What are Cystic Hygromas?
Cystic Hygromas are solitary or multiple cystic growths that tend to be seen mainly at the head or neck of a child. These cysts tend to grow larger as the baby grows. Cystic Hygroma start to form before the birth of the child and is visible about a year after the birth of the child. These cysts form due to blockage of vessels present in the lymphatic system of the body, especially in the area of the head and neck. 
The function of the lymphatic system is to transport WBCs and vital fluids through the body. The cysts seen in Cystic Hygroma normally form during the second trimester of the pregnancy. It has also been noted that majority of children with Cystic Hygroma have some form of chromosomal abnormalities. 
Cystic Hygroma is a relatively benign condition; however, it has the potential to cause some serious medical conditions like increased risk of a miscarriage. Thus most gynecologists recommended increased care and precaution in pregnant females carrying a child with Cystic Hygroma. 
What Causes Cystic Hygroma?
As to the causes of Cystic Hygroma, certain genetic abnormalities in most cases are the cause of this condition. There are also certain environmental factors which also play a role in the development of Cystic Hygroma.
Some of the environmental factors which cause Cystic Hygroma are certain viral infections in the mother that gets passed on to the unborn baby. Females who abuse alcohol and recreational drugs when pregnant also increase the risk of their baby having Cystic Hygroma. 
Some of the genetic conditions which tend to result in Cystic Hygroma include Turner Syndrome, Trisomy 13, and Noonan syndrome, all of which have gene or chromosomal abnormalities.
What are the Symptoms of Cystic Hygroma?
At the time of birth, the cysts from Cystic Hygroma are too small to be noticeable but as the child grows they start becoming visible and are most prominent by the time the child is around 1-2 years of age. 
The main presenting symptom of cystic hygroma is a soft compressible lump usually in the neck and head regions. In some cases, these lumps can be seen in the groin and in the armpits.
The cysts keep growing as the child grows and may become the size of a golf ball. If treatment is not sought and the cyst keeps growing then it tends to cause difficulties for the child to move the neck and surrounding areas of the body. 
How is Cystic Hygroma diagnosed?
A routine ultrasound done during second trimester of pregnancy may show signs of a Cystic Hygroma. If seen the physician may order an analysis of the amniotic fluid through amniocentesis. This may give the physician a fair idea of any genetic condition at play here.
In case, if the parents of a child are carriers of the defective gene that causes Cystic Hygroma and the tests mentioned above do not show any signs of the disease then a CT scan, x-ray or a repeat ultrasound of the head and neck can be performed after the birth of the child to rule in or rule out the disease. 
How is Cystic Hygroma Treated?
There is no way to treat Cystic Hygroma before the birth of the baby. The physician will opt for close monitoring looking for any signs of complications. There have been mild cases of Cystic Hygromas where the condition resolves by itself even before the baby is born. However, the delivery of the baby becomes critical if the cystic hygroma is found to be severe or if there is a major genetic disorder in the child.
In such cases, the timing and place of the delivery of the child becomes important and is often decided by the treating physician. Cystic Hygroma found in its early stages is definitely treatable. The frontline treatment for this condition is surgery to remove the growth in its entirety. This will ensure that it does not recur again.
In some cases the physicians refrain from removing extremely large growths. This is usually to prevent any injury to the adjoining structures at the time of surgery and moreover cystic hygromas are benign growths and pose no threat whatsoever.
They may use other forms of treatment to reduce the size of the growths like sclerotherapy in which the cyst is injected with medications which decreases its size. In rare cases radiation and chemotherapy can also be done to shrink the size of the growth. These are generally done to treat very large growths which are quite unsightly especially if they occur on the exposed part of the neck. 
What Is The Overall Prognosis Of Cystic Hygroma?
The overall prognosis of children with Cystic Hygromas is quite good. In some cases these children may have recurrence of the condition once the cyst is removed surgically. There is also a risk of bleeding and infection during or after surgery.
As is adherent to any surgical procedure, injury to the adjoining nerves and vessels during the time of surgery is also one of the risks that one has to keep in mind when undergoing treatment for Cystic Hygroma. In general, if the hygromas develop after birth there is a high likelihood of complete removal of the growth with little chance of recurrence.