Table S1.

Data collection and aligning methods for conception, abortion, and LARC usage methods

	Conception	Abortion			LARC usage method
	Conception rates	Age-standardized abortion rates	Crude abortion rates	Repeat abortion	DEPO	IMP/NEXP	MIR	NOR	IUD
Source/data collection method	Conception Statistics reports for England and Wales from 1998–2011, published by the Office for National Statistics	Department of Health	Department of Health	Department of Health	IMS British Pharmaceutical Index and IMS Hospital Pharmacy Audit for primary and secondary sales data				IMS Disease Analyzer for primary care sales; number of first contacts with women at Community Contraceptive Services as reported in KT-31
Transformation 1	For aligning secondary care IUD (KT-31) data prior to 2006–2007 with conception rates, it is assumed that data for ages 13–15 years is for age 15 years, and data for ages 16–19 years is split evenly into ages 16–17 years and ages 18–19 years	For aligning secondary care IUD (KT-31) data prior to 2006–2007 with age-standardized abortion rates for ages 15–44 years, it is assumed that data for ages 13–15 years is for age 15 years only, while all remaining age categories are combined	Crude abortion rates for ages 25–34 years are obtained by combining data for ages 25–29 years and ages 29–34 years	For repeat abortions, data for all ages <25 years are assumed to be for ages 15–24 years, and data for all ages are assumed to be for ages 15–44 years	Breakdown by age (15–17, 18–19, 2 0–24, 15–24, 25–34, 35–44, and 15–44 years) was performed by assuming the same distribution of patients as in the IMS Disease Analyzer ® data for primary care and in KT-31 for secondary care				Assumed that women who attend the clinic in a given year have their IUD fitted that year and not in previously, and that women who obtain a fitted IUD do not return to the clinic
Transformation 2	For aligning secondary care IUD (KT-31) data for 2006–2007 and after with conception rates for ages 15–17 years, data for age 15 years and ages 16–17 years are combined	For aligning secondary care IUD (KT-31) data for 2006–2007 and after with age standardized- abortion rates for ages 15–44 years, the data for ages <15 years are excluded and all remaining age categories are combined	For aligning secondary care IUD (KT-31) data prior to 2006–2007 with crude abortion rates: for ages 15–44 years, it is assumed that data for ages 13–15 years is for age 15 years only while all remaining age categories were combined; for ages 15–17 years, it is assumed data for ages 13–15 years is for age 15 years only, while data for ages 16–19 years is split into ages 16–17 years and ages 18–19 years; for ages 16–19 years, it is assumed data for ages 16–19 years is split into 16–17 years and 18–19 years	For aligning secondary care IUD (KT-31) prior to 2006–2007 with repeat abortion rates: for ages <25 years, it is assumed that data for ages 13–15 years are for age 15 years only, and data for ages <16 years, 16–19 years, and 20–24 years are combined; it is assumed that data for ages 13–15 years are for age 15 years only, while all remaining age categories are combined	UK data were applied a year-specific population ratio in order to derive England-specific sales data for secondary-care LARC sales between 1998–2006 from IMS Hospital Pharmacy Audit				Annual secondary care IUD data from KT-31 reports covered a period from April 1 to March 31; secondary-care IUD data were therefore redistributed into calendar years
Transformation 3			For aligning secondary care IUD (KT-31) data for 2006–2007 and after with repeat abortion rates: for ages 15–44 years, exclude data for ages <15 and combine remaining age categories; for ages 15–17 years, combine data for age 15 years and ages 16–17 years	For aligning secondary care IUD (KT-31) data for 2006–2007 and after with repeat abortion rates: for ages <25, data for ages 15, 16–17, 18–19, and 20–24 years are combined; for all ages, ages <15 is excluded and all remaining categories are combined	Incomplete DEPO primary-care sales data for 1998–2008 required these sales to be adjusted, and the average difference observed between the trends over the 1998–2008 period and over the entire period was added to the original sales values

Abbreviations: DEPO, Depo-Provera; IMP, Implanon; IUD, Intrauterine device; LARC, long-acting reversible contraceptives; MIR, Mirena; NEXP, Nexplanon; NOR, Noristerat.