Threatened miscarriage is a common complication of pregnancy. Despite initial viability confirmation by ultrasound scan, some of these patients had further spontaneous abortion. A highly sensitive and specific biomarker would be useful to determine the outcome of pregnancy and to prevent emotional impact to these women. A prospective 14-month cohort study was conducted in the Obstetrics and Gynaecology Department of Universiti Kebangsaan Malaysia Medical Centre to determine whether low serum levels of pregnancy-associated plasma protein A (PAPP-A) measured in early pregnancy can predict the outcome of threatened abortion. 42 pregnant women between 6 to 22 weeks of gestation with threatened abortion and 40 controls were enrolled. Serum samples were collected at presentation and PAPP-A was assayed by electrochemiluminescent immunoassay technique. Pregnancies were followed-up until 22 weeks of gestations and the outcome documented. Nine patients (11%) developed spontaneous abortion and 73 patients (89%) had successful pregnancy. The median PAPP-A level was significantly lower in patients with spontaneous abortion compared to those who had successful pregnancies in the threatened abortion group: 0.78 MoM (0.41-1.00 MoM) vs 1.00 MoM (1.00-2.0 MoM) respectively (p < 0.05). The best sensitivity of 44% and specificity of 93% were obtained at the cut of value of 0.66 MoM (95% CI, 0.561-0.773). In conclusion, low PAPP-A value in threatened abortion women is associated with pregnancy failure, although the use of PAPP-A as a one-time single marker has limited value.