Hydrocephalus in pregnancy, also called fetal hydrocephalus, refers to an abnormal buildup of cerebrospinal fluid (CSF) in the spaces inside a developing baby's brain. It may be suspected during a prenatal ultrasound that shows enlarged brain ventricles. However, enlarged ventricles, known as ventriculomegaly, do not always mean that a baby has hydrocephalus.
The cause, degree of enlargement, associated findings, and changes over time help doctors determine what the diagnosis means for the baby. Hydrocephalus cannot always be prevented, although taking folic acid before and during early pregnancy can reduce the risk of certain neural tube defects associated with some cases. When fetal hydrocephalus is suspected, coordinated care involving maternal-fetal medicine specialists, obstetricians, neonatologists, and pediatric neurosurgeons helps families understand the findings and plan for care after birth.
At New Jersey Pediatric Neuroscience Institute (NJPNI), families can learn about pediatric neurological and neurosurgical care, including evaluation and treatment options for children with hydrocephalus.
What Is Fetal Hydrocephalus?
Cerebrospinal fluid is a clear fluid that circulates through the brain's ventricles and around the brain and spinal cord. It cushions the nervous system, helps maintain its chemical environment, and is continuously produced and reabsorbed.
Hydrocephalus develops when CSF accumulates abnormally, causing enlargement of the ventricles and, in some cases, increased pressure on surrounding brain tissue.
During pregnancy, an ultrasound may reveal enlarged ventricles. This finding is called ventriculomegaly. It can have several causes and does not automatically indicate progressive hydrocephalus or predict a particular outcome.
Doctors assess the degree of ventricular enlargement, examine the baby's brain and other anatomy, and consider whether there are associated conditions. Follow-up imaging and specialist consultations help determine whether the finding is stable, progressing, or part of a broader condition.
Parents who receive an unexpected prenatal finding can learn more about NJPNI's Hydrocephalus Center, which provides information about pediatric hydrocephalus evaluation, treatment, and ongoing care.
What Causes Hydrocephalus During Pregnancy?
Fetal hydrocephalus can develop for several reasons. In some cases, the cause is identified during prenatal evaluation; in others, it remains uncertain.
1. Blockage of Cerebrospinal Fluid Flow
A blockage in the normal pathway of CSF can prevent fluid from circulating properly. One example is aqueductal stenosis, in which the narrow channel connecting parts of the brain's ventricular system is abnormally narrow or obstructed.
The effect depends on the location and severity of the blockage and whether other brain abnormalities are present.
2. Neural Tube Defects, Including Spina Bifida
Some neural tube defects are associated with changes in brain development and CSF circulation. Myelomeningocele, a form of spina bifida, can occur alongside Chiari II malformation and hydrocephalus.
When spina bifida is identified during pregnancy, the care team may recommend additional imaging, counseling, and discussions about treatment options before and after birth.
Families can explore NJPNI's Pediatric Spina Bifida Center for information about evaluation and care for children with spina bifida.
3. Infections During Pregnancy
Certain infections can affect fetal brain development. These include cytomegalovirus (CMV) and toxoplasmosis, which may be investigated when prenatal imaging shows ventriculomegaly or other findings that raise concern for fetal infection.
The need for testing depends on the clinical situation and should be discussed with the maternal-fetal medicine team.
4. Bleeding in the Developing Brain
Bleeding within the fetal brain can interfere with CSF circulation or absorption and may contribute to ventricular enlargement or hydrocephalus.
The significance depends on the location and extent of the bleeding and any associated changes in brain development.
5. Genetic Conditions and Other Brain Abnormalities
Some genetic conditions and congenital differences in brain development are associated with ventriculomegaly or hydrocephalus. Further assessment may include a detailed fetal ultrasound, genetic counseling, and diagnostic testing when appropriate.
6. Other or Unidentified Causes
In some pregnancies, the cause of enlarged ventricles or hydrocephalus cannot be established, even after evaluation. The absence of a clear cause does not, by itself, determine the baby's prognosis.
Can Hydrocephalus Be Prevented During Pregnancy?
Hydrocephalus cannot always be prevented. Some causes are related to genetic factors or structural differences that cannot be avoided. However, certain steps before conception and during pregnancy can reduce the risk of some associated conditions and support early detection.
Take Folic Acid Before and During Early Pregnancy
Folic acid helps reduce the risk of neural tube defects, including spina bifida, which may be associated with hydrocephalus.
The CDC recommends that women who could become pregnant take 400 micrograms (mcg) of folic acid daily. It is particularly important to begin before conception and continue during early pregnancy. Some people may need a different dose based on their medical history, so discuss individual recommendations with your healthcare professional.
Folic acid does not prevent every type of hydrocephalus.
Attend Routine Prenatal Appointments
Regular prenatal care helps clinicians monitor pregnancy and identify findings that may require further evaluation. If an ultrasound suggests enlarged fetal ventricles, the obstetric team may arrange a detailed examination and referral to a maternal-fetal medicine specialist.
Discuss Infection Risks and Vaccinations
Ask your prenatal care provider about recommended vaccinations, infection prevention, and any specific exposures that may be relevant during pregnancy. Not all fetal infections can be prevented, but appropriate precautions and timely assessment can help manage certain risks.
Seek Preconception or Genetic Counseling When Appropriate
If a previous pregnancy involved a neural tube defect, hydrocephalus, or a genetic condition, preconception counseling may help clarify recurrence risks and available testing options. Recommendations should be tailored to the specific diagnosis and family history.
How Is Hydrocephalus Diagnosed During Pregnancy?
Prenatal ultrasound is usually the first test used to identify enlarged fetal ventricles. Further evaluation helps determine whether the finding represents isolated ventriculomegaly, hydrocephalus, or another developmental condition.
Prenatal Ultrasound
During an ultrasound, clinicians examine the baby's brain structures and measure the ventricles. If the ventricles appear enlarged, a detailed fetal ultrasound may be recommended to assess their size and look for other anatomical findings.
The measurements, appearance of the surrounding brain, and changes over time all contribute to the assessment.
Fetal MRI
Fetal magnetic resonance imaging (MRI) may be recommended when additional detail about the brain is needed. It can help identify associated abnormalities that may not be fully characterized by ultrasound.
Whether fetal MRI is appropriate depends on the ultrasound findings, the stage of pregnancy, and the availability of specialist interpretation.
Genetic and Infection Testing
When ventriculomegaly is detected, clinicians may discuss genetic counseling, diagnostic testing, and testing for certain fetal infections. These investigations help identify possible underlying causes and inform counseling about outcomes.
Not every baby needs every test. The evaluation should be individualized according to the findings and the family's circumstances.
How Is Hydrocephalus Monitored During Pregnancy?
Once enlarged ventricles or suspected fetal hydrocephalus have been identified, the care team may recommend follow-up ultrasound examinations to monitor changes over time.
Monitoring can help clinicians determine whether the ventricles remain stable, increase in size, or are accompanied by additional findings. The schedule of examinations depends on the degree of enlargement, the suspected cause, and the overall pregnancy.
Depending on the results, the care team may include:
- An obstetrician or maternal-fetal medicine specialist.
- A fetal imaging specialist or radiologist.
- A neonatologist to plan newborn care.
- A pediatric neurosurgeon to discuss possible treatment after birth.
- A genetic counselor when an inherited or chromosomal condition is suspected.
There is no single monitoring schedule or delivery plan that is appropriate for every pregnancy. The recommendations should be based on the individual findings and the health of both the pregnant person and the baby.
Can Fetal Hydrocephalus Be Treated Before Birth?
In most cases, fetal hydrocephalus is monitored during pregnancy, and treatment decisions are made in preparation for care after delivery.
There are specialized fetal interventions for certain conditions, including selected cases involving spina bifida, but these are not routine treatments for every case of fetal hydrocephalus. Eligibility depends on the diagnosis, gestational age, maternal health, and the expertise of a specialized fetal treatment center.
If the ventricles continue to enlarge or additional abnormalities are identified, the medical team will explain the findings, discuss the possible implications, and determine whether changes to the pregnancy management plan are needed.
The timing and mode of delivery should be decided by the obstetric team based on standard obstetric indications and the specific clinical circumstances. A prenatal diagnosis of ventriculomegaly does not automatically mean that early delivery or cesarean delivery is required.
How Is Hydrocephalus Treated After Birth?
After delivery, the newborn's care team assesses the baby's neurological condition and determines whether additional imaging is needed. Some babies with mild or isolated ventriculomegaly may need monitoring rather than surgery. Babies with progressive hydrocephalus or signs of increased pressure may require treatment.
A pediatric neurosurgeon helps determine whether intervention is necessary and which approach is appropriate.
Ventriculoperitoneal Shunt
A ventriculoperitoneal (VP) shunt is a device that drains excess CSF from the brain's ventricles into the abdominal cavity, where the fluid can be absorbed.
A shunt may be recommended when hydrocephalus requires ongoing drainage. It needs regular medical follow-up because complications, such as blockage, infection, or malfunction, can occur.
Endoscopic Third Ventriculostomy
Endoscopic third ventriculostomy (ETV) is a surgical procedure that creates an opening in the floor of the third ventricle to provide an alternative route for CSF flow.
ETV is suitable for certain types of hydrocephalus, but it is not appropriate for every baby. The decision depends on the underlying cause, the child's age, and the anatomy of the ventricular system.
The pediatric neurosurgery team explains the potential benefits, risks, and alternatives before recommending a procedure.
For more information about available care, visit NJPNI's Pediatric Neurosurgery service or the Hydrocephalus Center.
What Is the Outlook for Babies With Hydrocephalus?
The outlook varies according to the cause of hydrocephalus, the degree of ventricular enlargement, associated brain or genetic conditions, and whether complications develop.
Some children respond well to treatment and make substantial developmental progress. Others may need long-term monitoring, additional procedures, rehabilitation, or support for developmental difficulties.
Prenatal imaging helps identify concerns, but it cannot always predict an individual child's long-term outcome. Follow-up after birth allows clinicians to assess the child's needs and recommend appropriate care as development progresses.
Early recognition of developmental or neurological concerns can help families access support when needed. The care plan may involve pediatric neurosurgery, neurology, physical therapy, or other services, depending on the child's individual circumstances.
How Can Parents Prepare for a Baby With Suspected Hydrocephalus?
A prenatal diagnosis or ultrasound finding can be stressful. Having a clear plan and knowing which professionals to contact can help families prepare for delivery and newborn care.
Consider these steps:
- Ask for an explanation of the imaging findings. Find out whether the report describes ventriculomegaly or confirmed hydrocephalus, how severe the finding is, and whether other abnormalities were identified.
- Discuss additional tests. Ask whether a detailed ultrasound, fetal MRI, genetic counseling, or infection testing is appropriate.
- Plan follow-up appointments. Confirm how often the baby will be monitored during pregnancy and which changes should prompt reassessment.
- Discuss care after birth. Ask whether newborn imaging, a neonatal assessment, or a pediatric neurosurgical consultation is likely to be needed.
- Keep copies of medical reports. Having ultrasound reports and other relevant records available can help the care team coordinate evaluations.
Families can review the NJPNI team and its specialties to learn more about pediatric neurological and neurosurgical care. Dr. Catherine Mazzola, MD, FAANS, is a pediatric neurosurgeon whose listed clinical interests include hydrocephalus and spina bifida.
Frequently Asked Questions About Hydrocephalus in Pregnancy
Can hydrocephalus be prevented during pregnancy?
Not every case can be prevented. Taking folic acid before conception and during early pregnancy reduces the risk of neural tube defects, including spina bifida, which can be associated with hydrocephalus. Prenatal care and appropriate screening can also help identify concerns early.
How is fetal hydrocephalus diagnosed?
Fetal hydrocephalus may be suspected when a prenatal ultrasound shows enlarged brain ventricles. A detailed ultrasound, fetal MRI, and additional investigations may be recommended to clarify the diagnosis, identify associated abnormalities, and assess possible causes.
Does ventriculomegaly always mean hydrocephalus?
No. Ventriculomegaly describes enlarged brain ventricles and can have several causes. It does not automatically mean that CSF pressure is increasing or that surgery will be required. The degree of enlargement, associated findings, and changes over time help guide the assessment.
Can a baby with hydrocephalus live a normal life?
Some children with hydrocephalus make good developmental progress, particularly when the condition is recognized and appropriately managed. Outcomes vary depending on the underlying cause, severity, associated conditions, and response to treatment. Long-term follow-up may be needed.
Is hydrocephalus treated before or after birth?
Most babies are monitored during pregnancy and assessed for treatment after birth. Selected fetal conditions may have specialized prenatal treatment options, but these are not routine for every case of hydrocephalus. The care team will discuss the options appropriate to the specific diagnosis.
Will a baby with fetal hydrocephalus need surgery?
Not every baby with enlarged ventricles needs surgery. If progressive hydrocephalus or increased pressure develops, a pediatric neurosurgeon may recommend a procedure such as a VP shunt or, in selected cases, ETV. The decision depends on the baby's individual diagnosis and clinical findings.
Concerned About a Prenatal Scan? Learn About Your Options at NJPNI
If a prenatal scan has raised questions about your baby's brain development, your obstetric or maternal-fetal medicine team can explain the findings and coordinate the appropriate next steps.
NJPNI provides pediatric neurological and neurosurgical care, including evaluation and treatment for children with hydrocephalus. Our team can help families understand pediatric neurosurgical options and prepare for a child's care after birth when specialist evaluation is appropriate.
Explore the Hydrocephalus Center, learn more about Pediatric Neurosurgery, or visit our New Jersey offices for appointment information.
Call (973) 326-9000 to ask about scheduling and the appropriate service for your family's needs.
