Contraceptive Method Choice Among Youth in the United States: The Importance of Relationship Context

We examine the relationship characteristics associated with contraceptive method choice within young people’s nonmarital sexual relationships, using data from retrospective relationship histories available in the third wave (2001–2002) of the National Longitudinal Study of Adolescent Health. Data-reduction techniques produce a detailed multidimensional characterization of relationship commitment for nonmarital sexual relationships. We then use multilevel analysis to estimate associations between two key relationship characteristics—relationship commitment and couple heterogamy—and the type of contraceptive method used at last sexual intercourse within each relationship. Results indicate that for a given individual, contraceptive method choice varies across relationships as a function of these characteristics, even after we account for important individual and family characteristics and prior relationship experiences.     

Sexual Activity and Weekly Contraceptive Discontinuation and Selection Among Young Adult Women in Michigan

Understanding young women’s contraceptive and pregnancy prevention behaviors is important for helping women and their partners control if and when they have children. Prior research on associations between patterns of sexual activity and contraceptive behaviors is limited. We assessed the influence of recent sexual activity on discontinuation and selection of specific contraceptive methods. We used weekly data from the Relationship Dynamics and Social Life (RDSL) study, a longitudinal 2.5-year population-based project that sampled woman ages 18 and 19 (N = 1,003) in one Michigan county. We estimated logistic and multinomial regression models that accounted for clustering of weekly observations within partnerships and women. Weekly discontinuation of longer-acting methods declined with increasing sexual activity in the past month, as did discontinuation of shorter-acting hormonal methods. Sexual activity was associated with decreased selection of condoms relative to other methods. Future research into life events that lead to changes in the frequency of sexual activity may provide insight into times when women are at risk of contraceptive discontinuation. These findings underscore the importance of anticipatory guidance in contraceptive counseling so that when women change their contraceptive behavior they are equipped in advance with resources to make safe transitions between methods.     

Effects of intensive longitudinal data collection on pregnancy and contraceptive use

We use an experiment based on the relationship dynamics and social life study of sexual behavior, pregnancy, and contraceptive use to investigate whether participation in weekly self-reports over one year result in differential effects on related behaviors and attitudes, compared to participation in a one-time follow-up interview requiring retrospective self-reporting for the prior year. We randomly assigned 200 subjects to either a control group or a journal group. All subjects were interviewed at the beginning of the study (baseline interview) and 12 months later (closeout interview). Subjects in the journal group also completed a five-minute web- or phone-based survey every week during the 12-month study period. We found no statistically significant difference in pregnancy rates across the two groups at closeout. Contrary to our expectation, the control group experienced a slightly larger increase in having ever used a contraceptive method, although this was mainly due to increases in the least effective methods, such as condoms and withdrawal. Respondents in the weekly interview group became slightly more positive toward childbearing in terms of one specific attitude measure, but not for the vast majority of measures. We conclude that intensive longitudinal data collection does not appear to have a large or consistent impact on respondents’ pregnancy, contraceptive use, or related attitudes, relative to the more standard longitudinal approach.     

Use of Biological Markers in Risk Assessment1

Measurements of intermediate end points in the carcinogenic process may reduce uncertainty in human risk assessment from bioassay data, by identifying sources of interspecies variation and dose nonlinearity. This paper describes desirable properties of such markers: persistence, predictive power, temporal relevance, and consistency across dose rate and species. We illustrate these properties by evaluating markers for squamous cell nasal carcinoma in rodents exposed to formaldehyde. We also discuss design issues for bioassays that evaluate markers and tumors simultaneously at necropsy.     

Sexual activity and weekly contraceptive use among young adult women in Michigan

Past studies on the influence of sexual activity on contraceptive behaviours are inconclusive, relying heavily on cross-sectional data. We used a population-based longitudinal sample of young women in Michigan to evaluate weekly associations between sexual activity and contraceptive use at three levels of measurement: comparing between women, among individual women’s partnerships, and from week to week within partnerships. We used multinomial logistic regression accounting for correlations within partnerships and women. Relative to use of least effective methods, weekly sexual activity was significantly associated with increased use of condoms, pills, and highly effective methods. For pills and highly effective methods, partnership-, woman-, and week-level effects were similar. For condoms, there was no significant woman-level effect. Evidence of immediate effects of sexual activity on contraceptive use highlights the importance of longitudinal data. These dynamics may be diluted or missed altogether when relying on cross-sectional data approaches that compare groups of individuals.