Risk of unsafe abortion associated with long-term contraception behaviour: a case control study from Sri Lanka

BACKGROUND: When faced with an unintended pregnancy, some women choose to undergo an unsafe abortion, while others do not. This choice may depend on long-term contraception that shapes the fertility goals of women, along with many other risk factors. We assessed the risk for unsafe abortion associated with contraceptive practices based on women’s long-term behaviour, and its likely modification by the use of different types of contraceptives among women in Sri Lanka. METHODS: An unmatched case-control study was conducted in nine hospitals among 171 women admitted for care following an unsafe abortion (Cases) and 600 women admitted to same hospitals for delivery of an unintended term pregnancy (Controls). Interviewer-administered-questionnaires assessed their socio-economic, reproductive and fertility (decisions on family size, family completion) characteristics, contraceptive method last used (traditional, modern), reasons for discontinuation/never-use, and contraceptive practices assessed at different time points. Using several regression models, the risk of abortion was assessed for ‘non-use’ of contraception against ‘ineffective use’ at conception; for non-use further categorised as ‘never-use’, ‘early-discontinuation’ (discontinued before last birth interval) and ‘late-discontinuation’ (discontinued during last birth interval); and for any interaction between the contraceptive practice and contraceptive method last used among the ever-users of contraception. RESULTS: At conception, ‘non-use’ of contraception imparted a two-fold risk for abortion against ineffective use (adjusted-OR = 2.0; 95% CI: 1.2–3.2). The abortion risk on ‘non-use’ varied further according to ‘early’ (adjusted-OR = 1.7; 95% CI: 1.1–3.1) and ‘late’ (adjusted-OR = 2.3; 95% CI: 1.5–3.6) discontinuation of contraception, but not with ‘never-use’ (crude-OR = 1.1; 95% CI: 0.6–2.3). Among the ever-users, the risk of abortion varied within each contraceptive practice by their last used contraceptive method and reasons for discontinuation. A significant interaction between modern contraceptives and early discontinuation (adjusted-OR = 1.4; 95% CI = 1.1–3.1) demonstrated a seven-fold abortion risk for early discontinuation of modern methods against its ineffective use. In particular, hormonal methods seemed to be responsible for this risk (51.1% cases versus 42.5% controls). CONCLUSIONS: Long-term contraceptive practices showed varying risk for abortion, and was further modified by early discontinuation of modern contraceptives. This knowledge should be applied during postnatal visits by public-health staff. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12884-017-1376-7) contains supplementary material, which is available to authorized users.