Immune Hydrops - Part Two
In the last post, we were following Janie's pregnancy. When we left off, Janie had a rising level of a dangerous antibody called Kell, and her fetus was showing signs of becoming anemic - on ultrasound, blood was flowing faster through the arteries in his brain.
Diagnosing HDFN
Fetal blood cells were being destroyed by maternal antibodies. This is a condition called hemolytic disease of the fetus and newborn (HDFN). HDFN is life-threatening for babies, and can even endanger the pregnant mom.
When HDFN is diagnosed, evaluation and treatment are urgent. A procedure called cordocentesis is performed. This is an amniocentesis (a needle placed into the sac of fluid around the baby), but instead of collecting amniotic fluid, the needle is advanced further into the fetus' umbilical cord.
A small sample of fetal blood is collected, to test the baby's blood count. If the baby is significantly anemic, a blood transfusion can be given directly through the umbilical cord. When these transfusions are performed, the donor blood is carefully screened for the protein that caused the original problem. In Janie's case, Kell-negative blood was given.
Treatment paths
The fetal transfusion (called intrauterine transfusion, or IUT) procedure can only be performed after about 18 weeks of pregnancy - prior to that age, the umbilical cord is not big or sturdy enough for blood collection and transfusion. And the procedure itself carries some risk to the baby. There is a possibility of a blood clot forming in the cord, or bleeding from the cord, or infection developing inside the uterus or rupturing the sac of fluid altogether.
When cordocentesis is performed for HDFN, transfusions frequently need to be done multiple times. The fetus may require transfusions once or twice a week until its blood volume is almost completely replaced with transfused blood. The transfused blood, remember, is negative for the protein that caused mom's antibodies to go crazy. Now that there is no Kell protein for mom to react to, the process can settle down.
In Janie's case, the cordocentesis was scheduled, but even before the procedure was performed the fetus developed hydrops.
Causes of hydrops
Now, finally, we get to the subject of hydrops. Hydrops fetalis is defined simply as an abnormal fluid collection in two or more compartments of the pregnancy.
For example, we may see extra fluid collected in the baby's abdomen (called ascites); or there may be fluid in the sac around the heart or lungs (pericardial or pleural effusions), or swelling in the skin and soft tissues, or extra fluid in the sac around the baby, or even swelling of the placenta.
Hydrops can be caused by antibodies that lead to fetal anemia, as in Janie's fetus, or it can be caused by viral infections or birth defects that affect the fetus' ability to move blood and fluids around. Sometimes, hydrops can result from a heart rhythm disturbance (arrhythmia).
How to approach treatment
Treatment of hydrops depends on the underlying cause.
With fetal anemia, the treatment is blood transfusions. If hydrops is caused by a fetal arrhythmia, this can also be treated during pregnancy, by giving mom anti-arrhythmic medications that cross the placenta and treat the arrhythmia. If hydrops is caused by a viral infection or a fetal anomaly, there may be no treatment at all except watching the fetus carefully with ultrasounds.
Since hydrops is a very dangerous and life-threatening condition for the fetus, preterm delivery may be indicated if the point is reached when the risk of fetal death outweighs the risk of prematurity.
Complications
Another potential complication that can accompany fetal hydrops is called the "maternal mirror syndrome." When this happens, the mom who is pregnant with a hydropic fetus also begins to swell. Severe swelling can develop, along with high blood pressure, protein in the urine, and fluid in mom's lungs.
This happens in only a few moms with hydropic fetuses, but when it does happen, the risk of fetal death can be as high as 50%, and delivery needs to take place promptly. Mom's swelling usually subsides within 1-2 weeks of delivery.
Janie's treatment
Janie's baby developed hydrops very quickly - within a few days of the abnormal cerebral blood flow being seen. There was fluid in the fetus' abdomen, and the skin and soft tissue appeared swollen.
She underwent several cordocentesis procedures and intrauterine transfusions. After the second transfusion, the fetal hydrops improved, and after the third transfusion, the hydrops resolved completely. Janie had ultrasounds twice weekly for the remainder of the pregnancy, and the baby was delivered at 35 weeks when we noticed reduced fetal activity and changes in the fetal heart rate tracing.
Her newborn son was mildly anemic, and this was treated with blood transfusions. His bilirubin level was elevated, and he became jaundiced. This is pretty common in babies who have had a destruction of their blood cells. He received phototherapy (ultraviolet light) and went on to do very well.
Future pregnancies
The recurrence risk for HDFN is very high. Remember, if the future fetus is positive for the offending protein, the maternal antibody response becomes quicker and more dangerous with each subsequent pregnancy.
I counseled Janie that future pregnancies with her boyfriend could be disastrous. There are options, though, that can reduce that risk dramatically. For instance, if we know that hydrops occurred due to blood group alloimmunization, Janie could consult with a reproductive endocrinologist. With in vitro fertilization, a fertilized embryo can be screened for Kell, and only embryos who are negative for the Kell protein would be implanted.
Another option would be to use donor sperm which has been screened for Kell. If hydrops occurred due to a fetal arrhythmia or viral infection, the recurrence risk may be very low, and no further planning may be needed for a future pregnancy.
Key takeaways from Janie's story
Whew, that was a long story to explain a really complicated process. The key points are:
If mom has a positive antibody screen during the pregnancy, she will need close surveillance to monitor for signs of fetal anemia and hydrops.
Only 10% of hydrops is due to antibody problems. This is called "immune hydrops." The other 90% develops due to other problems (infections, birth defects, heart problems, etc). This is "non-immune hydrops."
Hydrops can develop without warning, in a pregnancy that was previously uncomplicated. When this happens, we try our best to determine the cause, so that we can decide how best to care for mom and baby. A detailed ultrasound will be done. Amniocentesis may be recommended to look for infection, fetal chromosomes, and various genetic abnormalities. Blood work and antibody testing for mom may also be done.
In conclusion
Armed with everything that you know now, I hope that you will be prepared to ask questions about how your baby will be monitored and how you yourself will be watched in the event that your fetus develops signs of hydrops.