Abstract
The New Zealand abortion rate declined significantly from 2008 to 2014. Internationally, increased use of LARC methods has been recognised as having played an important role in declining abortion rates. LARC are highly effective methods of contraception (including intrauterine methods and implants) that have very low failure rates, high user continuation and satisfaction rates and can remain in place for up five or ten years. The subsidisation of the Jadelle subdermal contraceptive implant in 2010 served to remove the cost barrier for many New Zealand women.
This study was designed to investigate the hypothesis that an increased uptake of LARC methods was associated with the decreased abortion rate in New Zealand. The research had three main aims. First, to describe changes in the abortion rate with analysis by ethnicity, age, and ethnicity specific age-groups. Second, to describe changing patterns in contraceptive methods prescribed over time (including short and long-acting methods). The third aim was to investigate the association between the increased use of LARC and the declining abortion rate.
Contraceptive prescription data were collected from the Ministry of Health, and abortion and population data were collected from Statistics New Zealand. Statistical methods used to test the association between abortion and contraception were Poisson regression, and rates and rate ratios to measure the changing abortion rates and contraceptive rates.
The results showed that ‘Pacific’ and ‘Asian’ women experienced the greatest decline in abortion rates across all age-groups, whereas ‘European and other’, and ‘Māori’ women only experienced declining abortion rates in younger age-groups. The estimated prevalence of Jadelle increased from 2010, and the estimated prevalence of ‘all LARC’ (Jadelle, copper IUD and Mirena IUS) increased from 2009. Prescription rates for shorter acting methods including the oral contraceptive pill, depot medroxyprogesterone acetate (DMPA) and the emergency contraceptive pill generally decreased in the period 2004 to 2014.
The results of the Poisson regression showed that the increasing prevalence of the Jadelle implant was significantly associated with the declining abortion rate.However the poor fit of the model indicated that the increased prevalence of Jadelle did not fully explain the decline and that other factors are likely to have contributed to the decline. The increased use of the copper IUD and the Jadelle implant (combined) was found to be significantly associated with declining abortion and this model had the best fit of all models tested (by Akaike's Information Criterion). Therefore, the declining abortion rate was better explained by the combination of LARC methods.
This research is the first attempt to examine potential explanatory factors behind New Zealand’s declining abortion rate. While a number of other factors are likely to have contributed to the observed decline in abortion rates including societal, attitudinal, educational, and behavioural factors, they are far more challenging to assess. Due to the limitations in data available for analysis, questions remain about the extent to which changing patterns of contraceptive use contributed to the observed decline. Further research would be helpful to more clearly understand the relationship between LARC use, age, ethnic group and abortion. The marked decline in abortion rates for younger women might be explained by a shift towards use of more effective LARC methods (including the copper IUD) for this group. Research into the impact of behavioural, educational and attitudinal factors that may be related to unintended pregnancy risk would also help to clarify the role of non-contraceptive factors on the declining abortion rate.