In the womb, the baby is surrounded by, and floats in, a sac filled with amniotic fluid. This fluid acts to protect the foetus from bumps and jarring, recirculates waste, and acts as a fluid for the baby to drink. If insufficient of fluid is present, the condition is called oligohydramnios.
Normally there is about a litre (1000 mL) of amniotic fluid at birth. A volume of less than 200 mL is considered to be diagnostic of oligohydramnios. It may be caused by abnormal development of the foetus, or abnormal function of the placenta, but in most cases, there is no reason for the problem.
The condition is diagnosed by an ultrasound scan, and if proved, further investigations to determine the cause of the condition follow. Treatment will depend upon the result of these tests, but often none is necessary.