Performance of single serum progesterone in the evaluation of symptomatic first-trimester pregnant patients: a systematic review and meta-analysis.

A single progesterone level provides a clinically useful prognostic information on pregnancy viability. More than nine out of ten patients with a level < 6.3 ng/mL (< 20.034 nmol/L) will be diagnosed with a non-viable pregnancy, and more than 90% of patients with a level ≥ 20-25 ng/mL (63.6-79.5 nmol/L) will have a viable pregnancy confirmed.