Oligohydramnios
Oligohydramnios is a condition in pregnancy characterized by a deficiency of amniotic fluid. It is the opposite of polyhydramnios.
Signs and symptoms
The common clinical features are smaller symphysio-fundal height, fetal malpresentation, undue prominence of fetal parts and reduced amount of amniotic fluid.
Complications
Complications may include cord compression, musculoskeletal abnormalities such as facial distortion and clubfoot, pulmonary hypoplasia and intrauterine growth restriction. Amnion nodosum is frequently also present (nodules on the fetal surface of the amnion).
The use of oligohydramnios as a predictor of gestational complications is controversial.
Potter syndrome is a condition caused by oligohydramnios. Affected fetuses develop pulmonary hypoplasia, limb deformities, and characteristic facies. Bilateral agenesis of the fetal kidneys is the most common cause due to the lack of fetal urine.
Causes
The cause is not known but is often associated with some:
- fetal chromosomal anomalies like triploidy
- intra uterine infections
- premature rupture of membrane
- drugs; COX inhibitors like indomethacin, ACE inhibitors
- renal agenesis or obstruction of the urinary tract of the fetus preventing micturition such as posterior urethral valves in males
- intrauterine growth restriction (IUGR) associated with placental insufficiency
- amnion nodosum; failure of secretion by the cells of the amnion covering the placenta
- postmaturity (dysmaturity)
Diagnosis
- uterine size is much smaller than the period of amenorrhoea
- fewer fetal movements,
- the uterus "full of fetus" because of scanty liquid,
- malpresentation (breech)
- evidences of IUGR of the fetus,
- sonographic diagnosis is made when largest liquid pool is less than 2 cm,
- visualization of normal filling and emptying of fetal bladder essentially rule out urinary tract abnormality,
- Oligohydramnios with fetal symmetric growth retardation is associated with increased chromosomal abnormality.
Treatment
A Cochrane review concluded that "simple maternal hydration appears to increase amniotic fluid volume and may be beneficial in the management of oligohydramnios and prevention of oligohydramnios during labour or prior to external cephalic version."
In severe cases oligohydramnios may be treated with amnioinfusion during labor to prevent umbilical cord compression. There is uncertainty about the procedure's safety and efficacy, and it is recommended that it should only be performed in centres specialising in invasive fetal medicine and in the context of a multidisciplinary team.
In case of congenital lower urinary tract obstruction, fetal surgery seems to improve survival, according to a randomized yet small study.
See also
- Fetal intervention
- Potter's sequence