Introduction: Pain and bleeding complicate 30% of pregnancies threatening viability. The objective of this systematic review is to evaluate the role of a single progesterone level in predicting viability. Methods: We comprehensively searched MEDLINE, Embase (OVID), CINAHL and Cochrane databases from inception to July 2019. We included English language studies that enrolled symptomatic first trimester pregnant patients, measured progesterone and reported viability (miscarriage, ectopic or viable). We excluded studies with patients who had progesterone treatment, or conception after induced ovulation/invitro fertilization. We extracted patient characteristics, study setting, mean progesterone, the cut off value and outcome (viability). The quality of the included studies was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. We extracted data for 2X2 tables and report mean, standard deviation (SD), sensitivity, specificity, positive and negative predictive values (PPV, NPV). Results: Of the 689 studies screened, 51 studies with 15783 patients were included (1 randomized control trial, 36 prospective, 9 retrospective, 5 prospective case control studies) and 7553 were viable pregnancies. Of the 31 studies (n = 10998) that reported ectopic, 1661 patients were diagnosed with ectopic pregnancy. In 35 studies (n = 6003) that reported mean and SD, the levels were higher in viable (26.7 ± 11.2ng/ml) than non-viable (9.5 ± 5.9ng/ml; p < 0.001) or ectopic pregnancy 9.5 ± 6.8ng/ml (p < 0.001). The pooled diagnostic characteristics at different cut-off values were: <6.3ng/mL (9 studies; N = 6033) sensitivity 65.0% (95%CI 63.5,66.5), specificity 97.3% (95%CI 95.5, 98.5), PPV 99.4% (95%CI 99.1,99.7) and NPV 27.4 (95%CI 26.6,28.4); <10 ng/mL (12 studies with 5743 participants) sensitivity 65.0% (95% CI 63.5, 66.5), specificity of 97.3% (95%CI 95.5, 98.5), PPV 99.4% (95% CI 99.1, 99.7) and NPV 27.4% [95% CI 26.5, 29.4); 11-20 ng/mL (24 studies with 7141 participants) sensitivity 77.3% (95% CI 76.2,78.4), specificity 64.6% (95% CI 63.2, 65.9), PPV 73.2% [95% CI 72.3, 73.9) and NPV 69.5% (95% CI 70.7, 72.5). There was low risk of bias for patient selection, index test and low concern regarding applicability. The highest risk (82% of studies) was due to outcome ascertainment bias due to non-blinding of index and additional tests. Conclusion: A single progesterone value is useful in predicting viability of pregnancy among symptomatic patients.