- Oligohydramnios can be defined as a reduced Amniotic Fluid Index <5th centile for the appropriate gestation ( ~ < 200mls)
- This may be apparent from a history of preterm prelabour rupture of membranes (PPROM) or on abdominal examination
when obvious foetal poles can be palpated
- The causes of oligohydramnios are shown below:-
a) Reduced production of amniotic fluid
- Abnormalities of the genitourinary system - urethral aplasia / obstruction due to posterior urethral valves
- Renal agenesis / Multicystic Kidneys
- Placental insufficiency
- Prolonged rupture of membranes
- Prolonged pregancy
- Intrauterine Growth Retardation (IUGR)
- Maternal use of NSAID's or ACE-Inhibitors
- Potter's Syndrome - fatal syndrome comprising of foetal renal agenesis, hypoplastic lungs, amnion nodosum, low and wide set ears, flattened nose
b) Loss of amniotic fluid
- Preterm prelabour rupture of membranes
Complications
- These ultimately depend on the underlying cause of the oligohydramnios
- Limb deformities - contractures, talipes are common if the onset is early (<24 wks), but if caused by placental insufficiency or IUGR limb deformities are less common
- Pulmonary hypoplasia can also occur leading to respiratory distress of the baby at delivery
- Renal agenesis ultimately leads to death
- Oligohydramnios can also be associated with an increased risk of foetal distress in labour
Investigations
- Ultrasound scan - to assess the level of amniotic fluid, the foetal urogenital system, and assess placental sufficiency
Management
- Encourage rest, and good fluid intake
- Regular antenatal ultrasound scans to monitor progress of the baby and the level of amniotic fluid
Bibliography
Campbell S, & Lees C. Obstetrics by Ten Teachers - 17th Edition. Arnold, London, 2000.
Collier J, Longmore M & Brown TD. Oxford Clinical Handbook of Clinical Specialties - 5th Edition, Oxford University Press, 1999.
Impey L. Obstetrics and Gynaecology. Blackwell Science Ltd, 1999.
Dr. N Sparrow - January 26th 2006
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