What is Oligohydramnios?

Medically Reviewed by Poonam Sachdev on April 08, 2022
Written by Alyssa Anderson
5 min read

Oligohydramnios is a condition you can develop when pregnant. It's the term for when you have too little amniotic fluid around your baby.  

It occurs in about 4% of to-term pregnancies, but it becomes more common — increasing to around a 12% chance — if your pregnancy is two weeks overdue.  

Low amniotic fluid levels are dangerous for your unborn child. The fluid protects your baby and gives it room for movement — letting their limbs grow and develop properly. It also helps with the development of their lungs, gastrointestinal tract, and kidneys. 

You begin making amniotic fluid 12 weeks after your baby is conceived. The amount steadily increases until it peaks at 36 weeks. Levels remain consistent for the next month and then start to decline. On average, one half to one full quart is the normal amount of amniotic fluid. 

Low fluid levels are defined as having too little fluid based on how far you are in your pregnancy. Some cases can be mild — with levels slightly below average. Other cases can be severe and indicate serious complications.  

Low levels of amniotic fluid might occur as isolated incidents. They can also be caused by birth defects or genetic conditions. In about 50% of all cases, the cause is unknown — this is called idiopathic oligohydramnios. 

After 14 weeks, almost all of the amniotic fluid is made of your baby’s urine — so any conditions that affect urine output are a possible cause of low fluid levels. 

Possible causes include: 

  • Carrying past your due date. In this case, the fluid loss is normal but can still be problematic.
  • Preterm rupture of the amniotic membrane. This is the cause in 37% of second and third-trimester cases. A tear allows the fluid to leak out. 
  • Placental abruption. This is the cause in 8.6% of cases. It occurs when your placenta detaches from your uterine lining.
  • Fetal birth defects. These tend to involve the kidneys or urinary tract. Your child’s kidneys may not be working correctly, their urinary tract may not have formed properly, or something may be physically blocking their urinary tract.  
  • Chromosomal abnormalities. These are found in 10% of cases detected in the second trimester. 
  • Twin-Twin Transfusion Syndrome. This is when nutrient distribution from a shared placenta is uneven. One twin gets too little and creates less amniotic fluid.
  • Maternal diabetes.
  • Chronic maternal high blood pressure.

Oligohydramnios is detected with an ultrasound. You may not know that you have the condition until you go in for a scheduled appointment and the technician notices that something is off. 

Ultrasound uses soundwaves to both detect amniotic fluid and measure how much is in your womb.   

If your technician detects low levels, it’s usually followed up with a pelvic exam — to check your amniotic sac for punctures or leaks. Other tests may be needed to help determine the cause.  

You might not notice any oligohydramnios symptoms on your own, but certain signs can lead your doctor to suspect this condition. 

These include: 

  • Fluid leaking from your vagina
  • Your uterus is smaller than it should be at your stage of pregnancy
  • You don’t feel your baby moving a lot
  • Your baby’s movement has decreased from previous levels

Too little amniotic fluid can be a very severe condition depending on when it begins in your pregnancy. In general, the earlier it happens, the more severe the complications can be. 

When oligohydramnios is detected within the second trimester, there’s only a 10.2% chance that your baby will survive. When it occurs in the third trimester, though, your baby has an 85.3% chance of survival.  

If fluid levels are low within the first six months, possible complications include: 

  • Preterm birth 
  • Miscarriage
  • Stillbirth
  • Developmental issues with the limbs and face from increased pressure in the womb
  • Infections — if the amniotic sac has torn early

If you develop this condition in your third trimester, complications can include: 

  • Umbilical cord compression — cutting off nutrients to your baby
  • Limitations to your baby’s growth
  • Problems with lung development and breathing
  • Increased risk of a Cesarean section (C-section)
  • Risk of an early delivery

The treatment plan for your oligohydramnios depends on how low the fluid levels are and when it occurs in your pregnancy. 

While you’re still pregnant, treatment might include: 

  • Frequent ultrasounds. These could be conducted on a weekly basis to evaluate your fluid levels and check on your baby’s development. 
  • Specialized ultrasounds. A technique called a doppler ultrasound can help your doctor see your placenta. This might be needed if your baby has stopped growing. 
  • Staying hydrated. Studies indicate that maternal hydration affects amniotic fluid levels later on in the pregnancy. So, make sure you drink plenty of water. 
  • Controlling underlying maternal conditions. If you have diabetes or high blood pressure, you’ll need to take steps to get these conditions under control.  
  • Fetal Interventions. These are needed if your baby’s urinary tract is blocked. 
  • Medications. These can help prepare your baby’s lungs for early delivery. 
  • Early delivery. This might be necessary to protect your baby from further complications, though it can cause complications of its own.  

If you’ve been diagnosed with oligohydramnios, you’re highly encouraged to give birth in a medical setting. This way, your medical team can prepare for — and immediately begin to treat — any of the complications that could occur. 

The exact steps that your medical team takes during and after the birth will vary from person to person and depend on the underlying cause. 

In the best-case scenario, your medical team will have determined the cause before birth but this isn’t always possible. This means that you’ll want a variety of resources on hand to deal with any possible developmental issues your baby may have. 

For example, if a birth defect is causing the condition, your child may need to immediately go to the intensive care unit (ICU) for treatment. Problems with their lung development or small size can also require attention in the ICU — like intensive breath support — before your baby is allowed to go home.  

When pregnant, you should always talk to your doctor or midwife if you have questions or concerns about your baby. 

You should get help immediately if you experience: 

  • Fluid leaking from your vagina
  • Bleeding from your vagina
  • Contractions
  • Cramps and pelvic pain
  • A decreased amount of movement from your baby