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Amniotic fluid


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Amniotic fluid

  1. 1. AMNIOTIC FLUID By La Lura White MD Maternal Fetal Medicine
  2. 2. AMNIOTIC FLUID <ul><li>The amniotic fluid that bathes the fetus is necessary for its proper growth and development. </li></ul><ul><li>It cushions the fetus from physical trauma </li></ul><ul><li>Provides a barrier against infection </li></ul><ul><li>Allowing for freedom of fetal movement and permitting symmetrical musculoskeletal development </li></ul><ul><li>Maintaining a relatively constant temperature for the environment surrounding the fetus, thus protecting the fetus from heat loss </li></ul><ul><li>Permitting proper lung development </li></ul>
  3. 3. AMNIOTIC FLUID <ul><li>Cleavage of zygote </li></ul><ul><li>Zygote begins cleavage in the fallopian tube </li></ul><ul><li>s/p 3 days in the fallopian tube, the morula enters uterine cavity </li></ul><ul><li>After 3 days floating in the uterine cavity it will implant </li></ul><ul><li>Gradual accumulation of fluid between blastomeres within the morula results in the formation of the blastocyst </li></ul><ul><li>Inner cell mass-embryo </li></ul><ul><li>Outer cell mass-trophoblast </li></ul>
  4. 4. AMNIOTIC FLUID <ul><li>7 1/2 days: </li></ul><ul><li>Trophoblast </li></ul><ul><li>Cytotrophoblast: individual, pale staining cells </li></ul><ul><li>Syncytiotrophoblast: dark staining nuclei within an amorphous common cytoplasm </li></ul><ul><li>Inner cell mass: embryonic disc thick ectoderm and underlying endoderm </li></ul><ul><li>Between the embryonic disc and the trophoblast, small cells appear that enclose a space that will become the amniotic cavity </li></ul>
  7. 7. AMNIOTIC FLUID <ul><li>Small cells line the inner surface of the trophoblast called amniogenic cells, later to become amniotic epithelium </li></ul><ul><li>The amnion develops by the 7-8 th day </li></ul><ul><li>Derived from fetal ectoderm </li></ul><ul><li>As the amnion enlarges, it gradually engulfs the embryo which prolapses into its cavity </li></ul><ul><li>Distention of the amniotic sac brings it in contact with the chorion laeve </li></ul><ul><li>The chorion and amnion are juxtaposed but not connected </li></ul>
  9. 9. AMNIOTIC FLUID <ul><li>Clear fluid collects within the amniotic cavity and increases with gestational age. Normal amniotic fluid levels vary. </li></ul><ul><li>50 ml 12 weeks </li></ul><ul><li>400 ml midpregnancy </li></ul><ul><li>800 ml 34 weeks </li></ul><ul><li>1000ml 36-38 weeks </li></ul><ul><li>At full term, there is between 500-1000 cc of amniotic fluid. </li></ul>
  12. 12. AMNIOTIC FLUID <ul><li>Composition and volume of amniotic fluid changes as pregnancy advances </li></ul><ul><li>In the first half of pregnancy, the fluid is the same as the extracellular fluid of the fetus, devoid of particulate matter </li></ul><ul><li>Produced by amniotic membranes </li></ul><ul><li>Fluid also passes across fetal skin </li></ul>
  13. 13. AMNIOTIC FLUID <ul><li>By the fourth month, the fetus contributes to amniotic fluid via: </li></ul><ul><li>urinating </li></ul><ul><li>swallowing </li></ul><ul><li>movement of fluid in and out of the respiratory tract </li></ul><ul><li>Fetal urination will eventually comprise the majority of the amniotic fluid </li></ul>
  14. 14. AMNIOTIC FLUID <ul><li>The fetal kidneys start to develop during the 4th and 5th weeks of gestation and begin to excrete urine into the amniotic fluid at the 8th to 11th week </li></ul><ul><li>At the 20th week the fetal kidneys produce most of the amniotic fluid </li></ul><ul><li>Fetal urine is hypotonic (c/w plasma) because of lower electrolyte concentration </li></ul><ul><li>Contains more urea, creatinine and uric acid </li></ul><ul><li>Osmolality decrease with increasing gestational age </li></ul>
  15. 15. AMNIOTIC FLUID <ul><li>An important function of the fetal kidney is to maintain a urine output sufficient to maintain amniotic fluid volume </li></ul><ul><li>Daily urine production is approximately 30% of fetal weight </li></ul><ul><li>The excreted urine does not serve real excretory or homeostatic function because the urine, via the amniotic fluid , is recycled back to the fetus by swallowing (25% of fetal weight) </li></ul>
  16. 16. AMNIOTIC FLUID <ul><li>The factors involved in regulating amniotic fluid volume are still not completely understood. The 6 proposed pathways (Brace, 1997) for fluid movement into and out of the amniotic cavity include: </li></ul>
  17. 17. AMNIOTIC FLUID <ul><li>Pathway Volume (ml)/day </li></ul><ul><li>to the fetus to amniotic fluid </li></ul><ul><li>Fetal swallowing 500-1000 </li></ul><ul><li>Oral secretions 25 </li></ul><ul><li>Secretions from the </li></ul><ul><li>respiratory tract 170 170 </li></ul><ul><li>Fetal urination 800-1200 </li></ul><ul><li>Intramembranous flow </li></ul><ul><li>across the placenta, </li></ul><ul><li>umbilical cord 200-500 </li></ul><ul><li>Transmembraneous flow </li></ul><ul><li>from the amniotic cavity into </li></ul><ul><li>the uterine circulation 10 </li></ul>
  18. 18. AMNIOTIC FLUID <ul><li>Glycerophospholipids (lecithin, sphingomyelin) from the lungs accumulate in AF </li></ul><ul><li>Desquamated fetal cells, lanugo, scalp hair and vernix caseosa are shed </li></ul><ul><li>Also contains albumin, urea, uric acid, creatinine,, bilirubin, fat, fructose, leukocytes, proteins, epithelial cells, enzymes </li></ul>
  19. 19. AMNIOTIC FLUID <ul><li>Amniotic fluid volume (AFI) </li></ul><ul><ul><li>The volume of the amniotic fluid is evaluated by visually dividing the mother's abdomen into 4 quadrants </li></ul></ul><ul><ul><li>The largest vertical pocket of fluid in each quadrant is measured in centimeters </li></ul></ul><ul><ul><li>Cord containing pocket < 30% </li></ul></ul><ul><ul><li>The total volume is calculated by adding these values </li></ul></ul><ul><ul><li><5 oligohydramnios </li></ul></ul>
  20. 20. AMNIOTIC FLUID <ul><li>The 2 cm x 2 cm pocket definition (Magann, 1999a) and an AFI < 5 cm (Horsager, 1994) were compared to the actual amniotic fluid volume as measured by a dye-dilution technique. </li></ul><ul><li>The single 2 cm pocket had a sensitivity of 9.5% </li></ul><ul><li>AFI < 5.0 cm had a sensitivity of 18% for the detection of oligohydramnios </li></ul>
  21. 21. AMNIOTIC FLUID <ul><ul><li>6-8 borderline AFI </li></ul></ul><ul><ul><li>8-24 normal </li></ul></ul><ul><ul><li>>24 polyhydramnios </li></ul></ul>
  22. 22. AMNIOTIC FLUID Oligohydramnios Normal
  23. 23. AMNIOTIC FLUID <ul><li>Polyhydramnios is usually defined as; </li></ul><ul><li>Amniotic fluid index (AFI) more than 24 cm </li></ul><ul><li>Single pocket of fluid at least 8 cm in deep that results in more than 2000 mL of fluid </li></ul><ul><li>Occurs in 1% of pregnancies </li></ul><ul><li>Preterm labor and delivery occurs in approximately 26% of mothers with polyhydramnios. </li></ul><ul><li>Other complications are premature rupture of the membranes (PROM), abruptio placenta, malpresentation, cesarean delivery, and postpartum hemorrhage </li></ul>
  24. 24. AMNIOTIC FLUID <ul><li>An abnormally high level of amniotic fluid, polyhydramnios, alerts the clinician to possible fetal anomalies </li></ul><ul><li>80-90% are idiopathic </li></ul><ul><li>In pregnancies affected by polyhydramnios, approximately 20% of the neonates are born with a congenital anomaly of some type </li></ul><ul><li>Gastrointestinal system (40%), central nervous system (26%), cardiovascular system (22%), genitourinary system (13%) and 50% of the patients had no associated risk factors. </li></ul>
  25. 25. AMNIOTIC FLUID <ul><li>Fetal akinesia syndrome: Absence of swallowing </li></ul><ul><li>Blockage of the fetus' gastrointestinal tract </li></ul><ul><li>Esophageal atresia (usually associated with a tracheoesophageal fistula) </li></ul><ul><li>Tracheal agenesis </li></ul><ul><li>Duodenal atresia </li></ul><ul><li>. </li></ul>
  26. 26. AMNIOTIC FLUID <ul><ul><li>Non-genetic </li></ul></ul><ul><ul><li>Congenital cardiac-rhythm anomalies associated with hydrops, fetal-to-maternal hemorrhage, and parvovirus infection </li></ul></ul><ul><ul><li>Maternal type 2 diabetes mellitus </li></ul></ul><ul><ul><li>Multiple gestations </li></ul></ul>
  27. 27. AMNIOTIC FLUID <ul><li>Polyhydramnios: treatment </li></ul><ul><ul><li>Patients with polyhydramnios tend to have a higher incidence of preterm labor secondary to overdistention of the uterus. </li></ul></ul><ul><ul><li>Schedule weekly or twice weekly perinatal visits and cervical examinations. </li></ul></ul><ul><ul><li>Place patients on bed rest to decrease the likelihood of preterm labor. </li></ul></ul><ul><ul><li>Perform serial ultrasonography to determine the AFI and document fetal growth. </li></ul></ul>
  28. 28. AMNIOTIC FLUID <ul><li>Polyhydramnios </li></ul><ul><li>Treat underlying cause </li></ul><ul><li>Fetal anemia: Fetal transfusion </li></ul><ul><li>Diabetes: control blood sugar </li></ul><ul><li>Twin-Twin Transfusion: ablation </li></ul>
  29. 29. AMNIOTIC FLUID <ul><li>Polyhydramnios: Treatment </li></ul><ul><li>Procedures: </li></ul><ul><ul><li>Reductive amniocentesis may be performed and has contributed to prolonged pregnancy in patients who are severely affected by hydramnios. </li></ul></ul><ul><ul><li>This procedure can reduce the risk of preterm labor, PROM, umbilical cord prolapse, and placental abruption. </li></ul></ul><ul><ul><li>However, if too much fluid is removed, the risk of placental abruption due to uterine compression increases. </li></ul></ul><ul><ul><li>Other risks of the procedure include infection, bleeding, and trauma to the fetus. </li></ul></ul><ul><ul><li>Laser ablation of placental vessels may be efficacious in cases of fetal-fetal transfusion syndrome </li></ul></ul>
  30. 30. AMNIOTIC FLUID <ul><li>Most cases of polyhydramnios respond in the first week of treatment with indomethacin </li></ul><ul><li>The approach appears to be highly effective (90-100% in some studies), provided that the cause is not hydrocephalus or a neuromuscular disorder that alter fetal swallowing. </li></ul><ul><li>Drug Category: Prostaglandin inhibitors -- When administered to pregnant women with polyhydramnios, these drugs can reduce fetal urinary flow, decreasing the volume of amniotic fluid. </li></ul><ul><li>Drug Name </li></ul><ul><li>Indomethacin (Indocin) -- Rapidly absorbed; metabolism occurs in liver by demethylation, deacetylation, and glucuronide conjugation </li></ul><ul><li>Inhibits prostaglandin synthesis. </li></ul><ul><li>Adult Dose 25 mg PO q6h </li></ul>
  31. 31. AMNIOTIC FLUID <ul><li>Contraindications </li></ul><ul><li>Documented hypersensitivity; GI bleeding; renal insufficiency </li></ul><ul><li>Interactions: </li></ul><ul><li>Co administration with aspirin increases risk of serious NSAID-related adverse effects </li></ul><ul><li>Probenecid may increase concentrations and, possibly, toxicity of NSAIDs </li></ul><ul><li>Decrease effect of hydralazine, captopril, and beta-blockers </li></ul><ul><li>Decrease diuretic effects of furosemide and thiazides </li></ul><ul><li>Monitor PT closely (instruct patients to watch for signs of bleeding) </li></ul><ul><li>Increase risk of methotrexate toxicity </li></ul><ul><li>Increase phenytoin levels when administered concurrently </li></ul>
  32. 32. AMNIOTIC FLUID <ul><li>Usually safe but benefits must outweigh the risks </li></ul><ul><li>Can cause fetal renal and CNS complications; associated with premature closure of the fetal ductus arteriosus when administered near term </li></ul><ul><li>Periventricular leukomalacia has been reported in infants whose mothers have received indomethacin as a tocolytic. </li></ul><ul><li>Acute renal insufficiency, hyperkalemia, hyponatremia, interstitial nephritis, and renal papillary necrosis may occur; increases risk of acute renal failure in patients with preexisting renal disease or compromised renal perfusion; </li></ul><ul><li>Reversible leukopenia may occur (discontinue if persistent leukopenia, granulocytopenia, or thrombocytopenia present). </li></ul>
  33. 33. AMNIOTIC FLUID <ul><li>Oligohydramnios occurs in 4% of pregnancies </li></ul><ul><li>Sonographically defined as an AFI less than 5 cm or the absence of a fluid pocket 2-3 cm in depth. </li></ul><ul><li>Inadequate levels of amniotic fluid, oligohydramnios, results in poor development of the lung tissue and can lead to fetal death secondary to bronchopulmonary dysplasia (BPD) and pulmonary hypoplasia </li></ul><ul><li>Rupture of the membranes is the most common cause of oligohydramnios and if prolonged can result in chorio </li></ul>
  34. 34. AMNIOTIC FLUID <ul><li>Oligohydramnios </li></ul><ul><ul><li>Fetal urinary tract anomalies, such as renal agenesis (Potter’s syndrome), polycystic kidneys, or any urinary obstructive lesion (eg, posterior urethral valves) </li></ul></ul><ul><ul><li>Placental insufficiency, as seen in PIH, maternal diabetes, or postmaturity syndrome when the pregnancy extends beyond 42 weeks' gestation </li></ul></ul><ul><ul><li>Maternal use of prostaglandin synthase inhibitors or angiotensin-converting enzyme (ACE) inhibitors </li></ul></ul>
  35. 35. AMNIOTIC FLUID <ul><li>Severe oligohydramnios </li></ul><ul><ul><li>Marked deformation of the fetus due to of intrauterine constraint </li></ul></ul><ul><ul><li>External compression with a flattened facies </li></ul></ul><ul><ul><li>Epicanthal folds </li></ul></ul><ul><ul><li>Hypertelorism </li></ul></ul><ul><ul><li>Low-set ears </li></ul></ul><ul><ul><li>Mongoloid slant of the palpebral fissure </li></ul></ul><ul><ul><li>Crease below the lower lip </li></ul></ul><ul><ul><li>Micrognathia </li></ul></ul><ul><ul><li>Thoracic compression </li></ul></ul><ul><ul><li>Bowed legs </li></ul></ul><ul><ul><li>Clubbed feet </li></ul></ul>
  36. 36. AMNIOTIC FLUID <ul><li>The mortality rate in oligohydramnios is high </li></ul><ul><li>Pulmonary hypoplasia </li></ul><ul><li>IUGR </li></ul><ul><li>Meconium stainin </li></ul><ul><li>Fetal heart conduction abnormalities </li></ul><ul><li>Poor tolerance of labor </li></ul><ul><li>Lower Apgar scores </li></ul><ul><li>Fetal acidosis </li></ul><ul><li>Physical deformities </li></ul>
  37. 37. AMNIOTIC FLUID <ul><li>Oligohydramnios: Treatment </li></ul><ul><li>Maternal bed rest and hydration promote the production of amniotic fluid by increasing the maternal intravascular space. </li></ul><ul><li>Bed rest may also help when PIH is present, allowing prolongation of the pregnancy. </li></ul><ul><li>Oral hydration </li></ul>
  38. 38. AMNIOTIC FLUID <ul><li>Oligohydramnios: Treatment </li></ul><ul><li>The transabdominal instillation of indigo carmine may be used to evaluate for PROM </li></ul><ul><li>The transcervical instillation of isotonic sodium chloride solution (ie, amnioinfusion) at the time of delivery reduces the risk of cord compression, fetal distress and meconium dilution. </li></ul><ul><li>It also reduces the potential need for cesarean delivery. </li></ul>
  39. 39. AMNIOTIC FLUID <ul><li>15 week fetus with posterior urethral valves. </li></ul><ul><li>The fetus is in breech presentation. The bladder (b) is massively distended. </li></ul>
  40. 40. AMNIOTIC FLUID <ul><li>15 week fetus with posterior urethral valves. </li></ul><ul><li>) Enlarged &quot;key-hole&quot; bladder associated with posterior urethral valves. </li></ul>
  41. 41. AMNIOTIC FLUID <ul><li>19 week fetus with Turner's syndrome, cystic hygroma (arrows) and oligohydramnios </li></ul>
  42. 42. AMNIOTIC FLUID <ul><li>Mortality/Morbidity: </li></ul><ul><li>Chamberlin used ultrasonography to evaluate the perinatal mortality rate (PMR) in 7562 patients with high-risk pregnancies. </li></ul><ul><li>The PMR of patients with normal fluid volumes was 1.97 deaths per 1000 patients. </li></ul><ul><li>The PMR increased to 4.12 deaths per 1000 patients with polyhydramnios </li></ul><ul><li>56.5 deaths per 1000 patients with oligohydramnios </li></ul>
  43. 43. AMNIOTIC FLUID <ul><li>Amnionitic fluid evaluation allows assessment of the fetal intrauterine environment </li></ul><ul><li>Potentially invaluable information </li></ul><ul><li>Requires close follow-up and evaluation </li></ul><ul><li> </li></ul><ul><li>[email_address] </li></ul>