Women's Use of Long-Acting Reversible Contraception for Birth Timing and Birth Stopping

Abstract

The use of long-acting reversible contraceptive (LARC) methods—intrauterine devices (IUDs) and implants—has recently expanded rapidly in the United States, and these methods together approach the contraceptive pill in current prevalence. Research on LARCs has analyzed their use to reduce unintended pregnancies but not their use to enable intended pregnancies. Knowledge of both is necessary to understand LARCs’ potential impacts on the reproductive life courses of U.S. women. We combine data from two nationally representative surveys to estimate women's likelihood and timing of subsequent reproductive events, including births resulting from an intended pregnancy up to nine years after discontinuing LARC use. We estimate that 62% of women will give birth, and 45% will give birth from an intended pregnancy. Additionally, 18% will have a new LARC inserted, and 13% will transition to sterilization. Most of these reproductive events occur within two years after discontinuing LARC use. Births from an intended pregnancy are especially common when no intervening switch to another contraceptive method occurs. We infer that women's motives for using LARC are varied but include the desire to postpone a birth, to postpone a decision about whether to have a(nother) birth, and to transition definitively to the completion of childbearing.

Introduction

The twenty-first century has seen rapid growth in the use of long-acting reversible contraceptive (LARC) methods—intrauterine devices (IUDs) and implants—in the United States. LARC use among U.S. women has increased from close to 1% of contraceptive use in 1995 to 6% in 2008 and to 16% in 2017–2019 (Daniels and Abma 2020; Hubacher et al. 2011; Kavanaugh and Jerman 2018; Kavanaugh et al. 2011). In 2014, IUDs (12%) were the fourth most used contraceptive method after the Pill (25%), female sterilization (22%), and the male condom (15%). Implant use accounted for 3% of contraceptive use, up sharply from 0.5% in 2008 (Kavanaugh and Jerman 2018). IUDs and implants have much lower contraceptive failure rates than all other reversible methods (Sundaram et al. 2017; Winner et al. 2012). In addition, these methods have been shown to have higher continuation rates (Peipert et al. 2011; Simmons et al. 2019) and higher user satisfaction (Peipert et al. 2011; Sittig et al. 2020). Foster et al.'s (2015) survey of more than 100 contraceptive researchers found median and modal projections of U.S. women's combined IUD and implant use in the absence of common access barriers in the range of 25% to 29% of contraceptive use.

Quantitative research into LARCs' impacts until now has largely been from a public health perspective that has emphasized LARCs' potential for reducing women's risk of unintended pregnancy (e.g., Parks and Peipert 2016). The use of highly effective and reversible contraception, however, should better enable women to achieve a broader set of reproductive goals than that of reducing the risk of unintended pregnancy (Dehlendorf et al. 2018). We argue that a major criterion against which a new contraceptive method should be evaluated is whether it increases women's ability to have births of their desired number and timing over the reproductive life course—that is, to have intended births. Hence, the present study's principal focus is on women's success in achieving intended pregnancies resulting in births following LARC use and subsequent discontinuation of use. Additionally, we are interested in women's use of LARC as an intermediate method that may be a precursor to her transitioning to an equally effective but permanent method (i.e., female or male sterilization). Our investigation of reproductive events following LARC use thus allows for a shift of focus from contraception as pregnancy prevention to contraception as a means toward achieving a woman or couple's family planning goals.

We first use a multinomial regression model to study the associations of a woman's sociodemographic characteristics with experiencing any of three reproductive events in a given year of exposure up to nine years following discontinuation of LARC use: (1) giving birth, (2) new LARC insertion, and (3) initiating contraceptive sterilization. Second, we use a synthetic cohort life table methodology—similar to that used to describe, for example, the length of time until divorce (Martin 2006) or until remarriage (McNamee and Raley 2011)—to trace the cumulative reproductive life course implications of a woman's annual rates of experiencing each of the three reproductive events. We estimate not only the proportion of LARC discontinuations that end in a birth but also the proportion of discontinuations that end in a birth from an intended pregnancy. Our simulated reproductive life course measures thereby include (1) a cumulative fertility rate, consisting of the proportion of women who discontinue LARC use and who then subsequently have another birth; and (2) a cumulative intended fertility rate, consisting of the proportion of women who discontinue LARC use and have a next birth that results from an intended pregnancy. We also simulate a cumulative rate of new LARC insertion and a cumulative rate of initiating contraceptive sterilization, each as a proportion of all women who discontinue LARC use. Our simulation estimates these outcomes after up to nine years of exposure to reproductive events among women up to 34 years old at the time of LARC discontinuation.

Our data are from women who have used and then stopped using a LARC device. Only recently, however, have LARC devices been used to any substantial extent in the United States among the current generation of women of reproductive age. Therefore, relatively few women have had any years of exposure after LARC use to observe, and even fewer have had even moderately long periods of fertility exposure following LARC use. We address this data challenge by pooling observations from two nationally representative data sources: the 2006–2017 years of the National Survey of Family Growth (NSFG) and the 2002–2017 waves of the National Longitudinal Survey of Youth 1997 (NLSY97). We assess the appropriateness of pooling observations across the two surveys using formal statistical methods.

We estimate that within nine years of discontinuing LARC, 62% of women will have a birth, and 45% of women will have a birth resulting from an intended pregnancy. Additionally, within nine years of discontinuing LARC, 31% of women will either have a new LARC inserted or begin sterilization as their method of contraception. Hence, we infer substantial successful use of LARC to realize women's plans for their birth timing and to facilitate women's or couples' decision-making about whether and when to definitively end their exposure to childbearing.

Literature Review

Until very recently (Hubacher and Kavanaugh 2018), the United States has had one of the lowest rates of LARC use among low-fertility countries (Buhling et al. 2014; Eeckhaut et al. 2014). LARCs in the United States—first-generation IUDs, such as the Lippes Loop—date back to around 1960 (Thiery 1997). However, their take-up was shortly followed by steep declines in usage when serious safety concerns regarding the Dalkon Shield IUD in the early 1970s resulted in a prolonged period of litigation (Sonfield 2007). IUD use was revived in the United States after the levonorgestrel-releasing IUD was approved for medical use in 2000 (Kavanaugh et al. 2011). Although IUDs remain the dominant LARC in the United States, as they do in most other developed countries (Eeckhaut et al. 2014; United Nations 2013), implant use has also increased rapidly in recent years, doubling from 1.3% of current contraceptive users in 2012 to 2.6% in 2014 (Kavanaugh and Jerman 2018). The first implant—Norplant—was approved in 1990, but there were early gaps in the availability of the method, and Norplant was withdrawn from the market in 2002. The second implant method, Implanon, was not approved until 2006; it was replaced by its newer version, Nexplanon, in 2011 (Strasser et al. 2016).

Health insurance has been slow to cover the high up-front cost of LARCs. Until the introduction of the Affordable Care Act in 2010, LARC devices and their insertion cost were omitted from many health insurance plans (Bearak et al. 2016; Sonfield 2007). Reforms to Medicaid policy have provided coverage for immediate postpartum LARC insertion across an increasing number of states (Moniz et al. 2015; Rodriguez et al. 2014). In addition, several localities and states have seen efforts to increase LARC use more broadly, including the Contraceptive CHOICE Project in St. Louis, Missouri; the Colorado Family Planning Initiative (CFPI) in Colorado; the HER Salt Lake Contraceptive Initiative in Utah; and the Delaware Contraceptive Access Now (DEL-CAN) initiative in Delaware. At the same time, however, a growing body of reproductive justice–based work has issued warnings about the potentially negative impact on women's reproductive autonomy resulting from efforts aimed at increasing LARC use rather than increasing access to the full range of contraceptive methods (Dehlendorf et al. 2018; Gomez et al. 2014; Higgins 2014).

Arguments for, and research on, LARC access and use in the United States have centered on LARCs' potential to reduce unintended pregnancy (Karpilow and Thomas 2017; Lindo and Packham 2017; Parks and Peipert 2016; Peipert et al. 2012; Ricketts et al. 2014; Secura et al. 2014; Trussell et al. 2013; Wu and Mark 2018). Reducing the high level of unintended pregnancy among U.S. women has been a public health priority for decades (Cutright and Jaffe 1976). Despite its shortcomings in terms of describing or predicting the behavior of any particular individual (Higgins et al. 2012; Potter et al. 2019) and failure to capture affective dimensions (Geist et al. 2019; Higgins 2017), pregnancy intendedness has been shown to be a valuable concept at the population level (Kost and Zolna 2019; Santelli et al. 2003). Pregnancy intentions have been found to show extraordinary consistency at the aggregate level, and they constitute a valuable predictor of population-level fertility as well as a key indicator of the need for contraceptive and abortion services. Thus, pregnancy intentions are important in assessing progress toward improving women's reproductive health and well-being.

The United States has a substantially higher rate of unintended pregnancy than other high-income countries. In a cross-national comparison of unintended pregnancy around 2012, Sedgh et al. (2014) showed that North America (the United States and Canada) had an unintended pregnancy fraction—at 51%—that was as much as 50% higher than in other high-income countries. For example, comparative rates were 38%, 34%, and 37% of pregnancies, respectively, in Northern Europe, Western Europe, and East Asia and Oceania. Unintended pregnancies are associated with adverse birth and maternal health outcomes (Kost and Lindberg 2015; Lindberg et al. 2015). Therefore, increasing access to and use of LARC in the United States to reduce unintended pregnancies has been promoted as a public health goal (American College of Obstetricians and Gynecologists [ACOG] 2009, 2015; Wu et al. 2018). The use of LARC, however, should enable women to achieve their reproductive life course goals beyond those linked to reducing the risk of unintended pregnancy (Dehlendorf et al. 2018). Crucial among its potential purposes is the extent to which LARC use increases women's ability to have births of their desired number and timing over the reproductive life course—that is, to have intended births. A related reason for attending to the impact of LARC use on intended fertility that should be of major salience to demographers is that unless reductions in unintended fertility achieved through LARC use are counterbalanced by positive impacts on intended fertility, overall U.S. fertility will decrease markedly with increased LARC use. The U.S. total fertility rate (TFR), at 1.73 in 2018 (Martin et al. 2019), stands well below replacement level (although see also Wu and Mark 2019). With unintended fertility accounting for approximately 35% of all U.S. births (Hayford and Guzzo 2016), a simple subtraction of all unintended births would leave the TFR at 1.12, squarely within the range of lowest-low fertility (Kohler et al. 2002).

We argue that efforts to shape the use of LARC methods in the United States need to be grounded in a fuller understanding of their impact on women's reproductive life courses. We note here that LARC devices are marketed as being a fully effective contraceptive method for 3 (implant and Skyla hormonal IUDs), 5 (Mirena, Liletta, and Kyleena hormonal IUDs), or 10 years (Paragard copper IUD) (ACOG 2015; U.S. FDA 2018). Following a reproductive life course perspective, use of LARC may increase intended fertility in two ways: (1) a birth that would have occurred earlier than desired (and thus resulted from an unintended pregnancy) may instead occur later, as a birth resulting from an intended pregnancy; and (2) a birth that would not have occurred at all because the woman opts to rely on sterilization (which she would have come to regret) may instead occur and result from an intended pregnancy. That is, some women who would have eliminated their risk of unintended pregnancy by using a permanent method (contraceptive sterilization) might, following a period of LARC use in place of sterilization, experience a change in fertility goals and go on to have (further) intended pregnancies. As many as one in four women in the United States who are sterilized subsequently report that they would like to have their sterilization reversed (Eeckhaut et al. 2018).

On the other hand, LARC use could also work to reduce intended fertility if LARCs' comparatively low risk of contraceptive failure works to prevent both intended and unintended pregnancies. First, research has shown that only 68% of pregnancies resulting from contraceptive failure are reported as unintended (Trussell et al. 1999), and therefore reducing contraceptive failure will potentially prevent some number of pregnancies that would subsequently be reported as intended. Second, barriers to LARC removal experienced by women who may either have been ambivalent or have changed their intentions about wanting to become pregnant (Amico et al. 2020; Strasser et al. 2017) could have the effect of delaying or even preventing pregnancies that would be reported as intended.

We know of no previous study that has investigated the fraction of women that go on to have any birth or an intended birth following LARC discontinuation. Kramer et al. (2018), however, found that among current LARC users, 57% of Black women, 45% of Hispanic women, and 38% of non-Hispanic White women report either desiring future children or being unsure about their intentions. This finding suggests considerable potential for intended fertility following LARC discontinuation. We know of no direct evidence on the role of LARC use in increasing births resulting from an intended pregnancy through substituting LARC for contraceptive sterilization. Suggestive evidence, however, is found in the substantial increases in LARC use between the late-2000s and mid-2010s that coincided with substantial decreases in sterilization (Kavanaugh and Jerman 2018). Moreover, in a nine-country study of couples' contraceptive use in the mid- to late-2000s, Eeckhaut et al. (2014) found that those countries with the lowest prevalence of LARC use (Australia and the United States) had by far the highest prevalence of contraceptive sterilization. Greater use of LARC in place of sterilization might therefore be associated with more intended pregnancies before a permanent end to a woman's exposure to pregnancy, and that permanent end to exposure may occur either through the woman's aging out of her reproductive years or through the woman's initiation of contraceptive sterilization at a later age during her reproductive years.

Methods

Data for this study are drawn from the NSFG's 2006–2010, 2011–2013, 2013–2015, and 2015–2017 cycles (U.S. Department of Health and Human Services 2018) and the NLSY97's annual 2002–2011 waves and biennial 2013, 2015, and 2017 waves (Bureau of Labor Statistics n.d.). Additional details on the two sources are given in the online appendix, section A.

For both surveys, we analyze samples of women who reported having used and then discontinued the use of a LARC. A major difference between the NSFG and the NLSY97 is in their sampling. The NSFG sampled over multiple cross sections of U.S. reproductive-age women from 2006 through 2017. The NLSY97 sampled from the population of young women who were born between January 1, 1980, and December 31, 1984, and resided in the United States in 1997; it then followed these women as they aged through to their early to mid-30s in 2017. We discuss differences in the sociodemographic composition of LARC-discontinuing women between the two surveys as a result of these different sampling and observation schemes when presenting descriptive results from Table 1, and we discuss potential implications of these survey differences for the estimation of reproductive event risks when presenting the results of the multivariate estimation of those event risks in Table 2.

A second major difference between the NSFG and the NLSY97 is that the NSFG identified contraceptive method from a monthly contraceptive calendar involving just over three years of recall, whereas the NLSY97 identified contraceptive method from an annual contraceptive-use report involving recall only in the last 12 months. The implications of these offsetting advantages and disadvantages in terms of the reporting period (months vs. a year) and the length of the recall period (three or more years vs. only one year) for estimation bias are unclear. We present comparisons of event hazard risks by single year of duration since LARC discontinuation between the NSFG and NLSY97 (see the online appendix, section B) and find that overall patterns of annual demographic event risks between the two surveys are more similar than different.

Our main outcome of interest is whether the woman experienced a live birth. We define the cumulative fertility rate for up to nine post-LARC years of fertility exposure, where either one of two competing events may also end her spell of fertility exposure: a new LARC insertion or sterilization. Cumulative risks of a new LARC insertion and of sterilization are similarly defined for up to nine years following LARC discontinuation. We also consider whether the woman experienced a live birth that resulted from an intended pregnancy. We define the intended fertility rate as the proportion of all women who discontinue LARC use and subsequently have a next birth that results from an intended pregnancy. We specify the intended fertility rate as the product of the cumulative fertility rate and the conditional probability that any birth that does occur is the result of an intended pregnancy.

The cumulative fertility rate, the cumulative new LARC insertion risk, and the cumulative sterilization risk are calculated from an annual competing hazard of birth, new LARC insertion, and sterilization by the number of years since LARC discontinuation (upcoming Eq. (1)). We use both NSFG and NLSY97 data to estimate this hazard. Combining data from the two surveys requires that we simplify the sequences of contraceptive method use and discontinuation to those occurring in annual periods. We code events in the NSFG by the calendar year in which they occurred; we code events in the NLSY97 by the approximately 12-month period between annual survey waves, imputing those events in the years between the biennial survey waves 2011–2017 (that is, in 2012, 2014, and 2016; see the online appendix, section A, for more details). For the NSFG, year 0 indicates the calendar year that includes the month of last reported LARC use before the month of first reported non-use of LARC. For the NLSY97, year 0 indicates the approximately 12-month period between the waves of last reported LARC use (retrospectively reported LARC use over the 12 months before the more recent wave). For the NSFG, most women can be followed in the year of LARC discontinuation (year 0) and for only one (year 1) or two (year 2) years after the year of LARC discontinuation because of the limited period covered by the NSFG contraceptive calendar (i.e., a maximum of three to four years). For the NLSY97, women can be followed for up to 11 years after the year of LARC discontinuation (year 0). However, because of the very sparse data at long durations, we limit our simulated period to nine years, from year 0 to year 8.

Our estimation of the intended fertility rate combines data on the cumulative fertility rate (a simplified version of upcoming Eq. (1)) with an estimate of the conditional probability that any birth that does occur is the result of an intended pregnancy. Direct information on the intendedness status of a pregnancy resulting in live birth after LARC discontinuation comes from NSFG data only. Intendedness was measured with a series of retrospective NSFG questions asking the woman to report her pregnancy intentions (e.g., “Right before you became pregnant. . . .”). Following previous work (Mosher et al. 2012), we code an intended pregnancy as one reported as having occurred at the right time or later than desired. Responses of “didn't care, indifferent” (N = 1) or “don't know, not sure” (N = 1) are also classified as intended. Information used in the prediction of intendedness status—specifically, duration since LARC discontinuation and whether the woman switched to a non-LARC method following LARC discontinuation—comes from both the NSFG and NLSY97.

Statistical Analysis

We code woman's characteristics—including her age, education, union status, parity, and race/ethnicity—at the time of LARC discontinuation. In addition, we include a predictor of the number of calendar years (NSFG) or survey years (NLSY97) during which the LARC device was used before it was discontinued. Finally, the number of years (“duration”) since LARC discontinuation is included because it is a key predictor variable in our study. In the NLSY97, we can code this from 12-month retrospective contraceptive use questions at each panel wave. In the NSFG, only 0, 1, and 2 years duration since LARC discontinuation can be coded from the contraceptive calendar. Therefore, for our analyses of reproductive events following LARC discontinuation, we use only these recently observed discontinuations in the NSFG.

To estimate the annual competing hazard with the full set of regressors (Eq. (1)), we pool observations of LARC discontinuers in the NSFG and NLSY97. We exclude the year of LARC discontinuation here—year 0—because of the very low hazard of any event occurring in year 0 (see Table A1 in the online appendix for the hazard calculated while including year 0). Ours is not the first study to conduct pooled estimation using NLSY cohort data and one other survey. Hellerstein and Imbens (1999) combined NLSY79 data with Current Population Survey data for labor market outcomes. Weden et al. (2012) combined NLSY79 data with Early Childhood Longitudinal Study, Birth Cohort data for a child obesity outcome. The Weden et al. (2012) study is closer to ours in its using the same regressor variables in both surveys. They evaluated the appropriateness of pooling observations across surveys using model fit assessment methodology described by Rendall et al. (2013), and we apply that same methodology in the present study (see the presentation and discussion of Table A3 in the online appendix).

All our estimates are weighted using the NLSY97 and NSFG sample weights. Before pooling observations across the four NSFG cycles (2006–2010, 2011–2013, 2013–2015, and 2015–2017), we normalize the weight of each cycle to have a mean of 1, and we normalize the weight of the NLSY97 similarly to have a mean of 1. This weighting ensures that equal weight is given to observations sampled in these different periods and in different surveys, as Rendall et al. (2008) recommended for pooled survey analysis. We additionally adjust for clustering and stratification in the NSFG-only analyses of Eq. (1). Because the clustering and stratification of observations occur differently between the NSFG and NLSY97, solutions for which have yet to be developed in pooled survey analysis, we do not adjust for these in our pooled-survey estimation.

In addition to the full competing-hazard model, we conduct a synthetic cohort simulation that joins the predicted probabilities from a simplified version of Eq. (1) with the conditional probability that any birth that does occur is the result of an intended pregnancy (see section B of the online appendix for details on the estimation of this conditional probability). We simulate nine years of post-LARC exposure to a birth (i.e., the fertility rate), to a birth resulting from an intended pregnancy (i.e., the intended fertility rate), to a LARC reinsertion, or to sterilization. This simulation includes as predictors only time since LARC discontinuation and whether a non-LARC method was used in the year before a birth. We use the latter as a proxy for whether a woman switched to a non-LARC method between LARC discontinuation and having a birth, given that this measure is available in both the NLSY97 and the NSFG. A full description of this simulation method is given in the online appendix, section B.

Results

Characteristics of Women Who Discontinue LARC

In Table 1, we describe U.S. women who discontinued LARC use between 2002 and 2017, as identified in the NLSY97 and NSFG. Previous studies have described current LARC users (e.g., Kramer et al. 2018; Xu et al. 2011) and the characteristics associated with early LARC discontinuation (e.g., Grunloh et al. 2013; Phillips et al. 2017). However, to our knowledge, no nationally representative study has described women who have discontinued LARC use. Although both the NSFG and NLSY97 provide such nationally representative estimates of women who discontinue LARC use in the observed 2002–2017 period, we prioritize description from the NSFG in our presentation of findings on the characteristics of LARC-discontinuing women for two reasons: (1) it covers women at all reproductive ages (15–44); and (2) its sampling over multiple cross sections of U.S. reproductive-age women from 2006 through 2017 allows for ongoing period representation of the sociodemographic characteristics of women discontinuing LARC use, including representation of recent immigrants. In contrast, the NLSY97 is sampled from the population of young women residing in the United States in 1997, thus representing a smaller fraction of Hispanic women than in the NSFG; the 1997 NLSY youth cohort is then followed as they aged through to their early to mid-30s. In our comparisons of estimates of characteristics of LARC-discontinuing women between the NSFG and NLSY97, we use the NSFG subpopulation of LARC discontinuers at ages 20 to 34. Our primary substantive interest in this study is of women who discontinued LARC use up to age 34 because for up to nine years following LARC discontinuation of our simulation, those women are still of reproductive ages and are therefore exposed to reproductive events.

The NSFG estimates are derived from a sample size of 718 women aged 15–44 and 550 women aged 20–34 (at the time of LARC discontinuation). The modal group of LARC discontinuers is aged 25–29 for both age ranges. The timing of the reintroduction of hormonal IUDs and implants into the U.S. market also means that the majority of LARC discontinuations have been recent. More than one-half of discontinuations occurred in 2012–2017, more than one-third occurred in 2007–2011, and fewer than 1 in 10 occurred in 2002–2006.

Hispanic women account for relatively large shares of LARC discontinuers (almost 30%), consistent with estimates of current LARC use among U.S.-born and especially foreign-born Hispanics (Tapales et al. 2018). Non-Hispanic White women account for one-half of women discontinuing LARC, followed by Black and Other race/ethnicity, at around 10% each. Women at all education levels are represented among LARC discontinuers, with high school graduates and those with some college being the largest two educational attainment groups. A relatively high fraction of LARC discontinuers were partnered at discontinuation: one-half of all discontinuers were married, and another one-fifth were cohabiting. The large majority of women were parous at the time of LARC discontinuation: just more than one-half had already given birth to at least two children, and approximately 30% had given birth to only one child. The modal duration of women's LARC use before discontinuation is four or more years (possibly coincident with the end of the device's life cycle), followed by durations of only one or two years of use. This result is broadly consistent with previous NSFG-based estimates of mean completed durations of IUD use of 47 months in the 2006–2010 NSFG data and 31 months in the 2011–2013 NSFG data (Gomez et al. 2016). Short durations may reflect method dissatisfaction or unintended expulsion of IUDs (Goldthwaite et al. 2017; Grunloh et al. 2013) or planning for a timely next birth.

Ages 20–34 correspond to the approximate overlap in ages at LARC discontinuation between the NLSY97 and the NSFG, providing us with LARC discontinuation distributions and subsequent dynamics from as many as 1,064 women in this age range. We present statistics separately for the NSFG and NLSY97 samples because the structure of cohort observation in the NLSY97 introduces some differences based on the different time of sample selection and different matches between age and period. In particular, most women in the NLSY97 cohort were in their mid-20s when LARCs were again increasing in popularity after the earlier IUD problems and the gap in implant availability following Norplant discontinuation. Thus, 30- to 34-year-olds account for a larger fraction of LARC discontinuers in the NLSY97 (36.2%) than do 30- to 34-year-olds represented in the 20- to 34-year-old NSFG sample (24.7%). College graduates are similarly more highly represented among NLSY97 LARC discontinuers (30.0%) than among 20- to 34-year-olds from NSFG-sampled LARC discontinuers (19.9%). The NLSY97 sample was selected from those residing in the United States in 1997, and this is apparent in the racial/ethnic composition, which has fewer Hispanic women (and more non-Hispanic White women) than in the NSFG estimates of LARC discontinuers. Distributions of women by calendar year, union status, and parity at LARC discontinuation, however, are similar between the estimates based on the 20- to 34-year-old NSFG sample and the NLSY97 sample of LARC discontinuers.

Sociodemographic and LARC History Predictors of Live Births, New LARC Insertions, and Sterilizations After LARC Discontinuation

Multivariate estimates of the relative risks ratios (RRRs) for a live birth, new LARC insertion, and sterilization after LARC discontinuation are shown in Table 2. These estimates are based on the pooled NSFG (all women ages 15–44) and NLSY97 samples. Model fit statistics supporting the pooling of observations across the two surveys are shown in Table A3 (online appendix).

Compared with the reference age group 30–34, women discontinuing LARC in their 20s have a higher risk of giving birth (RRR = 1.97 and 1.70, respectively, for those ages 20–24 and 25–29 at LARC discontinuation). Compared with non-Hispanic White LARC discontinuers, Black LARC discontinuers have a lower risk of birth (RRR = 0.69, p < .10), and Other race/ethnicity discontinuers have a higher risk of birth (RRR = 4.79). Being at parity 1 at LARC discontinuation is associated with a higher likelihood of birth than being nulliparous (RRR = 0.43) or being at parity 2 or above (RRR = 0.62). Being married at the time of discontinuing LARC use is also associated with a higher birth risk compared with cohabiting (RRR = 0.67) or being single (RRR =0.47). Very short duration (one year) of LARC use before discontinuing is associated with an elevated risk of birth (RRR = 2.43), as is a longer duration (four or more years) of LARC use before discontinuing (RRR = 1.53). Two years since discontinuation is the peak duration for birth risk. Having been one year since the year of LARC discontinuation (RRR = 0.61) or four or more years since the year of LARC discontinuation (RRR = 0.25) is associated with substantially lower birth risk.

The other two spell-ending reproductive events are new LARC insertion and sterilization. New LARC insertion is mostly dependent on the length of use of the previous LARC device. Women are much more likely to have a new LARC inserted if they had used the previous LARC device for only one year (RRR = 7.96). Women of Other race/ethnicity (RRR = 8.44) are much more likely to have a new LARC inserted than are non-Hispanic White women, and age 15–19 at discontinuation is associated with a lower risk of having a new LARC inserted (RRR = 0.18).

Regarding factors associated with sterilization, age has the expected positive gradient: sterilization risk is higher at ages above 35 (RRR = 3.51) upon LARC discontinuation and lower at ages 25–29 upon LARC discontinuation (RRR = 0.52, p < .10), compared with ages 30–34 upon LARC discontinuation. Higher parity is also positively associated with sterilization: those with two or more live births are more likely (RRR = 2.40) to transition to sterilization following LARC discontinuation than are those at parity 1. These findings are consistent with general reproductive life course expectations of who is most at risk of sterilization (Chandra 1998; Eeckhaut and Sweeney 2016). Finally, women are at higher risk of sterilization one year after the year of discontinuing LARC (RRR = 2.98), compared with the reference duration of two years since the year of LARC discontinuation. In these cases, we infer that the woman might have used LARC to defer a decision to stop childbearing and that she will replace her LARC device with a permanent method when she is more certain about the decision.

Before describing the results from our simulations of reproductive events subsequent to LARC discontinuation, for which we control only for years since discontinuation, we note how the similarities and differences in sociodemographic characteristics of LARC-discontinuing women between the NSFG (ages 20–34) and NSLY97 samples might impact our pooled-survey estimates of risks of those events. First, distributions for two of the strongest predictors of risks of reproductive events—union status and parity at LARC discontinuation—are substantively and statistically indistinguishable between the NSFG and NSLY97 (see Table 1). Being married and of parity 1 are the characteristics associated with the highest risk of birth following LARC discontinuation, and they account for, respectively, 47% and 33% of LARC discontinuers in both the NSFG sample ages 20–34 and the NLSY97 sample. Being of parity 2 or more is associated with easily the highest risk of sterilization following LARC discontinuation, and women of this parity 2 accounted for, respectively, 52% and 50% of LARC discontinuers in the NSFG sample ages 20–34 and the NLSY97 sample. Also reassuring is that one of the sociodemographic characteristics that differs most between the NSFG and NLSY97—that of Hispanic versus non-Hispanic White ethnicity (Hispanics represent 11 percentage points more LARC discontinuers in the NSFG than the NLSY97, see again Table 1)—does not have a substantively or statistically significant multivariate association with birth, new LARC insertion, or sterilization event risk. However, two other characteristics that have different distributions between LARC discontinuers in the NSFG ages 20–34 and the NLSY97 samples—age at discontinuation and the duration of LARC use before discontinuation—do have substantively and statistically significant multivariate associations with birth and sterilization events. Being aged 20–24 at LARC discontinuation is associated with almost twice the risk of giving birth relative to being aged 30–34 at LARC discontinuation, and 20- to 24-year-olds account for only 15% of LARC discontinuers represented by the NLSY97 sample versus 34% of LARC discontinuers represented by the NSFG age 20–34 sample. This difference may downwardly bias the annual birth hazards at three or more years following LARC discontinuation that are used in the simulation: only NLSY97 sample members can be used for those durations of three or more years. Countering this downward bias, however, is the lower fraction of NLSY97 sample members than NSFG aged 20–34 sample members who had been using a LARC device for four or more years before discontinuation (28% vs. 40%). This characteristic is associated with a much lower annual birth hazard than being of the reference category of two years of LARC use (represented by 36% of NLSY97 women vs. 21% of NSFG women aged 20–34). This higher fraction at two years than four or more years of LARC use before discontinuation in the NLSY97 will have an upward bias on annual birth hazards at three or more years following LARC discontinuation. Overall, then, the differences in sociodemographic characteristics between the NLSY97 and NSFG samples result in no clear direction of estimation bias implied for the simulation results, to which we now turn.

Simulation of Reproductive Events After LARC Discontinuation

Our simulation of births, new LARC insertions, and female or male sterilizations up to nine years after LARC discontinuation is summarized in Table 3. Only 7.4% of LARC discontinuations are estimated to result in none of these three reproductive events within nine years. By contrast, 61.9% of women are projected to have experienced a birth; 17.6%, a new LARC insertion; and 13.1%, female or male sterilization. The 61.9% of women experiencing a birth within the nine years following LARC discontinuation constitutes the cumulative fertility rate. These women include 45.2% of all LARC-discontinuing women who are projected to experience a birth resulting from an intended pregnancy. This constitutes the cumulative intended fertility rate.

We divide the occurrence of each of the reproductive events into three cumulative periods—0–2 years, 0–5 years, and 0–8 years—and we divide births into those occurring after switching to a non-LARC contraceptive method between the LARC discontinuation and the birth versus those births not preceded by contraceptive switching. Recall that the duration since LARC discontinuation and whether the woman switches to a non-LARC contraceptive method between the LARC discontinuation and the birth are the two factors in our simulation model that predict whether the woman reports that the birth is the result of an intended pregnancy. As shown in the last two rows of Table 3, among women who give birth without switching to a non-LARC method, 79.4% of births follow an intended pregnancy (36.6% of the 46.1% of women who give birth without switching), compared with 54.5% among women who give birth after switching to a non-LARC method (8.6% of the 15.8% of all LARC-discontinuers who switch methods and then give birth).

Regarding duration since LARC discontinuation, by two years after the year of discontinuation (year 2), 71.9% of all births that will eventually occur within nine years post-discontinuation will have already occurred (44.5% of a total of 61.9% women having a post-LARC birth). An even higher fraction (76.5%) of all births resulting from an intended pregnancy will have already occurred (34.6% of a total of 45.2% women having a post-LARC intended birth within nine years). By five years after the year of LARC discontinuation, almost all the LARC-discontinuing women who will experience a birth (58.0%) will have already done so. Moreover, only 14.8% of women discontinuing LARC will not have experienced any of a birth, new LARC insertion, or sterilization within five years. This follows from an especially high fraction of eventual sterilization events occurring by years 0–2 (8.8% of the cumulative sterilization rate of 13.1%) and a majority of eventual new LARC insertions occurring within years 0–2 (9.6% of the cumulative new LARC insertion rate of 17.6%). In years 6–8, another 3.9% of women will give birth, 1.9% will experience new LARC insertions, and 1.5% will experience transitions to sterilization.

Discussion

This study aimed to broaden the investigation of LARC beyond the focus of existing quantitative research on LARCs' potential to reduce unintended pregnancy to consider its potential to increase intended pregnancies resulting in births. We estimated that 62% of women who discontinue LARC use between ages 20 and 34 have a live birth within nine years of discontinuation. This is a relatively high proportion given that about one-half of LARC-discontinuing women in this age group already had two or more children. However, LARC discontinuers also had characteristics facilitative of going on to a next birth, including the more than two-thirds of women who were married or cohabiting at the time of LARC discontinuation. We estimated a cumulative intended fertility rate of 45%. That is, just under one-half of LARC discontinuers go on to have a birth that results from an intended pregnancy inside a spell of nine years after discontinuing LARC use. This is broadly consistent with Kramer et al.'s (2018) findings from an analysis of the birth intentions of current LARC users in 2011–2015, in which 45% of non-Hispanic White, 38% of Hispanic, and 57% of Black women expressed an intention to consider a future birth. We infer from this high intended fertility rate that many women were using LARC with the intention to successfully transition to an intended pregnancy following LARC discontinuation.

We also considered two other reproductive behaviors following LARC use and subsequent discontinuation of use. Most women who do not have a birth within nine years after discontinuing LARC have a new LARC inserted (18%) or initiate (female or male) contraceptive sterilization (13%). We estimated that only 7% of women experience none of these three reproductive events within nine years of LARC discontinuation.

Reproductive life course characteristics are not generally associated with the event of a new LARC insertion. Only having recently (within a year) had their LARC removed (or expelled) is strongly (and positively) associated with having a new LARC insertion, suggesting that LARC discontinuation may not have been due to readiness for pregnancy but instead due to problems with the previously inserted LARC device, such as IUD expulsion or dissatisfaction because of adverse side effects. By subsequently having a new LARC inserted—possibly of a different type—these women opted to continue highly effective but reversible pregnancy protection. We infer that their intentions were to further postpone a (next) birth or to further postpone a decision about whether to have a (next) birth.

Reproductive life course characteristics are important in predicting which women are most likely to proceed to sterilization in their years following LARC discontinuation. Notably, for women who are older and of higher parity, fertility exposure after LARC discontinuation is more likely to end with sterilization. Women who had their LARC device inserted for three or more years before its removal were also at greater risk of transitioning to sterilization. These women may have reached the end of their LARC device's life cycle (3 to 10 years, depending on LARC type) and, rather than having a new LARC inserted, decided to switch to sterilization—possibly because their decision to permanently end childbearing had crystallized.

The high predictiveness of reproductive life course readiness characteristics for giving birth or for transitioning to sterilization following LARC discontinuation, as well as the mostly lower predictiveness of socioeconomic characteristics (such as race/ethnicity and educational attainment) after reproductive life course factors are taken into account, suggest that women across social groups typically use LARC in ways that match their reproductive life course stage. Although necessarily speculative with respect to women's contraceptive motives, the profiles we estimated of women most at risk of birth, new LARC insertion, and sterilization following LARC discontinuation are consistent, respectively, with (1) using LARC to successfully transition to a birth resulting from an intended pregnancy; (2) using LARC to further postpone a birth when the initial LARC device use was discontinued after a brief time and when the woman may not yet have been ready to have another birth or to make a decision on ceasing further childbearing; and (3) using LARC to transition to a permanent method of preventing further childbearing after first deferring that decision. Taken together, our results suggest that women use LARC not only to reduce the likelihood of an unintended pregnancy but also to better time their first or next birth or as part of a trajectory toward definitively completing childbearing. That is, we find substantial evidence of LARC use for family planning purposes and not only for immediate pregnancy prevention.

Looking ahead, the composition of women who will start and subsequently discontinue use of LARC while still of reproductive age will clearly affect LARC-using women's future fertility and, in particular, their future intended fertility. This composition may change as LARC use in the United States continues to increase (Foster et al. 2015). Continued increases in LARC use among nulliparous women, as suggested in recent analyses by Kavanaugh and Jerman (2018), would then lead to greater use of LARC to optimize birth timing, thereby potentially both decreasing unintended fertility and increasing intended fertility. In contrast, future increases in LARC that are concentrated among higher-parity women—for example, by LARC acting as a substitute for, or a precursor to the use of, permanent sterilization for women who plan no future births—would likely mean that effects on intended fertility will be limited primarily to women who change their childbearing plans. However, the effects of LARC on intended fertility could still be sizable given the high current incidence of sterilization regret (Eeckhaut et al. 2018; Grimes and Mishell 2008).

Our analyses advance understanding of how continued increases in LARC use may shape U.S. (intended) fertility by helping women to follow through with their intentions regarding the timing of their first or next birth or the prevention of another birth. These findings build on previous research showing LARCs' ability to reduce contraceptive failure and unintended fertility (e.g., Winner et al. 2012) and are essential to improving our understanding of the potential broader impact of increasing LARC use on U.S. women's fertility and reproductive life courses. Considerable efforts have been undertaken in recent years to increase access to LARCs, including efforts to improve LARC supply, provider training, reimbursement, practice guidelines, and product labeling (Biggs et al. 2014; CMS 2016; Pace et al. 2016; Society of Family Planning 2010). Such efforts may advance women's reproductive autonomy by reducing common barriers to LARC use. Further research on how women use LARC to achieve their family planning goals and thereby shape their reproductive life course will also be helpful in informing providers' and policymakers' efforts such that they align well with women's contraceptive and reproductive decision-making.

Acknowledgments

We are grateful for comments received from the discussant and participants at the 2019 American Sociological Association annual meeting, and for support from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (population research infrastructure grant P2C-HD041041) and a research grant from an anonymous private philanthropic foundation.

References