RESUMO
Background: Unintended pregnancy is a major public health concern due to its impact on maternal morbidity and mortality. Contraceptive failure is one of the causes of unintended pregnancy. Data on factors associated with contraceptive method failure is scarce. This study therefore aimed to explore factors associated with contraceptive failure. Methodology: Unmatched case-control study was conducted at five Level One Hospitals in Lusaka. Convenience sampling was used to enrol 108 cases for whom pregnancy occurred while on a modern contraceptive method and 108 hospital-based controls who were on a modern contraceptive method and not pregnant. Binary and multiple logistic regressions were utilized for assessment of factors associated with failed contraception. Results: Among the 108 cases, 46 (42.6%), 40 (37%), 17 (15.7%) and 1 (0.9%) were on the oral contraceptive pill, injectable, implant and intrauterine device contraception methods respectively while 2 (1.9%) were on barrier and emergency contraceptive methods respectively. The odds of contraceptive failure when using the oral contraceptive pill was more than 7 times (AOR 7.790, 95% CI 1.210-50.161, p=0.031). Those who had contraception failure were more than 3 times more likely to be younger than 30 years old compared to those whose contraceptive method did not fail (AOR 3.559, 95% CI 1.100-11.521, p=0.034 and AOR 3.596, 95% CI 1.354-9.550, p=0.010 respectively for age groups 18-24 years and 24-30 years old). Other factors associated with higher odds of contraceptive failure were duration of marriage greater than one year, with the highest odds in those married for more than 10 years (AOR 9.744, 95% CI 2.232-42.537, p=0.002), higher social support (AOR 2.402, 95% CI 1.085-5.321, p=0.031), multiparity (AOR 15.299, 95% CI 3.034- 77.151, p=0.001), and duration of use of antecedent contraception method of more than 2-3 years (AOR 4.913, 95% CI 1.662-14.526, p=0.004). Conclusion: The oral contraceptive pill, younger age, marriage duration of more than one year and contraceptive use more than three years were associated with contraceptive failure. Good messaging and counseling on usage of the oral contraceptive pill are recommended.