Currently there is a blood test for a pregnancy-specific protein that can be conducted 30 days post-insemination. The milk progesterone level may be an indicator of pregnancy status; however, levels may also be elevated when a cow is mid-cycle. Consequently, it is best used to define a cow as not pregnant or open. Other tests have and will continue to be developed. It is critical for farmers to ask for documented peer-reviewed research and literature to assure validity, accuracy, and application of these tests and products. Both rectal palpation and ultrasound can be used to diagnose pregnancy. Typically both are performed by licensed veterinarians.

Dave Fischer, Extension Dairy Educator, University of Illinois - Illini DairyNET
and
Ellen Jordon, Extension Dairy Specialist, Texas A & M