The Brain:
Ventriculomegaly

This is where the ventricles, which are part of the baby’s brain, measure larger than normal. The cut off for normal is 10mm. This is what we call a ‘soft sign’ and may indicate a problem with the baby due to one or more of many causes, or it may be the only abnormality in which case it is termed isolated ventriculomegaly.

The doctors need to exclude many different things that can cause this including infections, structural problems where the brain has not formed properly and, sometimes, genetic problems.

Fetal MRI is done to look at the structure of the baby’s brain. It will look at the individual components and also check how well the brain is forming and developing to make sure this is what we expect for the number of weeks your pregnancy is at.

The outcome or prognosis for your baby depends on what the results of the different tests show.

Isolated mild (less than 15mm) ventriculomegaly has a good outcome. 85% or more of these babies have developed normally by the time they start school. A small percentage will need help at school but still attend mainstream school.

This is where the bridge of tissue that connects the 2 halves of the brain has not formed. This may be the only finding (isolated) or it may be associated with other abnormalities. Some of the other abnormalities can develop during the rest of the pregnancy so there is always a small risk of other abnormalities developing.

The outcome for your baby depends on what else, if anything develops and what is there at the time of the first scan.

In Sheffield we offer a second MRI scan at 32 weeks to have a further look at the development of the brain.

In females this can be part of a genetic condition- Aicardi syndrome.

A very helpful support group is CORPAL.

The Brain:
Arachnoid cysts

These are collections of fluid in between two membranes covering the brain. They may displace the brain but do not usually damage the brain. Occasionally they can compress an area that causes a block in the flow of the fluid (CSF) around the brain and this may cause additional problems. These can shrink in size and are usually monitored with regular ultrasounds during pregnancy and with other imaging techniques after the baby is born.

The Spine:
Spina bifida

This is where there is a gap in the spine on the back of the baby so that the nervous tissue is exposed. It may be open or it may have a covering. This can occur anywhere down the spine from the neck to the base of the spine.

It is often associated with changes in the brain termed Chairi II malformation where there is little fluid around the brain and the base of the brain is lower than normal and sits in the spinal canal in the upper neck region. This can then cause the ventricles in the brain to become dilated (larger than normal) because the normal flow of fluid around the brain and spine is blocked.

These cases are all different and the outcome is dependent on the position of the gap, the amount of nervous tissue involved, the covering, if any, over the exposed nervous tissue and other factors.

The fetal MRI will provide additional information to the ultrasound scan. All the information will be used by the doctors looking after you to help give you information on what is likely to happen after birth of the baby and what the outlook is for your baby.

A really helpful group is SHINE.

The most common lesions are cystic malformations or congenital diaphragmatic hernias.

Cystic malformations cause the area of the lung affected to be brighter and bigger. The expansion of this area may cause displacement of the heart and vessels towards the opposite side of the babies chest.

In general these lesions tend to increase in size until 28 weeks gestation and then start to decrease in size. The outcome for the baby is very good. The pregnancy will be monitored with ultrasound after fetal MRI has confirmed the diagnosis. The baby will have a CT scan at around 6 weeks of age and may have the cysts removed around the age of 1 year.

Rarely the cysts may be large and the area involved very big so that is puts pressure on the heart and this can cause a build up of fluid in the baby. This is why the pregnancy will be monitored with ultrasound so the doctors can pick this up early and decide how to manage the pregnancy.

Occasionally we see isolated cysts in the lungs that may be from several different causes, the outcome depends on what is causing the cyst but is generally good.

This is caused by a hole in the diaphragm, which separates the chest from the abdomen. This allows the abdominal contents to go up into the chest and squash the lungs.

The outlook for the baby depends on how much of the lung is squashed and what has gone up into the chest cavity.

Fetal MRI can identify the organs more easily than ultrasound and allows the doctors to measure the amount of normal lung and see where the different organs are situated. The outlook depends on the amount of lung and where the organs are. Even when we have those details some babies do better than we expect and others do worse. The information from the fetal MRI will be used alongside that from the ultrasound and any additional tests, for example, chromosomes, to help the doctors give you an idea of what is likely to happen.

CDH UK is a helpful link.

The Kidneys:
Obstruction to the flow of urine

Sometimes the flow of urine from the kidney and down the tube that connects the kidney to the bladder and finally out of the bladder may be blocked somewhere along the way. This causes fluid to build up in the bladder, the tubes (ureters) or the kidney. If this gets too much it can damage the kidney. This can be seen on fetal MRI and an idea of the area of the block. It will be monitored during the pregnancy by regular ultrasounds and if necessary may require draining whilst pregnant, if possible. This depends on the site of the block and the impact it is having on the kidney. Your doctors will discuss this with you.