How late in pregnancy can hemolysis be detected in women with type O blood?

When the pregnant woman has blood type O, hemolytic disease testing should be performed no later than around 30 weeks of gestation to ensure timely detection and prevention of ABO hemolytic disease. ABO hemolysis mainly occurs when the mother has blood type O and the fetus has blood type A or B. Because the mother may produce anti-A or anti-B antibodies, these antibodies can cross the placenta and enter the fetal circulation, causing hemolysis. Hemolytic disease testing is usually performed initially at approximately 16 weeks of gestation, followed by a repeat test at 28–30 weeks to monitor changes in antibody titers. If antibody titers continue to rise, further measures may be necessary to reduce the risk of hemolysis. In addition, pregnant women should undergo regular prenatal examinations throughout pregnancy to monitor fetal growth and development. Although ABO hemolytic disease is uncommon during pregnancy and symptoms are typically mild, timely testing and intervention are crucial for ensuring maternal and fetal health. Therefore, it is recommended that pregnant women with blood type O undergo hemolytic disease testing at the appropriate time during pregnancy and take necessary preventive measures according to medical advice.