Definition
In prenatal diagnostics, the hydrops fetalis is described as an accumulation of fluid in the fetus. The fluid is found in at least two compartments of the fetus. The edema can spread over large parts of the unborn child’s body. The probability of a Hydrops fetalis is 1:1500 to 1:4000. Since the suspicion of a fluid accumulation in the child is an indication of a chromosomal change, a malformation of the organs or a severe disease of the fetus, it should be considered as a warning sign in ultrasound.
Causes of a fetal hydrops
The most common cause of fetal hydrops is anemia of the unborn child (fetal anemia). This can be caused by a rhesus incompatibility between mother and child. The rhesus-negative mother forms antibodies against the red blood cells (erythrocytes) of a rhesus-positive fetus.
However, the mother was sensitized earlier either in a previous pregnancy, by abortion or blood transfusion. Eventually, massive damage to the fetal red blood cells occurs, resulting in anemia of the unborn child. Among the rarer immunological causes are the fetofetal transfusion syndrome and thalassemia.
Non-immunological causes, which frequently cause fetal anemia, include congenital malformations of the heart. An increase in cardiac output may lead to heart failure and increased fluid retention. In addition, infections with toxoplasmosis, syphilis connata, rubella or cytomegalovirus are also among the causes of anemia and thus of fetal hydrops. Hydrops fetalis occurs more frequently in chromosomal diseases such as Turner syndrome, trisomy 18 or Down syndrome.
Diagnosis
Hydrops fetalis is usually diagnosed during a preventive ultrasound examination. The accumulation of fluid can be seen in the form of a lifting of the skin from the child’s body. If the mother has risk factors for the development of fetal anemia, regular ultrasound examinations should be performed during pregnancy.
In this way the pregnancy can be monitored and possibly the development of a fetal hydrops can be prevented. Anemia of the child can also be diagnosed by taking blood from the umbilical cord. If a heart defect is suspected, it can be examined by means of an ultrasound examination of the heart (echocardiography).
