This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Two weeks later, the results of the patient's prenatal labs come back. Her blood type is A, with an anti 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: In the same patient–blood grouping shows A negative, with an anti D antibody titer of 1:4- the most appropriate next step
in the management –Since this patient is a primi patient and her antibody titre is 1:4 so we should follow it by doing a repeat titre after every 4 weeks.
If this pregnancy would not have been her first affected pregnancy, then amniocentesis i.e. option a would have been the correct response.