance of AF:• Screening for fetal malformation (serum α-fetoprotien).• Assessment of fetal well-being (amniotic fluid index).• Assessment of fetal lung maturity (L/S ratio).• Diagnosis and follow up of labor.• Diagnosis of PROM (ferning test).• Diagnosis of fetal chromosomal abnormalities ( Downsyndrome, Edward syndrome, and others), and for DNA studies fordiagnosis of some single gene disorders.
Summary of the routine chemical tests performed on amniotic fluid• Tests for the Well-being and Maturity• __________________________________________________________• Test Normal values at term Significance• __________________________________________________________• Bilirubin scan 0.025 mg/dl Hemolytic disease of the newborn• L/S ratio 2.0 Fetal lung maturity• Phosphatidyl- Present Fetal lung maturityGlycerol• Creatinine 1.3 – 4.0 mg/dl Fetal age• Alpha fetal protein 4.0 mg/dl Neural tube disorders• __________________________________________________________ 12
Amniotic fluid volume assessment• Clinical assessment is unreliable.• Objective assessment depends on U/S to measure: - Deepest vertical pool (DVP). - Amniotic fluid index (AFI). It is a total of the DVPs in each four quadrants of the uterus. it is a more sensitive indicator of AFV throughout pregnancy.
Amniotic fluid abnormalities Oligohydramnios: Defined as reduced amniotic fluid i.e. amniotic fluid index of 5 cm or less or the deepest vertical pool < 2 cm. Polyhydramnios: Defined as excessive amount of amniotic fluid of 2000 ml or more AFI of > 25 cm or the deepest vertical pool of > 8 cm) .
Etiology of Polyhydramnios: Fetal Anomalies• Problems with swallowing and GI absorption• Increased transudation of fluid: anencephaly, spina bifida• Increased urination: anencephaly (lack of ADH, stimulation of urination centers)• Decreased inspiration
TREATMENT• Mild to Moderate hydramnios: rarely requires treatment• Hospitalization, bed rest• Amniocentesis: to relieve maternal distress and to test for fetal lung maturity. Complications: ruptured membrane, chorioamnionitis, placental abruption, preterm labour• Non-steroidal anti-inflammatory analgesia• Blood sugar control
management• Indomethacin therapy: . - impairs lung liquid production/enhances absorption. - ↓fluid movement across fetal membranes. * complications: premature closure of ductus arteriosus, impairment of renal function, and cerebral vasoconstriction. So not used after 34 weeks
TREATMENT ACC. TO CAUSE• Drug induced – OMIT DRUG• PROM – INDUCTION• PPROM – Antibiotics,steroid – Induction• FETAL SURGERY VESICO AMNIOTIC SHUNT-PUV Laser photocoagulation for TTTS 36
Amniocentesis• Amniocentesis is the removal of a small amount of amniotic fluid from the sac around the baby.• This is usually performed at 16 weeks in pregnancy.• A fine needle is inserted under ultrasound guidance through the mothers abdomen into a pool of amniotic fluid.
AmniocentesisStudies of the cells obtained from the amniotic fluid permit:1- Chromosomal analysis of the cells which can be performed to investigate the following; Diagnosis of sex of the fetus Detection of chromosomal abnormalities e.g. trisomy 21 (Down’s syndrome) DNA studies2- The cells may indicate genetically transmitted diseases( Inherited disorders e.g Cystic Fibrosis).3-To check for developmental problems e.g. Spina Bifida .4- Other studies can be done directly on the amniotic fluid including measurement of alpha-fetoprotein where high levels of alpha-fetoproteins in the amniotic fluid indicate the presence of a severe neural tube defect whereas low levels of alpha- fetoproteins may indicate chromosomal abnormalities .
AmniocentesisWho is the proper candidate for an Amniocentesis investigation?1-Those whom are suspected to have possible problems indicated by certain tests conducted previously,(e.g If pregnancy is complicated by a condition such as Rh-incombatibility,the doctor can use amniocentesis to find out if the babys lungs are developed enough to endure an early delivery).2- Family history of genetic abnormalities (in this case would be advisable to seek genetic counseling before becoming pregnant)3-Those that have been exposed to certain risk enviromental factors that might lead to fetal abnormalities .
AmniocentesisWhat are the risks of amniocentesis?• - Abortion: about 1 in 200 to 400 women aborted (higher risk if done in the first quarter)• - Uterine infection: 1 in 1000