Definition
The brain has fluid filled spaces called ventricles. If these spaces appear larger than expected on an ultrasound of an unborn baby, it is called ventriculomegaly. Doctors are not usually able to predict during pregnancy whether this enlargement will affect a baby later in life or not. Sometimes this enlargement resolves on its own during the pregnancy or after birth.
Causes
The ventricles in a fetus develop early in pregnancy and can be seen well by about 15 weeks. Enlargement of the ventricles may be caused by a blockage, an infection or another defect in the development of the brain. Doctors are not always able to find the cause during a pregnancy. It is not thought that ventriculomegaly is caused by anything a mother did or did not do during her pregnancy.
Care during pregnancy
It is usually recommended that a mother with this finding has an ultrasound with a high risk obstetrician (maternal fetal medicine) about every month to watch for changes and to learn more about the baby. The mother should also keep her appointments with her regular obstetrician. An amniocentesis (removal of a small amount of fluid from around the baby) might be recommended to check the baby’s chromosomes or to see if there is an infection. There is no other treatment needed during pregnancy for ventriculomegaly.
In some cases, the high risk obstetrician might want a patient to meet a pediatric neurosurgeon at Nationwide Children’s Hospital to talk about what care the baby might need after birth.
Ventriculomegaly can change during pregnancy. One study found that ventriculomegaly improved or disappeared during pregnancy in almost half of the cases. It stayed the same in over one third of the cases studied and got larger in 18 percent of the cases.
Ultrasound Measurements
Ultrasound measurements are estimates. Using ultrasound during pregnancy to take measurements and evaluate a baby can be challenging because of the baby’s position, the baby’s movements and the fact that the baby is within the mother. The normal size of the ventricles is usually considered to be less than 10 mm (millimeters). A difference of up to 2 mm might occur due to positioning, movement and other factors. Therefore, changes of 1-2 mm may not be considered significant by your doctor. While the other areas of the brain continue to grow larger along with the rest of the baby, the ventricles normally stay the same size throughout the rest of the pregnancy.
Magnetic Resonance Imaging
The high risk obstetrician might want to get pictures of the baby’s brain using another test called fetal MRI (magnetic resonance imaging). This test is done at Nationwide Children’s Hospital, where pediatric specialists will look at the images.
If the MRI does not find any other problems in the brain, the chances that the baby will have normal long-term development increases. Two studies of MRI performed for ventriculomegaly found that other abnormalities in the brain are identified in about 5 percent of cases. Usually the MRI does not change the way doctors care for the pregnancy or plan for the delivery. It is not routine to do a fetal MRI in all cases of ventriculomegaly.
Outcomes
Most parents want to know what this ultrasound finding might mean to their child’s future. Survival has been reported to be 95-98 percent if the baby has no other defects. A few studies have been done on the outcome of babies with ventriculomegaly (and no other abnormalities) during pregnancy. One study found that 85 percent of these babies had no neurological or developmental delays when they were 2 years of age or older. Another study found that 79 percent of babies did not have any developmental delays at 20 months of age. The remainder (15-21 percent) had mild or severe problems or delays in hearing, speech, vision, motor skills or learning. Some small studies suggest that developmental problems may be worse if the ventricles are extremely large and in babies who have other problems besides ventriculomegaly. To fully answer these questions, future researchers need to follow affected children for longer than 2 years.
After birth
Very importantly, babies with ventriculomegaly found during pregnancy should be seen by neurosurgeons or neurologists after birth. They will decide if any treatment is needed. After delivery, mothers should talk to their pediatrician to be sure this follow up is arranged.