INTRODUCTION: The present study aimed to assess the demographic, socioeconomic, medical and lifestyle factors associated with the progression of a threatened miscarriage to a complete miscarriage in the first trimester. METHODS: A prospective cohort study was conducted on 157 women who presented with vaginal bleeding in the fifth to tenth week of gestation. Cox regression analysis was used to determine the risk factors for progression to a complete miscarriage within 16 weeks of gestation. RESULTS: Of the 139 women included for data analysis, 36 (25.9%) had a miscarriage, mostly within two weeks of presentation. The results of our study showed that women aged ≥ 34 years were more likely to miscarry (hazard ratio [HR] = 1.95). Compared to women whose partner was 20-30 years of age, women whose partner was ≥ 41 years of age also had a higher likelihood of experiencing a miscarriage (HR = 8.33). However, the presence of nausea (HR = 0.33) and a high stress score (i.e. ≥ 17) on the Perceived Stress Scale (HR = 0.49) were associated with a reduced likelihood of miscarriage. CONCLUSION: Older pregnant women experiencing a threatened miscarriage should be counselled about their higher risk of miscarriage, especially if they have an older partner.