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Abstract BackgroundThe target trial framework was developed as a strategy to design and analyze observational epidemiologic studies with the aim of reducing bias due to analytic decisions. It involves designing a hypothetical randomized trial to answer a question of interest and systematically considering how to use observational data to emulate each trial component. AimsThe primary aim of this paper is to provide a detailed example of the application of the target trial framework to a research question in oral epidemiology. Materials and MethodsWe describe the development of a hypothetical target trial and emulation protocol to evaluate the effect of preconception periodontitis treatment on time‐to‐pregnancy. We leverage data from Pregnancy Study Online (PRESTO), a preconception cohort, to ground our example in existing observational data. We discuss the decision‐making process for each trial component, as well as limitations encountered. ResultsOur target trial application revealed data limitations that precluded us from carrying out the proposed emulation. Implications for data quality are discussed and we provide recommendations for researchers interested in conducting trial emulations in the field of oral epidemiology. DiscussionThe target trial framework has the potential to improve the validity of observational research in oral health, when properly applied. ConclusionWe encourage the broad adoption of the target trial framework to the field of observational oral health research and demonstrate its value as a tool to identify directions for future research. 

ObjectivesTo evaluate the association between preconception contraceptive use and miscarriage. DesignProspective cohort study. SettingResidents of the United States of America or Canada, recruited from 2013 until the end of 2022. Participants13 460 female identified participants aged 21-45 years who were planning a pregnancy were included, of whom 8899 conceived. Participants reported data for contraceptive history, early pregnancy, miscarriage, and potential confounders during preconception and pregnancy. Main outcome measureMiscarriage, defined as pregnancy loss before 20 weeks of gestation. ResultsPreconception use of combined and progestin-only oral contraceptives, hormonal intrauterine devices, copper intrauterine devices, rings, implants, or natural methods was not associated with miscarriage compared with use of barrier methods. Participants who most recently used patch (incidence rate ratios 1.34 (95% confidence interval 0.81 to 2.21)) or injectable contraceptives (1.44 (0.99 to 2.12)) had higher rates of miscarriage compared with recent users of barrier methods, although results were imprecise due to the small numbers of participants who used patch and injectable contraceptives. ConclusionsUse of most contraceptives before conception was not appreciably associated with miscarriage rate. Individuals who used patch and injectable contraceptives had higher rates of miscarriage relative to users of barrier methods, although these results were imprecise and residual confounding was possible. 

Abstract BackgroundPsychological stress is prevalent among reproductive‐aged men. Assessment of semen quality for epidemiological studies is challenging as data collection is expensive and cumbersome, and studies evaluating the effect of perceived stress on semen quality are inconsistent. ObjectiveTo examine the association between perceived stress and semen quality. Material and methodsWe analyzed baseline data on 644 men (1,159 semen samples) from two prospective preconception cohort studies during 2015–2021: 592 in Pregnancy Study Online (PRESTO) and 52 in SnartForaeldre.dk (SF). At study entry, men aged ≥21 years (PRESTO) and ≥18 years (SF) trying to conceive without fertility treatment completed a questionnaire on reproductive and medical history, socio‐demographics, lifestyle, and the 10‐item version of the Perceived Stress Scale (PSS; interquartile range [IQR] of scores: 0–40). After enrollment (median weeks: 2.1, IQR: 1.3–3.7), men were invited to perform in‐home semen testing, twice with 7–10 days between tests, using the Trak Male Fertility Testing System. Semen quality was characterized by semen volume, sperm concentration, and total sperm count. We fit generalized estimating equation linear regression models to estimate the percent difference in mean log‐transformed semen parameters by four PSS groups (<10, 10–14, 15–19, ≥20), adjusting for potential confounders. ResultsThe median PSS score and IQR was 15 (10–19), and 136 men (21.1%) had a PSS score ≥20. Comparing men with PSS scores ≥20 with <10, the adjusted percent difference was −2.7 (95% CI: −9.8; 5.0) for semen volume, 6.8 (95% CI: ‐10.9; 28.1) for sperm concentration, and 4.3 (95% CI: −13.8; 26.2) for total sperm count. ConclusionOur findings indicate that perceived stress is not materially associated with semen volume, sperm concentration, or total sperm count. 

Abstract Objective To evaluate the association between pregravid use of a variety of contraceptive methods and subsequent fecundability. Design Prospective cohort study. Setting Denmark and North America, 2007-19. Participants 17 954 women who had tried to conceive for up to six menstrual cycles at study entry. At baseline, participants reported their contraceptive histories, and personal, medical, and lifestyle characteristics. Main outcome measures Pregnancy, determined by bimonthly follow-up questionnaires for up to 12 months. Results Approximately 38% (n=6735) of participants had recently used oral contraceptives, 13% (n=2398) had used long acting reversible contraceptive methods, and 31% (n=5497) had used barrier methods. Women who had recently stopped using oral contraceptives, the contraceptive ring, and some long acting reversible contraceptive methods experienced short term delays in return of fertility compared with users of barrier methods. Use of injectable contraceptives was associated with decreased fecundability compared with use of barrier methods (fecundability ratio 0.65; 95% confidence interval 0.47 to 0.89). Users of injectable contraceptives had the longest delay in return of normal fertility (five to eight menstrual cycles), followed by users of patch contraceptives (four cycles), users of oral and ring contraceptives (three cycles), and users of hormonal and copper intrauterine devices and implant contraceptives (two cycles). Lifetime length of use of hormonal contraceptive methods was not associated with fecundability. Conclusions Use of some hormonal contraceptive methods was associated with delays in return of fertility, with injectable contraceptives showing the longest delay. The findings indicated little or no lasting effect of long term use of these methods on fecundability. 

Abstract Some reproductive-aged individuals remain unvaccinated against coronavirus disease 2019 (COVID-19) because of concerns about potential adverse effects on fertility. Using data from an internet-based preconception cohort study, we examined the associations of COVID-19 vaccination and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with fertility among couples trying to conceive spontaneously. We enrolled 2,126 self-identified female participants aged 21–45 year residing in the United States or Canada during December 2020–September 2021 and followed them through November 2021. Participants completed questionnaires every 8 weeks on sociodemographics, lifestyle, medical factors, and partner information. We fit proportional probabilities regression models to estimate associations between self-reported COVID-19 vaccination and SARS-CoV-2 infection in both partners with fecundability (i.e., the per-cycle probability of conception), adjusting for potential confounders. COVID-19 vaccination was not appreciably associated with fecundability in either partner (female fecundability ratio (FR) = 1.08, 95% confidence interval (CI): 0.95, 1.23; male FR = 0.95, 95% CI: 0.83, 1.10). Female SARS-CoV-2 infection was not strongly associated with fecundability (FR = 1.07, 95% CI: 0.87, 1.31). Male infection was associated with a transient reduction in fecundability (for infection within 60 days, FR = 0.82, 95% CI: 0.47, 1.45; for infection after 60 days, FR = 1.16, 95% CI: 0.92, 1.47). These findings indicate that male SARS-CoV-2 infection may be associated with a short-term decline in fertility and that COVID-19 vaccination does not impair fertility in either partner.