Fetal hemoglobin is a type of protein found in a baby’s blood before birth that carries oxygen from the mother’s bloodstream to the developing fetus. Also called hemoglobin F, fetal hemoglobin plays an essential role in early fetal development.
Fetal hemoglobin levels are also important when determining the severity of Hemolytic Disease of the Fetus and Newborn (HDFN), a condition in which the mother’s immune system produces antibodies that attack the baby’s red blood cells.
Understanding what fetal hemoglobin is, how it’s measured and its role in HDFN can help new parents better navigate this condition.
What is fetal hemoglobin?
Hemoglobin is the protein in red blood cells responsible for transporting oxygen throughout the body. Adult hemoglobin is called hemoglobin A, but developing babies in the womb have a different type of hemoglobin called fetal hemoglobin.
Fetal hemoglobin binds to oxygen more tightly than adult hemoglobin, making the transfer of oxygen from mother to baby easier and more efficient.
Shortly after birth, a baby’s red blood cell production shifts to making hemoglobin A, and fetal hemoglobin levels begin to decline. By six to 12 months of age, most infants have fully replaced fetal hemoglobin with adult hemoglobin.
How is fetal hemoglobin measured?
Fetal hemoglobin (HbF) levels can be measured using several methods. In newborns, it’s often detected through blood tests like high-performance liquid chromatography (HPLC), capillary electrophoresis and hemoglobin electrophoresis. These tests are typically used when a blood disorder is suspected.
In cases of HDFN, tests like the Kleihauer-Betke test and flow cytometry help measure the amount of fetal red blood cells that have entered the mother’s blood. This is known as fetomaternal hemorrhage. The amount of fetal hemoglobin in the mother’s blood helps doctors determine the severity of HDFN and what potential treatments may be needed.
Learn more about HDFN treatment and care
Why does fetal hemoglobin matter in HDFN?
HDFN occurs when the mother’s immune system attacks the fetus’s red blood cells, mistaking them for foreign invaders.
Measuring fetal hemoglobin helps doctors assess how much fetal blood is circulating in the mother’s blood. The amount can range from insignificant to severe, causing potential complications like fetal anemia and even death of the baby.
The results can help doctors determine if interventions, such as intravenous immunoglobulin, intrauterine transfusion or early delivery are necessary.
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