Oligohydramnios is a disorder that occurs in pregnancy and is characterized by an amniotic fluid deficiency. The fetuses with this condition have less than 500 ml of amniotic fluid .
The prevalence of this disease can be up to 6% of all pregnancies .
There may not be any prominently detectable signs in affected women. Lack of amniotic fluid is one of the common signs. Some other common problems include :
- Abnormal protuberance of fetal parts
- Fetal malpresentation
- Shorter symphysis-fundus height
In some cases, there might be some physical symptoms like:
- Persistently wet sensation in case of a ruptured amniotic sac, due to leakage of vaginal fluid.
- Apparently smaller appearance of the belly than what should be at a certain gestational stage.
Oligohydramnios is mainly idiopathic in nature. Experts are still trying to ascertain the exact cause for the symptoms. The contributory factors involve:
Ruptured or leaky amniotic membranes
In some cases, Oligohydramnios may occur due to leakage of amniotic fluid through a small ruptured spot in the amniotic membranes. This is quite common during the time of delivery although it may arise at any stage of pregnancy .
Kidney defects (polycystic kidney, renal agenesis) or absence of kidney in a fetus may also affect urine production.
Inheritance (autosomal recessive/autosomal dominant) of abnormal genes by a baby may also be a cause.
Risk of amniotic fluid deficiency is higher in women carrying multiple fetuses or twins. Oligohydramnios may also arise due to Twin-to-twin transfusion syndrome, a disorder characterized by high fluid levels in one twin and severe lack of amniotic fluid in another.
Amniotic fluid deficiency may arise due to placental abnormalities such as a partial abruption, which results in peeling of the placenta from the inner uterus wall . Acute complications may arise from stoppage of urinary production due to abnormality in the placental blood and nutrient supply.
These include use of non-steroidal anti-inflammatory medications (NSAIDs) such as:
- Some angiotensin-converting enzyme (ACE) inhibitors
Oligohydramnios Risk Factors
Risk is higher in babies born to mothers suffering from the following disorders :
- Chronic high blood pressure
This helps in:
- Checking fetal growth
- Ruling out other disorders (cystic dysplasia, ureteral obstruction, renal agenesis etc.)
- Determine placental insufficiency (by using Doppler ultrasound) 
Diagnostic criteria involve:
- < 5 cm amniotic fluid levels
- Lack of a fluid pocket (about 2-3 cm deep)
- < 500mL total amniotic fluid volume from 32-36th gestational weeks
Maximum Vertical Pocket (MPV)
It lets doctors assess amniotic fluid levels in the deepest uterine sections.
Amniotic Fluid Index (AFI)
It is one of the most common tests  available for amniotic fluid volume (AFV) measurement. Oligohydramnios is diagnosed in 4% of approximately 8% pregnant women with amniotic fluid deficiency.
Sterile Speculum Examination
It helps to spot any rupture of membranes (ROM) that might have caused Oligohydramnios.
Maternal Blood Test
Amniotic fluid deficiency in the uterus can be detected by blood tests, such as maternal serum screening. These also help understand the risk of an infant to be born with congenital disorders (Spina bifida, Down syndrome etc).
Oligohydramnios Differential Diagnosis
This should aim at distinguishing the signs of from those of similar disorders like cystic dysplasia, as is done during ultrasound examination.
Mild oligohydramnios in the later stages of a healthy pregnancy does not require any treatment. Tests in these stages include:
- Assessment of lung development
- Monitoring the fetal heart rate
- Determining movements of a baby (with ultrasound and similar exams)
If oligohydramnios arises during the last trimester, delivery is the most suitable management option. More acute cases of pre-term oligohydramnios may need the following treatment options:
Normalcy of amniotic fluid levels are maintained by infusing sodium chloride solution into the amniotic cavity by use of an intrauterine catheter .
It includes diverting the fetal urine into the uterus in sufferers of fetal obstructive uropathy – a condition which results in oligohydramnios. Amniotic fluid levels can also be effectively managed with Vesico-amniotic shunts, although their effectiveness in maintaining proper pulmonary and renal functions is still doubtable.
This involves injecting fluids through amniocentesis before delivery. It helps physicians understand the fetal anatomy better so as to help them to manage the problem better afterwards. The disorder, however, recurs within a few weeks after injection.
The body of a mother is rehydrated and amniotic fluid levels are increased through the use of oral and IV fluids. Mothers are recommended to increase their fluid consumption.
Complete bed rest, along with proper fluid intake, helps boost amniotic fluid production by increasing the intravascular space .
Only in severe cases during the first trimester, termination of pregnancy may be recommended.
The outcome is very poor where pulmonary hypoplasia is associated. The earlier Oligohydramnios develops in pregnancy, the poorer the prognosis is. The risk of recurrence in future pregnancies depends on the exact causes .
Oligohydramnios and Life Expectancy
Fetal mortality rate varies between 80-90% in cases where Oligohydramnios is detected as late as during the second trimester.
The possible complications include:
- Amniotic band syndrome
- Pulmonary hypoplasia
- Fetal compression syndrome
- Miscarriage in up to 95% sufferers due to first trimester oligohydramnios
- Heightened risk of fetal infections (for prolonged amniotic membrane rupture)
Prevention is totally unlikely in idiopathic cases although the risks might be lowered with certain measures  like:
- Not smoking
- Working out regularly
- Drinking lots of fluids to prevent dehydration
- Going for regular check-ups to spot any fetal abnormality (screening tests)
- Sticking to a healthy diet (particularly recommended for diabetic women)
- Consulting a doctor before using any medications, herbal supplements or vitamin supplements
The images below show the appearance of Oligohydramnios sufferers.
Picture 1 – Oligohydramnios
Picture 2 – Oligohydramnios Image
Oligohydramnios Support Groups
For information and guidance, family members of patients can contact:
March of Dimes National Office
1275 Mamaroneck Avenue
White Plains, New York State 10605
Phone: (914) 997-4488
Oligohydramnios ICD9 Code
The ICD9 Code of the disorder is 658.0.