Amniotic fluid disorder

• Amniotic fluid


  Also termed as liquor amnii, is the fluid which distends the amniotic sac and allow the growth and free movement of fetus. It is a clear, pale straw-colored fluid, consisting 99% water. Remaining 1% is dissolved in solid matter including food substances and waste product.
• Amniotic fluid normally increases in amount throughout pregnancy from few milliliters to a liter at 38th week
• The water and solutes in amniotic fluid are changing every few hours
• Polyhydramnios (hydramnios)


  An excessive amount of amniotic fluid, which exceeds 1500 ml. It occurs in 0.9% of pregnancies. Polyhydramnios is present when AFI is more than 25 cm and the MVP (maximum vertical pocket) measures more than 8cm.
• Oligohydramnios


  An abnormally low amount of amniotic fluid. At term it may be 300-500ml, but the amount can be even less. Occurs in 10% of all pregnancies.
• Causes of Polyhydramnios


  • Fetal malformation: esophageal atresia, open neural tube defect, anencephaly (35%)
  • Maternal Diabetic mellitus (25%)
  • Other: maternal anemia, twin to twin transfusion syndrome or fetal tumor
  • Unknown (40%)
• Types of Polyhydramnios


  • Chronic Polyhydramnios - Gradual in onset, usually from about 30th week of pregnancy, most common type
  • Acute Polyhydramnios - Very rare, occurs at about 20th week and comes on very suddenly, often associated with monozygotic twins and/or severe fetal abnormalities
• Manifestations of Polyhydramnios


  • Uterine enlargement - fundal height more than expected
  • Tense uterine wall making difficult to auscultate
  • Uterine fluid thrill
  • Unstable lie
  • Dyspnea, nausea and vomiting
  • Pain at back, thigh and abdomen due to pressure
  • Lower extremities and vulva edema
• Diagnosis of Polyhydramnios


  • Ultrasound scanning (sonogram)
  • Screening for diabetes
  • Screening for ABO/Rh disease
  • Suspect when uterine size is larger than expected for dates
  • Amniotic fluid is quantitatively measured, using the amniotic fluid index (AFI) in all suspect cases
  • Clinical findings: stretch and shiny abdomen, tenderness on palpation, fluid thrill, difficult to hear fetal heart sound
• Management of Polyhydramnios


  • For woman with mild asymptomatic Polyhydramnios: Advised to get adequate rest, advised to immediately admit if membrane ruptures
  • For woman with symptomatic Polyhydramnios: Admission to hospital required, care depends on condition of mother and fetus, causes and degree of hydramnios and the stage of pregnancy, upright position to relieve dyspnea, antacid may be prescribed, remote term with severe discomfort - amniocentesis and amnioreduction (500ml), control drainage of fluid in case of ARM, if term plan for delivery
• Causes of Oligohydramnios


  • Fetal Congenital abnormalities like renal agenesis (absence of kidney at birth), Potter's syndrome (pulmonary hypoplasia - lungs are abnormally small)
  • Early rupture/leakage of membrane (24-26 weeks)
  • Post dated pregnancy
  • IUGR related to impaired placental insufficiency, decrease in fetal urine formation leads to oligohydramnios
  • Pre-eclampsia
• Clinical manifestations of Oligohydramnios


  • Uterus smaller to its gestation
  • Reduced fetal movement
  • Fetal parts are easily felt
  • Non-ballotable of fetus
  • FHS clear or increase due to distress
• Management of Oligohydramnios


  • Depends on gestation: Early tear - probably miscarriage, second term - fetal dead or malformation, if agenesis not present - placental function tests performed, increase fluid intake or intravenous hypotonic fluid, where fetal anomalies not lethal - amnioinfusion with normal saline or Ringer's lactate, third trimester - aim in maturation of fetal lungs and induce labor, epidural analgesia preferred during labor, monitor for fetal wellbeing and meconium stained
• Complications of Oligohydramnios


  • Limb deformities e.g. talipes
  • A squashed looking face, flattening of the nose and micrognathia (small jaw)
  • Dry, leathery skin
• Maternal risk factors associated with amniotic fluid disorders include diabetes mellitus and gestational diabetes
• Oligohydramnios is associated with gestational age at term and neonatal birth weight less than 2.5kg, while Polyhydramnios is associated with gestational age at term and neonatal birth weight more than 2.5kg
• Cesarean section was higher among pregnancies complicated by Polyhydramnios, while vaginal deliveries were mostly associated with Polyhydramnios