Oligohydramnios

Oligohydramnios is a condition in which there is less amniotic fluid than is expected for the gestational age. Etiologies include fetal conditions such as renal tract abnormalities, chromosomal abnormalities, and congenital infections, and maternal conditions such as placental insufficiency, late or postterm pregnancy, and premature rupture of the membranes. Oligohydramnios is suspected if abdominal girth and symphysis-fundal height are smaller than expected for gestational age, but ultrasound to measure the amniotic fluid index is required to confirm the diagnosis. Treatment varies depending on gestational age; amnioinfusion can be used to reduce complications in early pregnancy, whereas induction of labor may be appropriate in late pregnancy. Complications include intrauterine growth restriction, Potter sequence, and complications during labor and delivery, e.g., umbilical cord compression.

• Fetal anomalies
  • Urethral obstruction (e.g., posterior urethral valves)
  • Bilateral renal agenesis
  • Autosomal recessive polycystic kidney disease (ARPKD)
  • Chromosomal aberrations (e.g., trisomy 18)
  • Congenital infections (e.g., TORCH infections)
  • In multiple pregnancies: twin-to-twin transfusion syndrome
• Maternal conditions
  • Placental insufficiency
  • Late or postterm pregnancies (> 42 weeks of gestation)
  • Premature rupture of membranes
  • Preeclampsia
• Idiopathic

• Small abdominal girth and uterine size for gestational age
• Ultrasound: Determine amniotic fluid and assess for fetal anomalies.
• Amniotic fluid index (AFI): a semiquantitative tool used to assess amniotic fluid volume (normal range: 8–18 cm)
  • Determined by dividing the uterus into 4 quadrants, holding the transducer perpendicular to the patient's spine, and adding up the deepest vertical pocket of fluid in each quadrant
  • Oligohydramnios: ≤ 5
  • In pregnancies < 24 weeks and multiple gestations, the single deepest pocket is used (normal range: 2–8 cm).

• Amnioinfusion: infusion of fluid into the amniotic cavity through amniocentesis
• Treat underlying cause: See “Preeclampsia,” “Premature rupture of membranes,” and “Placental insufficiency.”
• Delivery is advised if the fetus is close to term.

• Intrauterine growth restriction (due to diminished mobility of the fetus)
• Birth complications (e.g., umbilical cord compression)
• Potter sequence
  • Etiology
    • Chronic placental insufficiency
    • ↓ Renal output (e.g., due to bilateral renal agenesis, ARPKD, obstruction of posterior urethral valves)
    • Chronic amniotic fluid leakage
  • Pathophysiology: oligohydramnios → intrauterine compression and decreased amniotic fluid ingestions → ↓ space for fetal development → internal and external deformations
  • Clinical features
    • Pulmonary hypoplasia (cause of death due to severe neonatal respiratory insufficiency)
    • Craniofacial abnormalities (e.g., prominent epicanthal and infraorbital folds, flattened nose, receding chin, low set ears)
    • Wrinkling of the skin
    • Limb anomalies (e.g., bowed legs, clubbed feet)

Potter babies cannot Pee.

POTTER sequence: Pulmonary hypoplasia (lethal), Oligohydramnios (origin), Twisted facies, Twisted skin, Extremity deformities, and Renal agenesis (classic form).

We list the most important complications. The selection is not exhaustive.