Oligohydramnios

Oligohydramnios is a condition in which there is too little amniotic fluid during pregnancy, the fluid that surrounds the developing fetus. Too little amniotic fluid can put both mother and baby at risk of complications.

The condition may be isolated, meaning there are no other health issues, or it may occur as a result of other fetal birth defects or genetic conditions.

While oligohydramnios can occur at any time during pregnancy, it is most common during the last trimester or in pregnancies that are past their due date. Generally, the earlier the condition occurs, the greater the risk to the developing baby.

The Importance of Amniotic Fluid

An adequate amount of amniotic fluid is vital to your baby’s health and development. As a result, amniotic fluid levels are regularly assessed during pregnancy to help identify any potential complications early.

Amniotic fluid consists primarily of fetal urine. During development, your baby breathes in and swallows amniotic fluid, helping the fetal lungs and other organs develop properly. The amniotic fluid and the baby are contained within the amniotic sac, sometimes referred to as the “bag of water,” inside the uterus.

Some important functions of amniotic fluid include:

• Development of the fetal lungs, digestive system and kidneys
• Provides room for fetal growth and movement, enabling proper muscle and limb development
• Protects the umbilical cord from being compressed, cutting off food and oxygen from the placenta to the growing fetus

Abnormal amniotic fluid levels during pregnancy include both oligohydramnios, where there is too little fluid, and a condition known as polyhydramnios, where there is too much amniotic fluid.

How does low amniotic fluid affect my baby?

Complications caused by too little amniotic fluid range from mild to severe, depending on the amount of fluid and the gestational age of the fetus.

Risks include: 

• Underdeveloped lungs (pulmonary hypoplasia) that are too small to support the baby’s oxygen needs at birth, causing respiratory distress
• Deformities of the limbs and face (known as Potter sequence) caused by the fetus being compressed in the womb and unable to move
• Inability to grow to normal size, known as intrauterine growth restriction (IUGR) or small for gestational age (SGA), where the fetal weight falls below the 10th percentile
• Preterm birth
• Need for cesarean delivery
• Labor complications, including umbilical cord compression, decreasing the oxygen and blood flow to the baby, and meconium (first stool) in the amniotic fluid, which can block the baby’s airways
• Stillbirth

Symptoms

Symptoms of low amniotic fluid during pregnancy may include:

• Fluid leaking from the vagina, caused by a tear in the amniotic membrane
• Uterus is too small for the stage of pregnancy
• Pregnancy weight is low
• Fetal movement is less than expected or the activity level decreases

Cause and Prevalence

Low amniotic fluid occurs in an estimated 4 percent of all pregnancies. The incident rate increases to 12 percent in pregnancies that are at least two weeks past their due date.

Any conditions that cause the fetus to produce less urine will reduce the amniotic fluid level.  

Causes of low amniotic fluid include:

• Birth defects of the kidneys or urinary tract, such as an obstruction in the fetal bladder or urethra, that reduce urine production or block the flow of urine into the amniotic sac
• Placenta problems that prevent the fetus from receiving blood and nutrients, such as placental abruption, where the placenta pulls away from the uterine wall before delivery
• Leaking from the vagina caused by a tear in the amniotic membranes (amniotic sac) or premature rupture of the membranes (PROM) (your water breaks early)
• A post-term pregnancy (42 weeks gestation or more)
• Maternal health conditions, including chronic high blood pressure (hypertension), preeclampsia and diabetes  
• Poor fetal growth (known as intrauterine growth restriction, or IUGR)
• Twin-twin transfusion syndrome (TTTS), a condition in which identical twins share one placenta and one twin receives too much blood and the other too little
• Certain medications taken during pregnancy

In many cases, the cause is unknown.

Diagnosis

Oligohydramnios is typically diagnosed during a routine ultrasound. The diagnosis is confirmed by measuring the volume of amniotic fluid in the uterus through more detailed ultrasound imaging.

A pelvic exam will also be performed to determine if the amniotic sac is leaking or ruptured too soon (your water broke). Blood tests may be run to look for underlying maternal conditions such as diabetes that can impact amniotic fluid.

If you are diagnosed with oligohydramnios, you may be referred to a fetal center for further evaluation and to look for any other fetal abnormalities.

At Texas Children’s Fetal Center, we arrange for you to visit as quickly as possible for a comprehensive assessment by a team of specialists experienced in diagnosing and treating these rare amniotic fluid conditions, including maternal-fetal medicine (MFM) physicians, fetal imaging experts, genetic counselors, neonatologists, and nephrologists (kidney specialists).

Additional testing may include:

• High-resolution anatomy ultrasound to evaluate the condition, assess fetal growth and development, and look for fetal anomalies such as malformations in the kidneys and urinary tract
• Ultra-fast MRI for a more detailed view of fetal anatomy and function
• Fetal echocardiogram to evaluate your baby’s heart structure and function
• Amniocentesis and chromosomal analysis to screen for genetic abnormalities
• Doppler ultrasound to evaluate blood flow from the placenta to the fetus

Our specialists will then meet with you about your results, answer any questions your family has, and discuss treatment recommendations based on your baby’s condition and any related abnormalities.

A diagnosis of any underlying fetal birth defects during pregnancy enables your family and your healthcare team to plan ahead for the special needs of your baby at birth and to arrange for the earliest possible treatment.

Treatment During Pregnancy

You and your baby will be closely monitored throughout pregnancy to watch for signs of complications. Testing may include:

• Frequent ultrasounds to assess fetal growth and amniotic fluid level
• “Nonstress” tests to monitor fetal activity and heart rate
• Doppler ultrasound to monitor placenta function if fetal growth restriction is noted  

Treatment during pregnancy will depend on the cause and severity of your baby’s condition and gestational age. Treatment options include:

• Maternal hydration to help increase amniotic fluid levels
• Treatment of underlying maternal conditions, such as diabetes and high blood pressure
• Fetal intervention for lower urinary tract obstructions (LUTO)
• Hospital admission if your membranes have ruptured, for close monitoring of preterm labor
• Medications to prepare your baby’s lungs for a possible early delivery
• Management of underlying birth defects or genetic abnormalities and preparations for advanced care and treatment at birth, to optimize fetal outcomes
• Early delivery, if needed, for the health and safety of you and your baby

Delivery

Babies with low amniotic fluid are at increased risk of respiratory problems at birth and may require immediate specialized treatment. We recommend delivery at a hospital with the expertise and resources required to treat these potentially high-risk deliveries, including the highest level neonatal intensive care unit (NICU), if needed.

Delivery and postnatal care should be carefully planned and coordinated with a team of maternal-fetal medicine specialists, neonatologists, and pediatric specialists experienced in working together to treat pregnancies involving rare amniotic fluid conditions, and any associated birth defects, ensuring the best possible care beginning at birth.

Our Fetal Center team works closely with pediatric experts from Texas Children’s Hospital, consistently ranked one of the best children’s hospitals in the nation by U.S. News & World Report.

Treatment After Birth

Treatment needs at birth vary for each baby depending on the underlying cause of the oligohydramnios, the gestational age when the low amniotic fluid first occurred, and the presence of any associated birth defects or genetic conditions.

In severe cases, treatment may include intensive breathing support due to underdeveloped lungs, specialized care in the NICU as a result of the baby’s small size, and surgery or advanced therapies for congenital abnormalities, such as birth defects of the kidneys or urinary tract.

Postnatal Care Team

A unique and distinct advantage for mothers delivering at Texas Children’s Pavilion for Women is our location inside one of the largest and most renowned children’s hospitals in the world, for seamless access to the critical care services and specialists your child may need.

For babies with rare fetal conditions such as oligohydramnios, this means no transfers during critical postnatal periods. It also means that the pediatric experts responsible for treating your child have been an integral part of their care team since before birth.

Your baby’s postnatal care team may include:

• Neonatologist
• Pediatric surgeon
• Cardiologist
• Pulmonologist
• Gastroenterologist
• Nephrologist (kidney disorders)

Texas Children’s is ranked number one in the nation in pediatric cardiology and heart surgery, number one in pulmonary care, number two in nephrology (kidney disorders) and number two in gastroenterology by U.S. News and World Report. All of the hospital’s subspecialties rank in the top 10.

Why Texas Children’s Fetal Center?

• A single location for expert maternal, fetal and pediatric care. At Texas Children’s Hospital, mother and baby can get the specialized care required for the diagnosis and treatment of oligohydramnios – and any underlying maternal or fetal conditions – all in one location, for highly coordinated care and treatment, including immediate access to our renowned level IV neonatal intensive care unit (NICU).
• A skilled, experienced team with proven outcomes. We have a dedicated team of maternal-fetal medicine specialists, fetal imaging specialists, neonatologists, genetic counselors, pediatric experts and others who work in concert to care for you and your baby every step of the way, using protocols we’ve developed over the years. With their combined expertise and unified approach, they offer the best possible care and outcomes for pregnancies complicated by oligohydramnios.
• We care for your child’s needs at every stage of life. Our comprehensive approach starts with your first prenatal visit and continues through your child’s delivery, postnatal care, and beyond, when needed, thanks to one of the nation’s leading teams of fetal and pediatric specialists for the treatment of rare fetal conditions and birth defects.