What Is Hemolytic Disease of the Newborn (HDN)?
One of the scariest diagnoses for a mother and her unborn baby is a disease referred to as Hemolytic Disease of the Newborn (“HDN”), also known as “Anti-Kell.” Anti-Kell is a condition in which the antibodies in a pregnant woman’s blood cross the placenta and destroy her baby’s red blood cells. Red blood cells carry oxygen to all of the vital organs in our bodies. If the mother’s Kell antibodies begin attacking and destroying the baby’s red blood cells, this can lead to the baby becoming anemic and, more significantly, causing the vital organs to die. Fetal death can also occur.
First, some background and basics. As most mothers know, typically, around 17-20 weeks gestation, pregnant moms undergo a number of antenatal blood screening tests that are designed to test for a wide range of potentially harmful conditions to the baby. One of those blood tests, called an Indirect Coombs Test (“ICT”) looks for the presence of what are known as Kell antibodies on the mother’s red blood cells. Antibodies are molecules that are produced by the cells of the body’s immune system. Antibodies have the ability to recognize bacteria and viruses by attaching to what are known as “antigens” on the surface of other cells. The immune system only makes antibodies for a specific antigen if it encounters that antigen during its surveillance of the body. Kell antibodies, for example, bind to Kell antigens on red blood cells. Kell antibodies are usually made by the mom’s body after the mom has undergone a prior blood transfusion in which new blood contains the Kell antigen that is not the mother’s own. So, essentially, the mother, who was Kell negative (no anti-bodies) becomes Kell positive after being exposed to blood that has the Kell antigen. Simply having the Kell antibody (for moms) is not unusual or harmful. When antibodies are found on the mother’s red blood cells, the mother is referred to as being “Kell positive.”
What Does It Mean to Be Kell Positive or Kell Negative?
If a mother is found to be Kell positive, the number of antibodies present is determined through the same testing and the mother is given a “score.” This score is referred to as a titer. Titers of 1:8 or higher are considered critical for Kell. Once a critical titer is reached, vigilant monitoring by the mother’s obstetrician, or more usually, maternal fetal medicine (“MFM”) specialist, is required. Failure to do so constitutes negligence.
Roughly 90% of the population (males and females) are Kell negative, meaning they don’t have the antibodies, while 10% are Kell positive. Accordingly, there is a high likelihood that when a mother and father conceive a child, that fetus will be Kell negative. If, however, the mother and father are mis-matched in terms of Kell positivity/negativity, then there exists the chance that the mother could be Kell positive (antibody present) and the baby could be Kell negative (antibody not present). When this happens, the fetus is at risk for developing Hemolytic Disease of the Newborn if the mother’s blood containing the antibody crosses the placenta and starts to destroy the baby’s red blood cells.
How to Determine if a Fetus is at Risk for HDN/Kell
As noted above, step one in determining if a fetus is at risk for HDN/Kell is to determine whether the mother is Kell positive through the Indirect Coombs Test at approximately 17-20 weeks gestation. If the mother tests positive, step two is to determine whether the father possesses the Kell antigen. If the father is what is known as homozygous (his paired genes are +/+) for the antigen, there is a 100% chance the fetus of the pairing will be positive for the Kell antigen and at risk for HDN. If, however, the father is heterozygous (his paired genes are +/-) for the antigen, there is only a 50% chance of the fetus being positive for the antigen.
Regardless of the risk level (100% vs. 50%), if the mother is found to be Kell positive (with the antibody) and her titer score is above 1:8, the standard of care requires the mother’s OB or MFM specialist to closely monitor the baby’s condition. This is accomplished primarily through the use of what is known as a Middle Cerebral Artery ultrasound. This is a non-invasive test that measures the peak velocity of the fetus’ blood in the middle cerebral artery in the brain. If the velocity of the blood in the middle cerebral artery is above a certain threshold, this indicates the presence of anemia, and very likely, HDN. The standard of care requires that the mother’s doctors frequently measure the MCA blood velocity, usually every week or every two weeks (following 20 weeks) to ensure that the fetus’ anemia does not become severe.
In addition to monitoring the MCA blood velocity, doctors also must carefully monitor the fetus for the development of a condition known as hydrops fetalis, a serious fetal condition defined as abnormal accumulation of fluid around various organs. The accumulation of fluid is a direct result of the loss of red blood cells and reflects the body’s attempt to combat the lost red blood cells.
If the fetus’s anemia (or hydrops) becomes severe, the standard of care typically requires that mom and baby undergo what are known as intrauterine transfusions wherein the fetus receives additional red blood cells to help combat the loss of red blood cells caused by the mother’s antibodies. The infusion of “good” red blood cells can help preserve normal organ function and lung development while simultaneously avoiding accumulation of fluid around organs (hydrops fetalis).
Birth Injuries and Risks Associated with Anti-Kell/HDN
The biggest risk associated with Anti Kell and Hemolytic Disease of the Newborn is the premature delivery of the fetus. If the fetus is not monitored closely for the development of anemia, hydrops fetalis and HDN, often times the baby is born prematurely with severe anemia and organ compromise. As a result, these children can spend years in the hospital battling for their lives. Once out of the hospital, these children are routinely beset with complications stemming from their organ compromise (i.e., heart, lung, liver, kidney dysfunction). Caring for these children is often financially devastating for their parents as they can often require round-the-clock care and the vigilance of many specialists. For all of these reasons, if you or a loved one who is pregnant have been found to be Kell positive with a critical titer, it is paramount that your OB or MFM specialist begin vigilant monitoring of your unborn child between 17-20 weeks gestation. Failure to do so not only falls below the standard of care, i.e., is negligent, but can also result in devastating injuries and permanent deficits for your child.
Our Baltimore Birth Injury Lawyers at Bennett & Heyman Offer Free Consultations
At Bennett & Heyman, our medical malpractice lawyers have experience in handling cases in which it is alleged that a pregnant woman’s obstetrician and maternal medicine specialist were aware of the presence of maternal anti-Kell antibodies and failed to closely monitor the fetus through the use of serial MCA ultrasounds. If this has happened to you or a loved, call our team of Baltimore birth injury attorneys for a free consultation regardless of where the negligence took place. Our team can help your child and your family secure the support you need and deserve.