Oligohydramnios

Oligohydramnios is when you have too little amniotic fluid. Amniotic fluid is the fluid that surrounds your baby while they’re in your body before birth.

Your baby needs amniotic fluid to grow. This watery fluid is inside the amniotic sac (membrane). It’s sometimes called the bag of waters. Your baby stays in this fluid throughout your pregnancy. This helps protect your baby and allows them to move and kick during development. Amniotic fluid also helps your baby’s lungs, kidneys, and gastrointestinal (GI) tract grow. It’s very important for your baby’s development.

The fluid is made by your baby’s lungs and kidneys. Your baby swallows the fluid and passes it out as urine (pee). The baby also “breathes” the fluid into their lungs. The fluid pushes the air sacs in the lungs open and helps them grow. Your baby’s lungs grow a lot in the middle of the second trimester (16 to 24 weeks). If the amniotic fluid is too low during this time, your baby may not make enough lung tissue. This can cause breathing problems at delivery.

Oligohydramnios can happen at any time during pregnancy, but it’s most common in the last trimester (last 3 months). The risk of having oligohydramnios increases for people who are at least 2 weeks past their due dates. This is because the amount of amniotic fluid usually decreases by that time. In general, the earlier it happens during pregnancy, the higher the risk to the baby.

How do you know if you have oligohydramnios?

Amniotic fluid levels are checked regularly during pregnancy. Your health care provider uses ultrasound to measure the amount of amniotic fluid. If not enough amniotic fluid is seen on the ultrasound, you may have oligohydramnios.

There are two ways to measure the fluid: amniotic fluid index (AFI) and maximum vertical pocket (MPV). The AFI checks how deep the amniotic fluid is in four areas of your body. These amounts are then added up. If your AFI is less than 5 centimeters, you have oligohydramnios. The MPV measures the deepest area of your uterus to check the amniotic fluid level. If your MPV is less than 2 centimeters, you have oligohydramnios. Ask your provider if you have questions about these measurements

Ultrasound also shows how well your baby is growing. It can show the growth of your baby’s kidneys and urinary tract, and show urine in your baby’s bladder. You may need a special kind of ultrasound (Doppler flow study) to check blood flow through your baby’s kidneys and the placenta.

Other signs of oligohydramnios can include:

• The baby isn’t growing as fast as they should
• You’re leaking amniotic fluid, which may mean your sac has broken
• Your uterus is smaller than expected compared with how far along you are in your pregnancy or if you’re not gaining enough weight
• The baby isn’t moving around enough

If you notice fluid leaking, tell your health care provider right away.

What problems can oligohydramnios cause?

If oligohydramnios happens in the first 2 trimesters (first 6 months) of pregnancy, it is more likely to cause serious problems than if it happens in the last trimester. These problems can include:

• Birth defects of the limbs or face.
• Miscarriage, which is when a baby dies before 20 weeks of pregnancy
• Preterm birth, which is birth before 37 weeks of pregnancy
• Stillbirth, which is when a baby dies after 20 weeks of pregnancy
• Infection if the bag of waters is leaking

In general, babies who develop oligohydramnios after 23 to 24 weeks (6 months of pregnancy) usually don’t have breathing issues or other long-term problems. In some cases, oligohydramnios that happens in the third trimester of pregnancy can cause:

• The baby to grow too slowly
• Problems during labor and birth, such as the umbilical cord being squeezed. The umbilical cord carries food and oxygen from the placenta to the baby. If it’s squeezed, the baby doesn’t get enough food and oxygen.
• The baby to breathe their first bowel movement (meconium) into their lungs, which can cause breathing issues
• A greater chance of needing a Cesarean section (also called a C-section)
• Joint issues because the baby wasn’t able to move around enough

What causes oligohydramnios?

Sometimes the causes of oligohydramnios are not known. Some known causes are:

• Premature rupture of the membranes (PROM). This is when the amniotic sac around the baby breaks before you go into labor.
• Going past your due date (called post-term pregnancy). This is when your baby is born after 42 weeks, 0 days. A full-term pregnancy lasts between 39 weeks, 0 days and 40 weeks, 6 days.
• Birth defects, especially ones that affect the baby’s kidneys, stomach, bladder, or urethra.
• Issues with the baby’s placenta, which supplies the baby with food and oxygen through the umbilical cord
• Having a baby who is growing too slowly  
• Being pregnant with identical twins who share one placenta.
• Health problems, such as high blood pressure, preeclampsia, or preexisting diabetes
• Certain medications, like those used to treat high blood pressure (called ACE inhibitors) and pain relievers called non-steroidal anti-inflammatory drugs (NSAIDs)

How is oligohydramnios treated?

Treatment will focus on keeping you pregnant for as long as it’s safe. This will enable your baby to continue to grow and develop before birth. If you have a healthy pregnancy and get oligohydramnios near the end of your pregnancy, you probably don’t need treatment.

Treatment will depend on your symptoms, health, and how severe the condition is. It may include:

• Drinking water. Drinking lots of water may help increase the amount of amniotic fluid.
• Resting. Your provider may recommend less physical activity or going on bed rest.
• Monitoring. Your provider may want to see you more often. They may want to do ultrasounds weekly or more often to check the amount of amniotic fluid.
• Amnioinfusion. This is when the provider adds fluid by putting a saline solution (salty water) into the uterus through the cervix (the opening to the uterus that sits at the top of your vagina). You may need this if you’re in labor and your water has broken. It can help prevent some problems, such as the umbilical cord being squeezed. If the umbilical cord is squeezed, the baby doesn’t get enough food and oxygen.
• Medication. If you have diabetes or high blood pressure, your provider may treat those conditions. You may be given antibiotics to prevent infection if your amniotic sac has burst, or medication to help your baby’s lungs if the placenta isn’t working properly.
• Starting labor early. If the fluid gets too low or if your baby is having trouble staying healthy, your provider may recommend starting labor early to help prevent problems during labor and birth.

Getting early and regular prenatal care can help you have a healthy pregnancy and a full-term baby. Prenatal care is medical care you get during pregnancy. At each visit, your health care provider checks on you and your growing baby, including your amniotic fluid levels.

Call your provider and go for your first prenatal care checkup as soon as you know you’re pregnant. And go to all your prenatal care checkups, even if you’re feeling fine.

Last reviewed: February, 2023