In order to determine the severity of a fetus's condition it is important to gather information from a variety of tests and determine if there are any additional problems. These tests along with expert guidance are important for you to make the best decision about the proper treatment.
1. The type of defect—distinguishing it from other similar appearing problems.
2. The severity of the defect—is your fetus’s defect mild or severe.
3. Associated defects—is there another problem or a cluster of problems (syndrome).
Amniocentesis may be necessary for chromosome testing. Sonography is the best imaging tool, but is dependent on the experience and expertise of the operator. Magnetic resonance imaging (MRI) may be necessary in some cases. Many problems are first detected during routine screening procedures performed in your doctor’s office (amniocentesis, maternal serum screening, routine sonography). However a through assessment usually requires a tertiary perinatal/neonatal center with experience managing complex and rare fetal problems.
Fortunately, it is possible to now predict before birth how good or bad your fetus’s CDH is. Careful and accurate prenatal assessment [level II sonogram, echocardiogram, sometimes magnetic resonance imaging (MRI) is critical for your decision-making and planning. One of the most important issues is to make sure there are no other birth defects (like heart problems) that will affect outcome.
Major Factors in Determining Severity
When CDH is the only problem, we have learned that severity and, thus, outcome is determined by two factors: 1) liver position, and 2) lung-to-head ratio or LHR. Liver position refers to whether or not any portion of the liver has herniated, or gone up into the chest of the fetus. Fetuses with the liver up in the chest have a more severe form of CDH and a low survival rate. About 75% of all CDH patients have some portion of the liver herniated into the chest. The lung-to-head ratio, or LHR, is a numeric estimate of the size of the fetal lungs, based on measurement of the amount of visible lung. High LHR values are associated with a good outcome.
Fetuses on the best end of the spectrum do not have liver herniated into the chest (liver down) and have a high lung-to-head ratio LHR greater than 1.4, indicating a relatively large lung. Through experience in evaluating many hundreds of CDH patients, about 25% are on the best end of the spectrum (liver down and/or high LHR greater than 1.4), and they all do well after birth. It is recommend that these babies be delivered normally near term in a center with a very good intensive care nursery and good pediatric surgery.
Fetuses with liver herniated into the chest and a lung-head ratio less than 1.0 are on the worst end of the spectrum. It can be sure that they will have a very difficult time after birth. Most can be helped with very high level intensive care, including ECMO. However, the very intensive care required for the most severe cases can lead to complications and long-term problems, including breathing and feeding difficulties for many years. In our experience, about 25% of fetuses have this severe form of CDH, and about 70% of these survive with very intensive management, but often with some handicap.
About half of all fetuses with CDH are neither very good nor very bad, but are somewhere in the middle of this spectrum. With good intensive care and surgery at an experienced medical center, most (more than 90%) will survive and do quite well.