S was in her second trimester of pregnancy. She was worried when she noticed that her baby was moving less and less. Her baby’s heart had stopped when she came for antenatal review at 26 weeks of gestation. S, 30, was diagnosed as an alpha thalassemia carrier when she was found to be anemic at the age of 18. Her husband,32, also suffered from the same medical condition. During the preconception check, she was forewarned that there was a 25 percent chance that her baby could end up as a stillborn if the baby inherited both their genes.
What is thalassemia?
Thalassemia is an inherited blood disorder that causes the body to produce a reduced amount of hemoglobin, a protein in the red blood cells that carries oxygen and nutrients to the cells in the body. Hemoglobin molecules are made of two components called alpha and beta chains. The production of these chains is determined by the genes. Any genetic mutations or changes will affect their production. In thalassemia, the production of either the alpha or beta chains are affected, resulting in either alpha-thalassemia (AT) or beta-thalassemia (BT). Depending on the severity, thalassemia is further classified in two forms: minor and major.
How common is thalassemia in Singapore? In Singapore, about 3 to 9% of the population are carriers of the thalassemia gene. This means the risk of the child being born with thalassemia is much higher if both parents are carriers of the gene.
What is alpha thalassemia (AT)? Four genes are involved in making the alpha hemoglobin chain, two from each of the parents. Severity of AT depends on how many genetic changes occur. In the severe form, all the 4 genes undergo mutation. This will result in stillbirth as in the case of S.
What is beta-thalassemia (BT) Two genes are involved in making the beta hemoglobin chain. As in AT, if two genes undergo changes, symptoms of anemia will be severe.
What could be the fetal and maternal complications of alpha thalassemia major (ATM)? Foetal complications: Alpha Thalassemia Major (ATM) is the most severe form of AT, in which both parents pass the defective genes to the fetus. The fetus will suffer from severe anemia and die from heart failure with accumulation of excessive fluid around the heart, lungs, intestines, abdomen as well as the skin and placenta. The baby appears swollen all over and is called hydrops fetalis.
Maternal complications In severe ATM with hydrops fetalis, the mother may be at risk of maternal mirror syndrome, where the mother's condition mimics that of the sick fetus. The mother develops symptoms such as vomiting, hypertension, swelling of the hands and feet, passing protein in the urine and pulmonary edema (fluid in the lungs). The condition, though uncommon, may require delivering the fetus immediately.
Can ATM be diagnosed by prenatal tests? If both parents are carriers of AT, prenatal tests can be done during early pregnancy. They are: 1. Chorionic villus sampling (CVS): The placental tissues are sampled at 10 to 13 weeks of pregnancy for molecular testing.
2. Amniocentesis: Cells in the amniotic fluid are taken at 14 to 20 weeks of pregnancy for analysis.
S and her husband were referred for genetic counselling before conception. They were aware of the possibility of a negative pregnancy outcome. However, because of religious reasons, they opted not to do the prenatal test. After she was informed of her foetal demise, she decided to have the labour induced and delivered the hydropic baby weighing 1 kg.