Causes of Oligohydramnios
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Oligohydramnios has various causes, such as:
- Intrauterine growth retardation
- Intrauterine infection
- Severe fetal renal disease
- Amniotic fluid leak
- Twin/twin transfusion
- Chromosomal abnormalities
All of these conditions can lead to a reduction of fluid volume. Assessment of fluid volume is therefore critical, not only in growth retardation but also in the detection of major fetal abnormality.
In this example, the reduction in amniotic fluid is caused by obstruction to the fetal kidneys. Although the cause may influence the outcome in these babies, all cases of oligohydramnios should be referred to the specialist centre.
For all causes, fetal survival in this group is much worse than in the normal fetal population.
Intrauterine growth retardation
Placental dysfunction affects amniotic fluid production.
Intrauterine infection
Amnionitis reduces amniotic fluid production.
Severe fetal renal disease
Fluid made by the normal fetal kidneys contributes to amniotic fluid volume.
Amniotic fluid leak
A major leak of fluid or continued loss over a prolonged period can result in complete absence of fluid.
Twin/twin transfusion
One of the twins in this condition will be starved of nourishment and of fluid. The other twin sac may show polyhydramnios.
Chromosomal abnormalities
Some chromosomal abnormalities are associated with oligohydramnios.
