over the background rate med.

[vitatel]

не пойму фразы, указанной в теме, в таком контексте:
However, the study was only able to exclude a 3- to 4-fold increased risk of congenital anomalies over the background rate. In 89% of these cases, drug treatment was initiated prior to pregnancy and was discontinued during the first trimester when pregnancy was identified.
подскажите, пож, кто разобрался

[qp]

over the background rate -- по сравнению с исходными данными/ по сравнению с исходным коэффициентом заболеваемости?

[vitatel]

да, согласна, спасибо!