The amount of ventricular dilation is consistent with hydrocephalus, although the cause is often difficult to determine prior to birth. Some causes of congenital hydrocephalus include infection, developmental abnormalities of the brain, genetic syndromes, and restrictions to the normal cerebrospinal fluid (CSF) flow within the brain and/or spinal cord (this is not an exhaustive list).
Depending upon the underlying cause, many babies with hydrocephalus can continue in the pregnancy until close to a term delivery. You will need to speak with your Obstetrician about a delivery plan depending upon the size of the head at that time.
Further evaluation of the hydrocephalus during the pregnancy will give you and your doctors information about the progression of the hydrocephalus. Depending upon the evolution of the hydrocephalus, you may want to discuss further plans for care after the baby is born. Depending upon the institution/group in which you are receiving care, it may be possible to obtain other consultations, including Neonatology, Pediatric Neurology, Pediatric Neurosurgery, and possibly Palliative Care services.
The care plan for your baby will depend upon the evolution of the hydrocephalus, the discussions you have with your doctors, and your own values and beliefs. There is no "best" approach to this as each baby and family will have a unique set of circumstances.