Anti-Vel is an uncommon antibody to a high-prevalence antigen. Its clinical 
significance and management in the prenatal setting are not well characterized. 
We present a case that demonstrates the utility of serial prenatal anti-Vel 
quantitative serologic monitoring with 2-ME serum treatment during pregnancy. 
The patient is a 23-year-old Hispanic woman with history of prior pregnancy and 
prior transfusion who was discovered to have an antibody to the high-prevalence 
Vel antigen in the first trimester (week 7) of her second pregnancy. Interval 
measurements of the serologic antibody titers were performed during the next 26 
weeks. The untreated serum (IgM and IgG) titer increased from a baseline of 4 to 
16 during that interval, while the 2-ME (presumed IgG component) titer remained 
stable at 4. Responding to ultrasound findings suspicious for fetal anemia, the 
child was delivered without complications at 34 weeks' gestation. At birth, the 
DAT was negative and there was no evidence of HDN. Placed in the context of 
other similar reports, this case demonstrates the importance of separately 
reporting the IgG fraction (after either DTT treatment or 2-ME treatment) from 
the untreated (IgM and IgG) fraction and the importance of correlating the 
treated serum titer with potential clinical significance.