Excessive fluid buildup around the heart, known as pericardial effusion, can be diagnosed on fetal ultrasound. Pericardial effusion can interfere with the heart's ability to pump blood to the rest of the body. The fetus doesn't receive enough oxygen to grow properly and may die before birth. A number of conditions can cause accumulation of fluid around the fetal heart.
Rh Disease
The Rh factor is a protein found on red blood cells in 85 percent of people who are said to be Rh-positive. Rh disease develops in an Rh-positive fetus whose mother is Rh-negative. Rh disease doesn't develop until a woman has had at least one pregnancy. Fetal blood cells cross the placenta in small amounts and cause the mother to develop antibodies which attack the abnormal blood cells. In subsequent pregnancies, the antibodies cross the placenta and attack the blood of an Rh-positive fetus. Red blood cells are destroyed and the fetus becomes severely anemic. The fetus retains fluid, or edema, which may occur around the heart.
Pericardial effusion may be visible on ultrasound when the fetal hemoglobin drops seven grams per deciliter below the normal levels for gestational age of the fetus, the University of New Mexico states.
Twin to Twin Transfusion Syndrome
Twin to twin transfusion syndrome, also called TTTS, affects only identical twins, especially those who share the same amniotic sac. Identical twins, who develop from the same embryo, share a placenta. As blood circulates through the placenta, one twin may end up with too much blood circulating and the other may not have enough blood 5 to 15 percent of the time. Both twins may develop heart failure, but for different reasons, according to the Warren Alpert Medical School at Brown University.
Other Causes
Several other conditions can cause fluid accumulation around the heart in a fetus. Fetal heart failure leads to pericardial effusion, states James Huhta, MD, of the University of South Florida College of Medicine. Congenital heart disease and heart arrhythmias may cause fluid accumulation, cystic hygroma, cysts that form from embryonic lymph tissue, infection and diaphragmatic hernia, an abnormal opening between the abdomen and chest cavity, can also lead to pericardial effusion, according to Dr. Huhta. Pericardial effusion on ultrasound may also indicate an increased risk of Down syndrome in a fetus, says Dr. Greggory DeVore, MD, of the Fetal Diagnostic Centers.
