Studies about sexual health require accurate information on sexual behaviours, yet there is no gold standard for assessing sexual behaviour. Concordance of partner reports is one way to estimate the reliability and, indirectly, the validity of such data. We aimed to evaluate the inter-partner concordance of self-reported intercourse frequency among mixed-sex couples attempting conception. We analyzed data from Pregnancy Study Online (PRESTO), a North American prospective preconception cohort study. During 2013–2021, self-reported intercourse frequency at baseline was ascertained using the same question for both partners: “In the past month, about how often did you have sexual intercourse with your partner?” with categorical response options. We used unweighted and linear-weight weighted kappas to assess inter-partner concordance of reported intercourse frequency and log-binomial regression to estimate unadjusted and adjusted prevalence ratios (PR) and 95% confidence intervals (CI) for predictors of discordance. Among 3,015 couples, 1,927 (63.9%) reported exactly concordant categories of intercourse frequency, while the female partner reported more frequent intercourse in 715 (23.7%) couples and the male partner reported more frequent intercourse in 373 (12.4%) couples. Unweighted and weighted kappas were 0.50 (95% CI 0.48, 0.53) and 0.63 (95% CI 0.61, 0.65), respectively. Predictors of discordance included marital status (unmarried versus married: PR = 1.61 [95% CI 1.11, 2.29] for the male partner reporting more frequent intercourse) and longer relationship length (5–9 years, PR = 1.14 [95% CI 0.96, 1.34]; ≥ 10 years, PR = 1.14 [95% CI 0.92, 1.42], respectively, compared with < 5 years) for the female partner reporting more frequent intercourse.
