Fetal Anemia

Fetal anemia is when a fetus doesn’t have enough red blood cells or hemoglobin, which are needed to carry oxygen to organs and tissues. If the fetus’ tissues aren’t receiving enough oxygen, the heart will attempt to compensate and can become overworked, leading to heart failure, a condition where the heart can no longer pump blood effectively.

Fetal anemia may not cause noticeable signs or symptoms in its early stages. However, as it progresses, it can lead to complications such as decreased fetal movement.

Prenatal ultrasound may reveal the following findings:

• Changes in fetal heart rate
• Decreased fetal movement
• Hydrops fetalis
• Pregnancy loss (in severe cases)

Fetal anemia can be caused by several factors, including:

• Alloimmunization: When a pregnant person’s immune system creates antibodies against the fetus’ red blood cells due to blood type differences, it can lead to fetal anemia. For example, if the pregnant person is Rh-negative and the fetus is Rh-positive (known as Rh incompatibility), the immune system may attack the fetus’s red blood cells.
• Prenatal infections: Some viruses, such as parvovirus (fifth disease), can interfere with a fetus’ ability to produce red blood cells.
• Twin anemia polycythemia sequence (TAPS): A rare condition with identical, monochorionic twins, where abnormal, one-way blood flow between the twins through the placenta causes anemia in one twin.
• Inherited conditions: Conditions passed on from a biological parent, such as alpha thalassemia, can lead to fetal anemia.
• Fetomaternal hemorrhage: When fetal blood enters the maternal bloodstream during pregnancy or childbirth.
• Other less common structural anomalies in the fetus or placenta.

Pregnancies at risk for fetal anemia, or with early signs or symptoms, may be screened with a noninvasive prenatal ultrasound to measure blood flow in the fetus’ brain. This is called a middle cerebral artery Doppler measurement. A fetal echocardiogram can also help identify signs of fetal anemia.

Fetal anemia may be confirmed through a procedure called cordocentesis, where a blood sample is taken from the fetus using an ultrasound-guided needle. The blood sample is usually collected from the umbilical vein in the umbilical cord.

How fetal anemia is managed and treated depends on its underlying cause, severity, and the gestational age of the fetus.

Treating fetal anemia during pregnancy

Prenatal treatment of fetal anemia can include:

• Close monitoring with ultrasound to ensure fetal well-being.
• Intrauterine blood transfusion: A blood transfusion using ultrasound guidance injects blood into the umbilical cord or directly into the fetus’ abdomen.
• Early delivery: In some cases, if the anemia is severe and other treatments aren’t effective, an early delivery may be necessary.

Treating fetal anemia after birth

Depending on the severity of anemia and the gestational age at the time of birth, some infants will require admission to the Neonatal Intensive Care Unit (NICU) for close monitoring and to receive additional treatment. Common treatments for anemia after birth include:

• Blood transfusion: Depending on the severity of anemia, infants may need one or multiple blood transfusions after birth to replace red blood cells and improve oxygen delivery to organs and tissues.
• Oxygen therapy: An infant may require supplemental oxygen to help ensure their organs get enough oxygen while their red blood cell count recovers.
• Phototherapy: Depending on the cause of fetal anemia, some infants are at higher risk for developing hyperbilirubinemia (jaundice). Phototherapy (light therapy) may be needed to reduce bilirubin levels and treat jaundice.

Treatment for fetal anemia is customized to meet each infant’s unique clinical needs, with a focus on safely restoring red blood cell levels to support their overall health and development.

Long-term outcomes for infants with fetal anemia depend on the severity and timing of diagnosis and treatment. With early pre- and postnatal interventions, most infants are expected to recover fully and lead healthy lives. After treatment, close outpatient follow-up by the infant’s pediatrician is essential to monitor the hemoglobin levels, growth, and development.

Boston Children’s Fetal Care and Surgery Center provides comprehensive care for fetal anemia. Our team works closely with prenatal care providers as well as with maternal-fetal medicine specialists experienced in high-risk pregnancies and conditions such as fetal anemia. Our team includes experts in:

• Maternal-fetal medicine
• Fetal surgery
• Genetics and genetic counseling
• Neonatology
• Nursing
• Pediatric hematology
• Radiology and imaging

Our personalized care plans and specialized advanced treatments are designed to ensure the best possible outcomes for our patients. We work closely with patients and their existing care team to provide coordinated education, support, and a clear plan for managing fetal anemia before and after birth, including immediate access to our Level III/IV neonatal intensive care unit (NICU).