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Fetal Anemia

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Fetal anemia is a complication of pregnancy where the fetus has lower levels of red blood cells, and hence the hemoglobin also goes below normal levels. Fetal anemia is a rare disorder but may cause serious adverse effects.

Fetal anemia refers to inadequate quality or number of red blood cells in the fetal blood system. Proper functioning of the circulatory system is important in a developing fetus; any disorder or deficiency in blood supply may lead to many complications. Though severe fetal anemia is rare, it can be risky for the baby and may cause abnormal fluid buildup in many regions of the body, heart failure, and sometimes even death.

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What are the causes of Fetal anemia?

Several factors are known to cause Fetal anemia, some of which includes:

  • Maternal alloimmunization: This is also known as isoimmunization. The presence of irregular antibodies (non-ABO antibodies) when the baby’s RBCs are not compatible with the mother’s RBCs increases the fetus’ risk of hemolytic disease.
  • Infections in pregnant women: During pregnancy, various viral, bacterial, and parasitic infections may cause fetal anemia. These include infections such as parvovirus, toxoplasmosis, cytomegalovirus (CMV), coxsackievirus, and syphilis.
  • Bleeding: Blood loss from the infant’s circulatory system may cause fetal anemia.
  • Underdeveloped organs: Any deformity or underdeveloped organs in the fetus, such as defects in the heart, may cause fetal anemia.
  • Nutrition deficiency: Iron deficiency, folate, and vitamin B12 deficiency in the pregnant mother may cause Fetal anemia.

Some other causes of fetal anemia include:

  • ● Genetic disorders- including Downs syndrome
  • ● Tumor in the blood vessel, lymph node with the vascular origin of the fetus.
  • ● Fetomaternal hemorrhage from maternal abdominal trauma resulting in placental abruption.
  • ● Twin anemia polycythemia sequence (TAPS). A condition where monochorionic twins (identical twins) share a common placenta. This may cause an imbalance in blood supply to the developing fetus leading to Fetal anemia.

What are the effects of fetal anemia on the mother?

The adverse effect in mothers with anemic fetus include:

  • ● Reduced resistance to infection caused by impaired cell-mediated immunity.
  • ● Reduced ability to withstand postpartum hemorrhage.

What are the effects of fetal anemia on the fetus?

The effects of fetal anemia on the developing fetus include:

  • ● Intrauterine hypoxia and growth retardation.
  • ● Prematurity – Low birth weight.
  • ● Increased risk of perinatal morbidity and mortality.

How is fetal anemia diagnosed?

During pregnancy, prenatal testing helps in the detection of fetal anemia. To diagnose fetal anemia, the doctor may ask to undergo the following tests:

  • Maternal blood testing for fetal abnormalities:

Maternal serum or blood tests can help diagnose fetal defects in women with an increased risk of having a baby with congenital disorders.

  • Amniocentesis:

Amniocentesis is a medical evaluation used as primary in prenatal diagnosis. The test involves the sampling of amniotic fluid surrounding the sac of the fetus. Various pathological and biological testings are performed on the amniotic fluid to diagnose congenital anomalies and fetal infections. Amniocentesis is often a risky procedure, so it is mostly recommended in women with an increased risk of having babies with congenital disabilities.

  • Fetal blood sampling tests:

Fetal blood sampling involves an analysis of blood from the unborn baby during pregnancy. Similar to amniocentesis, fetal blood sampling is also associated with higher risks.

How is fetal anemia treated?

Fetal anemia is monitored and treated prenatally by several methods. In mild cases, monitoring is enough to ensure until the anemia does not cause problems. If the anemia is moderate to severe, a fetal blood sampling and transfusion may be necessary for fetal anemia treatment. In most confirmed cases of fetal anemia, blood transfusion is recommended to compensate for fetal blood supply.

  • Intrauterine transfusion

An intrauterine transfusion is a procedure that provides blood to a fetus, most commonly through the umbilical cord. It is mostly used in severe fetal anemia cases, such as when maternal antibodies destroy fetal red blood cells. Fetal paralytic agents, such as rocuronium, atracurium, and vecuronium, are particularly useful if a prolonged or difficult procedure is anticipated.

  • Non-invasive management: Intravenous immunoglobulin (IVIG)

Intravenous immunoglobulin (IVIG) is a blood product prepared from the serum of between 1000 and 15,000 donors per batch. It is the treatment of choice for patients with antibody deficiencies. IVIG alone or in combination with plasmapheresis appears to improve fetal outcome and delay or decrease the need for perinatal blood transfusion.


In most fetal anemia cases, it is difficult to attribute the cause of fetal anemia to one single factor. It remains one of the major complications of pregnancy. Frequent monitoring of blood flow in the middle cerebral artery (MCA) in pregnant women can help in the early diagnosis of fetal anemia. Implementing dietary changes with iron-rich supplements may help to prevent further complications to the fetus. Blood transfusion is often recommended for severe confirmed cases of anemia in the fetus.

What are the risks of invasive intrauterine transfusion?

An IUT is typically only performed when the fetus is known or suspected to have life-threatening anemia. Complications and associated risks  of intrauterine transfusion include:

  • ● Fetal infection
  • ● Infection in the maternal uterus
  • ● Premature birth
  • ● Excessive hemorrhage
  • ● Mixing of maternal and fetal blood
  • ● Leakage of amniotic fluid from the uterus
  • ● Fetal mortality.

After intrauterine transfusion through the umbilical cord, fetal survival rates are more than 90% for fetuses that do not have hydrops and about 75% for fetuses that have hydrops.

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How Will you Classify Anemia?

Anemia is classified into four types based on the hemoglobin content in blood:

  • ● Mild case- (9-11 gm %)
  • ● Moderate case- (7-9 gm%)
  • ● Severe case-(4-7 gm%)
  • ● Very severe case-( <4%)

Mention Some Special Tests Used to Diagnose Fetal Anemia?

Serum folate, RBC folate, serum vitamin B12, Coombs test are some special tests used to diagnose Fetal Anemia.

What are Some Prophylactic Measures Taken for Fetal Anemia?

Routine screening of Anemia, encouraging iron-rich food, fortification of widely consumed food are some prophylactic measures.

What are Some Iron-Rich Foods?

Pulses, cereals, jaggery, beetroot, green leafy vegetables, etc.

What are the Adverse Effects of Blood Transfusion in Pregnant Females?

Transfusion reaction, infection, volume overload, citrate toxicity, etc.

What are the Factors that Increase Erythropoietin Secretion?

Hypoxia, androgens, growth hormones, prostaglandins can increase Erythropoietin secretion.


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