Fetal-maternal haemorrhage is the loss of fetal

blood cell A blood cell, also called a hematopoietic cell, hemocyte, or hematocyte, is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes) ...

s into the maternal circulation. It takes place in normal pregnancies as well as when there are obstetric or trauma related complications to pregnancy. Normally the maternal circulation and the fetal circulation are kept from direct contact with each other, with gas and nutrient exchange taking place across a membrane in the placenta made of two layers, the syncytiotrophoblast and the cytotrophoblast. Fetal-maternal haemorrhage occurs when this membrane ceases to function as a barrier and fetal cells may come in contact with and enter the maternal vessels in the decidua/endometrium.

Description

Normal pregnancy

It is estimated that less than 1ml of fetal blood is lost to the maternal circulation during normal labour in around 96% of normal deliveries. The loss of this small amount of blood may however be a sensitising event and stimulate antibody production to the foetal red blood cells, an example of which is Rhesus disease of the newborn.

Abnormal pregnancy

Causes of increased foetal-maternal haemorrhage are seen as a result of trauma, placental abruption or may be spontaneous with no cause found. Up to 30ml of foetal-maternal transfusion may take place with no significant signs or symptoms seen in either mother or

foetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal develo ...

. Loss in excess of this may result in significant morbidity and mortality to the fetus. Fetal-maternal haemorrhage is one cause of intrauterine death (IUD).

Diagnosis

The

Kleihauer–Betke test The Kleihauer–Betke ("KB") test, Kleihauer–Betke ("KB") stain, Kleihauer test or acid elution test is a blood test used to measure the amount of fetal hemoglobin transferred from a fetus to a mother's bloodstream. It is usually performed on ...

is a blood test used to measure the amount of foetal hemoglobin transferred from a foetus to its mother's

bloodstream The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

. It takes advantage of the differential resistance of foetal hemoglobin to acid. A standard

blood smear A blood smear, peripheral blood smear or blood film is a thin layer of blood smeared on a glass microscope slide and then stained in such a way as to allow the various blood cells to be examined microscopically. Blood smears are examined in the ...

is prepared from the mother's

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

, and exposed to an acid bath. This removes adult

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...

, but not foetal hemoglobin, from the red blood cells. Subsequent staining, using Shepard's method, makes fetal cells (containing foetal hemoglobin) appear rose-pink in color, while adult red blood cells are only seen as "ghosts". 2000 cells are counted under the microscope and a percentage of foetal to maternal cells is calculated. Fetal-maternal haemorrhage can also be diagnosed by flow cytometry, using anti-foetal hemoglobin antibodies (anti-HbF).

Treatment

If ongoing and rapid haemorrhage is occurring then immediate delivery of the foetus may be indicated if the fetus is sufficiently developed. If the haemorrhage has already occurred and now stopped, an inutero transfusion of red cells to the foetus may be recommended.Massive fetomaternal hemorrhage and oxytocin contraction test: case report and review Arch Gynecol Obstet. 2004 Jan; 269 (2):149-51 14648183 (P, S, G, E, B)

References

External links

{{Certain conditions originating in the perinatal period Health issues in pregnancy