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Decrease liquor in obg means

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Here is a complete explanation of Decrease in Liquor (Oligohydramnios) in Obstetrics & Gynecology:

Oligohydramnios - Decrease in Amniotic Fluid

Definition: A low volume of amniotic fluid for a given gestational age.
  • AFI (Amniotic Fluid Index) < 5 cm = Significant oligohydramnios
  • Normal AFI range: 8-24 cm (from 16 weeks onward)
  • Alternatively diagnosed by MVP (Maximum Vertical Pocket) < 2 cm

Causes

Amniotic fluid is mainly produced by fetal urine. So any decrease in fetal urine output or fluid loss leads to oligohydramnios:

Fetal Causes (Decreased Production)

  • Renal agenesis (Potter sequence) - no kidneys = no urine = severe oligohydramnios
  • Obstructive uropathy (posterior urethral valves, ureterocele) - urine can't pass out
  • Multicystic/dysplastic kidneys
  • Intrauterine Growth Restriction (IUGR) - ~83% of oligohydramnios cases (excluding PROM) have IUGR

Maternal/Placental Causes

  • Placental insufficiency (uteroplacental insufficiency) - reduced blood flow to fetus
  • Post-term pregnancy (>42 weeks) - placenta ages, perfusion drops

Fluid Loss

  • PROM (Premature Rupture of Membranes) - most common cause overall (~10% of pregnancies)
  • Amniotic leak

Drugs

  • ACE inhibitors / NSAIDs - can reduce fetal renal perfusion

Pathogenesis Diagram (from Robbins Pathology)

Oligohydramnios sequence pathogenesis - causes include uteroplacental insufficiency, renal agenesis, and amniotic leak leading to fetal compression and complications

Complications (from Fetal Compression)

ComplicationMechanism
Pulmonary hypoplasiaRestricted fetal breathing movements, especially if severe in 16-24 weeks (canalicular phase)
Potter facies (altered facies)Fetal compression by uterine wall
Positioning defects of hands/feet (clubfoot)Fetal compression
Breech presentationRestricted space
Amnion nodosumSquamous cell nodules on amnion surface
Umbilical cord compressionLess cushioning fluid
Pulmonary hypoplasia can be lethal if severe and early onset
Potter Sequence = renal agenesis → severe oligohydramnios → fetal compression → pulmonary hypoplasia + Potter facies + limb defects (lethal)

Intrapartum Complications

  • Fetal heart rate abnormalities
  • Depressed Apgar scores
  • Meconium passage

Diagnosis

  • Ultrasound - method of choice
    • AFI measurement (four-quadrant technique)
    • MVP (single deepest pocket)
  • Estimate fetal weight whenever oligohydramnios is found
  • Detailed anomaly scan to find cause

Management

  • At term: Oligohydramnios is generally an indication for delivery
  • Preterm: Depends on cause and severity - serial monitoring, treat underlying cause
  • Amnioinfusion (during labor) - saline infused into amniotic cavity to reduce cord compression and meconium aspiration
  • Treat IUGR, maternal hydration may help in some cases
  • Counsel for renal anomalies (urology/nephrology consult)
Key point for exams: The most common cause overall is PROM. Excluding PROM, the most common association is IUGR (83% of oligohydramnios cases have IUGR). Fetal renal causes are the classic causes taught in basic science.
  • Pfenninger and Fowler's Procedures for Primary Care, p. 5329-5341
  • The Developing Human - Clinically Oriented Embryology, p. 4376-4386
  • Robbins, Cotran & Kumar Pathologic Basis of Disease, Fig. 10.3
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