The rosette test will detect a fetomaternal hemorrhage (FMH) as small as:

The rosette test is designed specifically to detect fetomaternal hemorrhage (FMH) and is particularly sensitive to small amounts of fetal cells in maternal circulation. This test utilizes anti-D (Rh) antibodies that bind to any Rh-positive fetal red blood cells present in the maternal blood, forming rosettes.

The sensitivity of the rosette test allows it to identify even very small volumes of FMH. In this context, the test can reliably detect as little as 10 mL of fetal blood in the maternal circulation. This makes it an essential tool for assessing the extent of FMH, particularly in cases where the volume is critical for determining the need for Rh immunoglobulin therapy or further medical intervention.

Understanding the significance of this detection threshold is essential as it informs clinical decisions, especially in Rh incompatibility situations where the identification of FMH can impact outcomes for both the mother and the fetus. When considering the other choices, they reflect larger volumes of FMH that the rosette test can also detect, but its design specifically allows for the accurate detection of even the smallest quantity mentioned.