Definition - What does Anhydramnios mean?

Anhydramnios is defined as the absence of the amniotic fluid (liquor amnii) which is normally contained within the bag of waters and surrounds the fetus. Any condition that involves a tear in the placenta or is related to oligohydramnios, can result in anhydramnios. Oligohydramnios is the lack of adequate amniotic fluid. Ruptured or leaked membranes, impaired placental function, or abnormalities in the developing fetus’s kidneys or urinary tract can interfere with the production of amniotic fluid.

FertilitySmarts explains Anhydramnios

The amniotic fluid cushions the fetus from blows and aids in body and lung development. The fluid is passed as urine via the fetal kidneys and then recycled to be swallowed. Hence, kidneys contribute to a large volume of amniotic fluid. Since fetal kidneys are the main source of the amniotic fluid, blockage of the urinary tract can lower the amniotic fluid levels to dangerous levels.

A number of conditions can lower the amniotic fluid levels. These include:

  • Preterm premature rupture of membranes (PPROM) - rupture of the membranes surrounding the baby before the onset of uterine contractions causes the leakage of amniotic fluid. This leakage can be severe enough so that no more amniotic fluid is left behind.
  • Failure of the placenta to supply oxygen and nutrients to the fetus
  • Silent rupture of the uterus
  • A large ureterocoele that obstructs the urinary tract on both sides. Ureterocoele is a birth abnormality where the lower portion of the ureter (tube extending from the kidneys to the bladder) enlarges at its opening into the bladder.
  • Posterior urethral valve (with complete blockage) - a birth abnormality in male babies in which a membrane obstructs the urethra.
  • Use of certain medications like painkillers and chemotherapy agents during pregnancy can also contribute to anhydramnios

The mother may experience decreased fetal movements and the size of the uterus may be smaller than expected for the stage of pregnancy. Anhydramnios is a life-threatening condition for both the mother and baby and when present, warrants urgent treatment. The amniotic fluid volume can be assessed with the help of serial ultrasound examinations. This is represented by the amniotic fluid index (AFI), which is the aggregate of the vertical depth of fluid in all the four sections of the uterus. No detectable fluid indicates anhydramnios.

Several complications can occur due to anhydramnios, such as:

  • Potter syndrome - the most common complication of anhydramnios characterized by the absence of both the kidneys and limb abnormalities in the baby
  • Failure of the baby’s lungs to develop properly causing respiratory distress at birth. A protein present in the amniotic fluid is required by the baby’s lungs to grow properly. A shortage of amniotic fluid will interfere with the proper development of the baby’s lungs
  • Growth restriction of the fetus while in the uterus
  • Premature labor
  • Compression of the umbilical cord - results in baby's death if not treated immediately

Anhydramnios also increases the likelihood of miscarriage. Amnioinfusion, a procedure in which fluid is infused into the bag of waters, may provide a cushion around the baby and umbilical cord. Delivery is the mainstay of treating anhydramnios.

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