Sexual Intercourse Frequency During Pregnancy: Weekly Surveys Among 237 Young Women From A Random Population-Based Sample.

BACKGROUND: Significant differences in sexual frequency during pregnancy have been documented in cross-sectional and once-per-trimester longitudinal studies, with the highest sexual frequency in the first trimester and the lowest in the third trimester. However, changes in sexual frequency may be more complex than these comparisons suggest; patterns of sexual frequency have not been assessed using frequent (e.g., weekly) assessments throughout a woman's pregnancy. AIM: To assess changes in the frequency of sexual intercourse across all weeks of pregnancy. METHODS: We used data from 237 women (54% White; 43% Black) who reported a pregnancy during the Relationship Dynamics and Social Life (RDSL) study. RDSL was based on a random population-based sample of 992 women in the United States, aged 18 or 19, who completed a baseline interview and brief weekly follow-up surveys for 2.5 years. We used generalized multilevel modeling to fit and compare linear, quadratic, and piecewise (via b-splines) models. OUTCOME: Weekly probability of sexual intercourse. RESULTS: Sexual intercourse frequency clearly declined across pregnancy, yet the pattern followed the course of common pregnancy symptomology (i.e., nausea, fatigue) more closely than trimester cutoffs. The best fitting model demonstrated that the probability of sexual intercourse declined sharply (∼18% each week) between conception and 11 weeks, subsequently increased by ∼3% each week between weeks 11 and 21, and then declined steadily (∼6% each week) through the end of pregnancy. CLINICAL TRANSLATION: Documenting more precise patterns of change in sexual frequency during pregnancy provides important information to many who wish to maintain sexual intimacy while pregnant, or to those who would otherwise find the sexual disruptions particularly challenging. STRENGTHS & LIMITATIONS: This study is the first to document changes in sexual intercourse frequency throughout all weeks of pregnancy as they naturally occurred among a representative sample of young women. The focus on sexual intercourse limits the findings to only one aspect of human sexuality. The narrow age range of the sample precludes generalization to all pregnant women. CONCLUSION: Changes in sexual frequency are more complex than the general declines suggested by other studies; within-trimester patterns reveal the shortcomings in understanding sexual behavior changes when aggregated by trimester, such as severely underestimating the degree of fluctuation in the first trimester. Pregnancy symptomology may be most favorable to intercourse towards the end of the first and beginning of second trimesters, and least favorable near the end of the pregnancy. Shari M. Blumenstock, Jennifer S. Barber. Sexual Intercourse Frequency During Pregnancy: Weekly Surveys Among 237 Young Women From A Random Population-Based Sample. J Sex Med 2022;19:1524-1535.

Mechanisms Linking High Residential Mobility to Decreased Contraceptive Use: The Importance of Method Availability.

While research has demonstrated that high residential mobility has negative consequences for an array of outcomes, particularly among women and young adults, the mechanisms underlying these associations are unclear. The consequences of high residential mobility may be comprised solely of a series of short-term disruptions surrounding individual moves, or there may also be long-term, cumulative effects from repeated moves. High residential mobility may diminish access to resources as individuals move to different neighborhoods, impose a cognitive burden that impairs their ability to plan ahead, or decrease the relative power they have in their relationships to limit exposure to risk behaviors. We adjudicate between these possibilities by predicting the effects of high residential mobility on sexual intercourse and contraceptive use, the proximate determinants of pregnancy, during women's transition to adulthood. Using 2.5 years of monthly address data for 882 respondents in the Relationship Dynamics and Social Life study-a random sample of young women in Genesee County, Michigan-we find that high residential mobility is associated with long-term decreases in contraceptive use. These long-term consequences are independent of the short-term effects of individual moves and attributable to diminished contraceptive access. We disentangle the effects of home-leaving, which is distinct from subsequent moves.

How Nearby Homicides Affect Young Women's Pregnancy Desires: Evidence From a Quasi-Experiment.

Leveraging spatiotemporal variation in homicides that occurred during a 2.5-year weekly panel survey of 387 women ages 18-22 in Flint, Michigan, we investigate how young women's desires to become pregnant and to avoid pregnancy evolve in response to local homicides during the transition to adulthood. To address the endogeneity of exposure, we explore how the same woman's pregnancy desires (1) differed, on average, across weeks before and after the first homicide occurred within a quarter mile of her home; (2) evolved in the aftermath of this initial homicide exposure; and (3) changed in response to additional nearby homicides. One-fifth (22%) of women were exposed to a nearby homicide at least once during the study, and one-third of these women were exposed multiple times. Overall, the effects of nearby homicides were gradual: although average desires to become pregnant and to avoid pregnancy differed after initial exposure, these differences emerged approximately three to five months post-exposure. Repeated exposure to nearby homicides had nonlinear effects on how much women wanted to become pregnant and how much they wanted to avoid pregnancy. Together, our analyses provide a new explanation for why some young women-especially those who are socially disadvantaged-desire pregnancy at an early age.

Black-White Differences in Pregnancy Desire During the Transition to Adulthood.

This article explores race differences in the desire to avoid pregnancy or become pregnant using survey data from a random sample of 914 young women (ages 18-22) living in a Michigan county and semi-structured interviews with a subsample of 60 of the women. In the survey data, desire for pregnancy, indifference, and ambivalence are very rare but are more prevalent among Black women than White women. In the semi-structured interviews, although few women described fatalistic beliefs or lack of planning for future pregnancies, Black and White women did so equally often. Women more often described fatalistic beliefs and lack of planning when retrospectively describing their past than when prospectively describing their future. Using the survey data to compare prospective desires for a future pregnancy with women's recollections of those desires after they conceived, more Black women shifted positive than shifted negative, and Black women were more likely to shift positive than White women-that is, Black women do not differentially retrospectively overreport prospectively desired pregnancies as having been undesired before conception. Young women's consistent (over repeated interviews) prospective expression of strong desire to avoid pregnancy and correspondingly weak desire for pregnancy, along with the similarity of Black and White women's pregnancy plans, lead us to conclude that a "planning paradigm"-in which young women are encouraged and supported in implementing their pregnancy desires-is probably appropriate for the vast majority of young women and, most importantly, is similarly appropriate for Black and White young women.

The Dynamics of Intimate Relationships and Contraceptive Use During Early Emerging Adulthood.

We investigate the immediate social context of contraceptive behaviors: specifically, the intimate relationship. We use the Relationship Dynamics and Social Life (RDSL) study (2008-2012), based on a random sample of 1,003 women ages 18-19 residing in a Michigan county. Women were interviewed weekly for 2.5 years, resulting in an age range of 18-22. We test three sets of hypotheses about change over time within a relationship, using relationship-level within-between models, which compare a couple's contraceptive behaviors across different times in the relationship. First, we find that a couple is less likely to use contraception when the relationship is more intimate and/or committed and that a couple becomes less likely to use contraception over time, regardless of intimacy and commitment. Second, we find that a couple using contraception becomes increasingly likely to choose hormonal over coital methods, but this change occurs as a relationship endures and is unrelated to intimacy and/or commitment. Third, we find that a condom-using couple's consistency does not decline when there is conflict; rather, consistency of condom use declines over time regardless of the relationship's characteristics. We also demonstrate that conflict and power imbalance increase reliance on hormonal methods among those using contraception; conflict decreases consistency among withdrawal (but not condom) users; and nonmonogamy increases reliance on condoms and decreases withdrawal consistency. The strong and consistent link between duration and contraceptive behaviors-regardless of intimacy, commitment, conflict, or power imbalance-suggests that the continual vigilance required for long-term contraceptive use is difficult during early emerging adulthood.

Sexual Concurrency and Contraceptive Use Among Young Adult Women.

Leveraging 2.5 years of weekly data from the Relationship Dynamics and Social Life Study, we investigate the relationship between young women's sexual concurrency and their contraceptive behavior. Specifically, we (1) examine whether young women changed their contraceptive use when switching from one to multiple concurrent sexual partners in the same week; (2) explore the uniformity of contraceptive responses to concurrency across relationship context; and (3) compare the contraceptive behaviors of never-concurrent women with those of ever-concurrent women in weeks when they were not concurrent. Nearly one in five sexually active young women had sex with two or more people in the same week. When they were concurrent, these women's odds of using any contraception increased threefold, and their odds of using condoms increased fourfold. This pattern of contraceptive adjustments was the same across relationship characteristics, such as duration and exclusivity. Yet when they were not concurrent, ever-concurrent women were less likely to use any contraception and used condoms less consistently than women who were never concurrent. We discuss these findings in the context of ongoing debates about the role of sexual concurrency in STI transmission dynamics.

Dimensions of Reproductive Attitudes and Knowledge Related to Unintended Childbearing Among U.S. Adolescents and Young Adults.

Measures of attitudes and knowledge predict reproductive behavior, such as unintended fertility among adolescents and young adults. However, there is little consensus as to the underlying dimensions these measures represent, how to compare findings across surveys using different measures, or how to interpret the concepts captured by existing measures. To guide future research on reproductive behavior, we propose an organizing framework for existing measures. We suggest that two overarching multidimensional concepts-reproductive attitudes and reproductive knowledge-can be applied to understand existing research using various measures. We adapt psychometric analytic techniques to analyze two data sets: the National Longitudinal Survey of Adolescent to Adult Health (Add Health) and the Relationship Dynamics and Social Life study (RDSL). Although the specific survey measures and sample composition of the two data sets are different, the dimensionality of the concepts and the content of the items used to measure their latent factors are remarkably consistent across the two data sets, and the factors are predictive of subsequent contraceptive behavior. However, some survey items do not seem strongly related to any dimension of either construct, and some dimensions of the two concepts appear to be poorly measured with existing survey questions. Nonetheless, we argue that the concepts of reproductive attitudes and reproductive knowledge are useful for categorizing and analyzing social psychological measures related to unintended fertility. The results can be used to guide secondary data analyses to predict reproductive behavior, compare results across data sets, and structure future data collection efforts.

MEDIATION MODELS OF PREGNANCY DESIRES AND UNPLANNED PREGNANCY IN YOUNG, UNMARRIED WOMEN.

This paper examines the proposition that sexual and contraceptive behaviours mediate the relationship between the pregnancy desires of young, unmarried women and their having an unplanned pregnancy. The sample consisted of 854 18- to 19-year-old women living in Michigan, USA. First, the positive and negative pregnancy desires of these women were measured, as were the women's perceptions of the positive and negative desires of their sexual partners. Then the extent to which these four types of desires, as well as several types of interactions between them, prospectively predicted the occurrence of subsequent pregnancies were tested with logistic regression analyses, initially alone and then after the addition of several types of sexual and contraceptive mediator variables. The results demonstrated that four of the ten significant motivational predictors became non-significant following the introduction of the contraceptive mediator variables and that the predictive strength of the other six significant motivational predictors was substantially reduced by their introduction. A number of factors that may account for only a partial mediational effect in some models are discussed.

The Dynamics of Intimate Partner Violence and the Risk of Pregnancy during the Transition to Adulthood.

Using a reproductive coercion framework, we investigate the role of intimate partner violence (IPV) in pregnancy during the transition to adulthood. We use two types of data from a population-based sample of 867 young women in a Michigan county: a 60-minute survey interview with 2.5 years of weekly follow-up surveys, and semi-structured interviews with a subsample of 40 pregnant women. The semi-structured interviews illustrate the violence women experienced. Discrete-time logit hazard models demonstrate that threats and physical assault are associated with higher pregnancy rates during ages 18 to 22. However, this holds only when the violence is recent; violence occurring more than a month earlier is not associated with higher pregnancy rates. These associations are independent of violent experiences with prior partners, which are also associated with higher pregnancy rates. Fixed-effects models show that during violent weeks, women perceive more pregnancy desire from their partners, have more sex, and use less contraception than during nonviolent weeks. Finally, mediation analyses and the semi-structured interviews are consistent with reproductive coercion: violent young men are more likely to want their girlfriends pregnant, and they use threats and physical assault to implement their preferences via sex and contraceptive non-use, which in turn increase pregnancy rates.

Do perceptions of their partners' childbearing desires affect young women's pregnancy risk? Further study of ambivalence.

We explore whether young women's perceptions of their sexual partners' childbearing desires contribute to their risk of pregnancy. We used weekly journal data collected from 787 young women to measure their childbearing desires and their perceptions of their partners' childbearing desires. We then conducted hazard modelling to predict pregnancy risk with variables based on interactions between the women's desires and their perceived partners' desires. Models that include perceived partners' desires perform better than one based on women's desires alone. The best model contains three significant predictors: one confirms the importance of pronatal, ambivalent, and indifferent desires for pregnancy risk; one indicates that the perceived partners' antinatal desires reduce women's pregnancy risk; and one suggests that women who both perceive their partners accurately and are in agreement with them have a lower pregnancy risk. The results indicate that perceived partner data can improve prediction and enhance our understanding of pregnancy risk.

Black-White Differences in Sex and Contraceptive Use Among Young Women.

This study examines black-white and other sociodemographic differences in young women's sexual and contraceptive behaviors, using new longitudinal data from a weekly journal-based study of 1,003 18- to 19-year-old women spanning 2.5 years. We investigate hypotheses about dynamic processes in these behaviors during early adulthood in order to shed light on persisting racial differences in rates of unintended pregnancies in the United States. We find that net of other sociodemographic characteristics and adolescent experiences with sex and pregnancy, black women spent less time in relationships and had sex less frequently in their relationships than white women, but did not differ in the number of relationships they formed or in their frequency or consistency of contraceptive use within relationships. Black women were more likely to use less effective methods for pregnancy prevention (e.g., condoms) than white women, who tended to use more effective methods (e.g., oral contraceptives). And although the most effective method for pregnancy prevention-long-acting reversible contraception (LARC)-was used more often by black women than white women, LARC use was low in both groups. In addition, black women did not differ from white women in their number of discontinuations or different methods used and had fewer contraceptive method switches. Further, we find that net of race and adolescent experiences with sex and pregnancy, women from more-disadvantaged backgrounds had fewer and longer (and thus potentially more serious) relationships, used contraception less frequently (but not less consistently), and used less effective methods (condoms) than women from more-advantaged backgrounds.

Participation in an Intensive Longitudinal Study with Weekly Web Surveys Over 2.5 Years.

BACKGROUND: Technological advances have made it easier for researchers to collect more frequent longitudinal data from survey respondents via personal computers, smartphones, and other mobile devices. Although technology has led to an increase in data-intensive longitudinal studies, little is known about attrition from such studies or the differences between respondents who complete frequently administered surveys in a timely manner, and respondents who do not. OBJECTIVE: We examined respondent characteristics and behaviors associated with continued and on-time participation in a population-based intensive longitudinal study, using weekly web-based survey interviews over an extended period. METHODS: We analyzed data from the Relationship Dynamics and Social Life study, an intensive longitudinal study that collected weekly web-based survey interviews for 2.5 years from 1003 18- and 19-year-olds to investigate factors shaping the dynamics of their sexual behavior, contraceptive use, and pregnancies. RESULTS: Ordinary least squares and logistic regression analyses showed background respondent characteristics measured at baseline were associated with the number of days respondents remained enrolled in the study, the number of interviews they completed, and the odds that they were late completing interviews. In addition, we found that changes in pregnancy-related behaviors reported in the weekly interviews were associated with late completion of interviews. Specifically, after controlling for sociodemographic, personality, contact information, and prior experience variables, we found that weekly reports such as starting to have sex (odds ratio [OR] 1.17, 95% CI 1.03-1.32, P=.01), getting a new partner (OR 1.76, 95% CI 1.53-2.03, P<.001), stopping the use of contraception (OR 1.28, 95% CI 1.10-1.49, P=.001), and having a new pregnancy (OR 5.57, 95% CI 4.26-7.29, P<.001) were significantly associated with late survey completion. However, young women who reported changes in pregnancy-related behaviors also had lower levels of study attrition, and completed more interviews overall, than did their counterparts. CONCLUSIONS: We found that measures of participation in a longitudinal study with weekly web surveys varied not only by respondent characteristics, but also by behaviors measured across the surveys. Our analyses suggest that respondents who experience the behaviors measured by the study may maintain higher participation levels than respondents who do not experience those behaviors.

Sexual Behavior and Contraceptive Use among 18- to 19-Year-Old Adolescent Women by Weight Status: A Longitudinal Analysis.

OBJECTIVE: To describe the association between weight status and sexual practices among 18- to 19-year-old women. STUDY DESIGN: We analyzed a population-based longitudinal study of 18- to 19-year-old women residing in a Michigan county at cohort inception. Weekly journal surveys measured sexual practices, including contraceptive behaviors. Outcomes included proportion of weeks with a partner, proportion of weeks with sexual intercourse, number of partners, average length of relationships, proportion of weeks with contraception use, and proportion of weeks where contraception was used consistently. We examined 26,545 journal surveys from 900 women over the first study year. Ordinary least squares regression models for each outcome examined differences by weight status, controlling for sociodemographic characteristics. RESULTS: The mean proportion of weeks in which adolescents reported sexual intercourse was 52%; there was no difference by weight status. Among weeks in which adolescents reported sexual activity, obese adolescents had a lower proportion of weeks where any contraception was used compared with normal weight adolescents (84% vs 91%, P = .011). Among weeks in which adolescents reported sexual activity and contraceptive use, obese adolescents had a lower proportion of weeks with consistent contraceptive use (68% vs 78%, P = .016) and oral contraceptive pill use (27% vs 45%, P = .001) compared with normal weight adolescents. All other relationships by weight status were not statistically significant. CONCLUSIONS: In this longitudinal study, obese adolescent women were less likely to use contraception, and less likely to use it consistently when compared with normal weight peers. Findings suggest obesity may be an important factor associated with adolescent women's sexual behavior.

A systematic review and meta-analysis of thiazide-induced hyponatraemia: time to reconsider electrolyte monitoring regimens after thiazide initiation?

AIMS: Hyponatraemia is one of the major adverse effects of thiazide and thiazide-like diuretics and the leading cause of drug-induced hyponatraemia requiring hospital admission. We sought to review and analyze all published cases of this important condition. METHODS: Ovid Medline, Embase, Web of Science and PubMed electronic databases were searched to identify all relevant articles published before October 2013. A proportions meta-analysis was undertaken. RESULTS: One hundred and two articles were identified of which 49 were single patient case reports. Meta-analysis showed that mean age was 75 (95% CI 73, 77) years, 79% were women (95% CI 74, 82) and mean body mass index was 25 (95% CI 20, 30) kg m(-2) . Presentation with thiazide-induced hyponatraemia occurred a mean of 19 (95% CI 8, 30) days after starting treatment, with mean trough serum sodium concentration of 116 (95% CI 113, 120) mm and serum potassium of 3.3 (95% CI 3.0, 3.5) mm. Mean urinary sodium concentration was 64 mm (95% CI 47, 81). The most frequently reported drugs were hydrochlorothiazide, indapamide and bendroflumethiazide. CONCLUSIONS: Patients with thiazide-induced hyponatraemia were characterized by advanced age, female gender, inappropriate saliuresis and mild hypokalaemia. Low BMI was not found to be a significant risk factor, despite previous suggestions. The time from thiazide initiation to presentation with hyponatraemia suggests that the recommended practice of performing a single investigation of serum biochemistry 7-14 days after thiazide initiation may be insufficient or suboptimal. Further larger and more systematic studies of thiazide-induced hyponatraemia are required.

Young women's perceptions and experiences with contraception supply in community pharmacies.

BACKGROUND: Unintended pregnancy is a major public health problem in the United States.Correct contraceptive use can reduce the rate of unintended pregnancy. Community pharmacies are well positioned to provide contraceptives and advice about contraception. OBJECTIVES: To determine young women's perceptions and experiences with contraception supply in community pharmacies and to identify whether pharmacy characteristics predicted very positive experiences. DESIGN: This study comprised two cross-sectional surveys including an online women's pharmacy perceptions and experiences (PPE) survey and a faxed/observed survey of community pharmacies. SETTING: One county in Michigan. PARTICIPANTS: Young women and community pharmacies. MAIN OUTCOME MEASURE: The two surveys were merged to explore pharmacy characteristics that may impact women's perceptions and experiences with community pharmacies. Multiple logistic regression analysis was used to explore relationships between pharmacy characteristics and positive outcomes. RESULTS: The response rate for the PPE survey was 54% (n = 343/637). Data from all community pharmacies in the county was retrieved via fax (n = 41/94, 43.6%) or observation (n = 53/94, 56.4%). Women were included in this analysis if they indicated a regular pharmacy (one they go to most often) in the county of interest (n = 210). More than 50% of women (n = 125/210) visited a pharmacy more than once per month. Sixty percent of women were currently using something to prevent pregnancy (n = 124/210, 60.8%). Thirty-five percent of women had a positive experience (n = 73/210, 34.8%). In the multiple logistic regression, women who visited a chain pharmacy had almost 65% lower odds of an overall positive experience with their regular pharmacy compared with women who visited a grocery or mass merchandise pharmacy (odds ratio 0.35 [95% CI 0.16], P = 0.75). CONCLUSION: Young women visit community pharmacies and use contraceptives frequently. Interventions need to be developed and implemented to improve young women's perceptions and experiences with contraception at community pharmacies.

Stress symptoms and frequency of sexual intercourse among young women.

INTRODUCTION: We have previously documented the relationships between stress and depression symptoms and adolescent women's nonuse and misuse of condoms and other contraceptive methods and on their unintended pregnancy rates. AIM: Here, we examine relationships between mental health symptoms and another understudied adolescent reproductive health behavior-frequency of sexual intercourse. MAIN OUTCOME MEASURE: Our outcome was weekly sexual intercourse activity. METHODS: We used panel data from a longitudinal, population-based cohort study of 992 women ages 18-20. Weekly journals measured sociodemographic, relationship, reproductive, and mental health characteristics, sexual and contraceptive behaviors, and pregnancy history. We examined 27,130 surveys from 952 women during the first study year. Predictors of weekly sexual intercourse were moderate to severe stress (Perceived Stress Scale-4) and depression (Center for Epidemiologic Studies Depression Scale-5) symptoms measured at baseline. Multilevel, mixed-effects logistic regression models estimated the relationships between stress and depression symptoms and the weekly odds of sexual intercourse while adjusting for covariate fixed effects and random woman effects. RESULTS: Nearly a quarter of the sample had moderate to severe stress (23%) and depression (24%) symptoms at baseline. Women reported sexual intercourse in 36% of weeks. Proportions of sexually active weeks were higher among women with stress (43%) and depression (40%) compared with those without symptoms (35% and 35%, respectively; P values<0.001). Controlling for covariates, women with baseline stress symptoms had 1.6 times higher weekly odds of sexual intercourse compared with women without stress (adjusted odds ratio 1.6, confidence interval [1.1, 2.5]; P=0.04). Depression symptoms were not associated with sexual intercourse frequency in adjusted models. CONCLUSIONS: Stress symptoms were positively associated with sexual intercourse frequency among these young women. Research and practice efforts are needed to identify effective sexual health promotion and risk-reduction strategies, including contraceptive education and counseling, in the context of mental health symptoms and unintended pregnancy.

Pregnancy scares and subsequent unintended pregnancy.

BACKGROUND: A substantial number of young women experience pregnancy scares - thinking they might be pregnant, and later discovering that they are not. Although pregnancy scares are distressing events, little is known about who experiences them and whether they are important to our understanding of unintended pregnancy. OBJECTIVE: We describe the young women who experience pregnancy scares, and examine the link between pregnancy scares and subsequent unintended pregnancy. METHODS: We used data from the Relationship Dynamics and Social Life Study. T-tests and regression analyses were conducted using baseline and weekly data to estimate relationships between respondent characteristics and subsequent pregnancy scares. Event history methods were used to assess pregnancy scares as a predictor of unintended pregnancy. RESULTS: Nine percent of the young women experienced a pregnancy scare during the study. African-American race, lack of two-parent family structure, lower GPA, cohabitation, and sex without birth control prior to the study are associated with experiencing a pregnancy scare and with experiencing a greater number of pregnancy scares. Further, experiencing a pregnancy scare is strongly associated with subsequent unintended pregnancy, independent of background factors. Forty percent of the women who experienced a pregnancy scare subsequently had an unintended pregnancy during the study period, relative to only 11% of those who did not experience a pregnancy scare. CONCLUSIONS: Young women from less advantaged backgrounds are more likely to experience a pregnancy scare, and pregnancy scares are often followed by an unintended pregnancy.

The effects of ambivalent fertility desires on pregnancy risk in young women in the USA.

Many different definitions of the construct of motivational ambivalence have appeared in the literature on reproductive health. Using a theoretical framework in which motivational ambivalence is defined as an interaction between positive and negative pregnancy desires, we propose two hypotheses. The first is that positive and negative pregnancy desires independently predict the risk of an unplanned pregnancy. The second is that ambivalence and three related constructs that are also based on the interaction between positive and negative desires are each important predictors of pregnancy risk. We use weekly journal data collected from a US sample of 1,003 women aged 18-19 years and conduct hazard model analysis to test our hypotheses. Using both dummy and continuous predictors, we report results that confirm both hypotheses. The proposed interaction framework has demonstrated validity, compares favourably with previously reported alternative approaches, and incorporates a set of constructs that have potential importance for further research directed at the prevention of unplanned pregnancy.

Hormonal Contraception Use and Sexual Frequency across Young Women's Intimate Relationships.

We examined whether hormonal contraception (HC) use predicts sexual frequency throughout and across young women's intimate relationships. From 2008-2012, the Relationships Dynamics and Social Life Study collected weekly surveys over 2.5 years, and included 893 women (aged 18-19 at baseline) who reported 2,547 intimate relationships across 32,736 weeks. Three-level logistic multilevel models assessed the weekly probability of sexual intercourse based on 1) weekly HC use (vs. nonuse) and 2) duration of HC use, both accounting for several relational and individual characteristics, including relationship duration. Women had more frequent sexual intercourse when they were using HC than when they were not (predicted probabilities .65 vs .41). The weekly probability of sexual intercourse increased sharply within the first month of HC initiation (by about 27 percentage points), remained high for several months, then began to slowly decline (yet remained above that of nonuse). When separated by method type, similar trajectories were found for the pill, ring, and IUD/implant; following the initial increase, steeper declines in intercourse frequency were found for the contraceptive injectable, eventually dropping below pre-initiation levels. Findings signify the immediate influence of reduced pregnancy fears in facilitating sexual intercourse among young women, which may decline as HC use continues long-term.

The Dynamics of Intimate Relationships and Violent Victimization Among Young Women.

Despite the fact that intimate partner violence (IPV) occurs within intimate relationships, we know relatively little about the characteristics of those intimate relationships, and even less about how IPV changes across time within different relationships. We use the Relationship Dynamics and Social Life (RDSL) study, based on a random sample of 1003 18-19-year-old women residing in a Michigan county. Women were interviewed weekly for 2.5 years, resulting in an age range of 18 through 22. We estimate hybrid "within-between" regression models, which allows us to directly compare the same woman's risk of experiencing IPV across her different relationships, varied in terms of resources, balance of power, conflict, childbearing, relationship type, and duration. Our analyses demonstrate that power imbalance in intimate relationships, non-monogamous and unstable relationships, relationships with men who are not the father of a woman's existing children, and serious relationships (especially stayover and cohabiting) place young women in their late teens and early twenties at particularly high risk of multiple dimensions of IPV. Our fixed-effects modeling strategy isolated the increase in IPV risk that is due to these characteristics and experiences within intimate relationships from the risk due to young women being at high risk of IPV for other reasons who might tend to choose these types of relationships. The elevated risk of IPV in relationships with these characteristics and experiences supports a causal link between them. Our research supports the potential efficacy of interventions that reduce conflict, equalize power within relationships, and encourage women-especially young mothers-to delay serious relationships.