BACKGROUND: Miscarriage is the most common complication of pregnancy. Various serum biomarkers in pregnancy which predict spontaneous miscarriage have been previously investigated but with conflicting results. A biomarker such as pregnancy associated plasma protein A (PAPPA) may likely prognosticate the clinical progress of pregnancy in early pregnancy assessment. OBJECTIVES: To determine the levels of maternal serum PAPP-A in women with threatened miscarriage and compare with those with normal ongoing pregnancy, and to evaluate its predictive role in spontaneous miscarriage among those with threatened miscarriage at the Lagos University Teaching Hospital (LUTH). METHOD: It was a prospective cohort study involving 98 pregnant women with threatened miscarriage and 98 pregnant women with normal ongoing pregnancy between gestational age of 6 and 20 weeks. After enrolment, blood samples were collected from the participants for the purpose of measuring the PAPP-A serum levels and they were followed up till 28weeks gestation (age of viability) for any adverse outcome especially miscarriage and then till delivery to determine other outcome of the pregnancy (such as gestational age at delivery, birth weight, preeclampsia/pregnancy induced hypertension). Statistical analysis was performed using the Stata version 16 (STATA Corp USA). Mann Whitney U test was used to compare the PAPP-A levels of those with miscarriage before 28weeks and the PAPP-A levels of those with ongoing pregnancy beyond 28weeks.Univariable and multivariable logistic regression was conducted to determine the predictive value of PAPP-A levels in determining progress of pregnancy beyond 28weeks.