This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Medical, surgical and gynaecological illness complicating pregnancy, Subject name: Gynaecology & Obstetrics
Two weeks later, the results of the patient&;s prenatal labs come back. Her blood type is A, with an antl D antibody titer of 1:4. What Is the most appropriate next step In the management of this patient? 
Select and explain. 
A. Schedule an amniocentesis for amniotic fluid bilirubin at 16 weeks, B. Repeat titer in 4 weeks, C. Repeat titer in 28 weeks, D. Schedule PUBS to determine fetal hematocrit at 20 weeks
B: Repeat titer in 4 weeks
Answer: B: Repeat titer in 4 weeks 
Explanation: Indirect coomb&;s test If the ICT is positive it should be repeated in dilution to find the Antibody titre.The critical titre for anti D antibodies is 1:16.If the titre is less than 1:16 it may be repeated 2 weekly.It is possible to do a immunoassay for anti D antibodies.The safe level is <4IU/ml.This is useful only in first sensitised pregnancy TEXTBOOK OF OBSTETRICS, SHEILA BALAKRISHNAN ,Pg no:311,2nd edition