Despite the heightened interest in human reproduction and the significant implications of premarital pregnancy for children's health, strikingly little research has paid attention to the determinants or premarital pregnancy compared with more conventional fertility behavior. To fill this gap in the literature, this study drew data from the Korean Longitudinal Survey of Women and Families (N=4333) and estimated discrete-time event history models using multinomial logistic regressions. Results from descriptive analyses indicate that the share of premarital pregnancy among all births registered increased roughly two and a half times between 1997 and 2014. Also, while premarital conception increased in women at all educational levels, high school graduates and those with less than an elementary school education showed the largest increase in the share of premarital pregnancy. The results from multivariate models suggest that the characteristics of the women's family of origin, such as being the firstborn child, the mother's education, their living arrangements during adolescence, and their region of residence have enduring effects on both premarital and post-martial pregnancy. Women's achieved socioeconomic status, however, showed a weaker effect on the odds of premarital pregnancy than expected. The predicted probabilities of premarital pregnancy by age at first marriage across birth cohorts born between the 1940s and 1970s suggest that premarital pregnancy is particularly pronounced among women who marry in their early twenties. Moreover, at a given age at first marriage, the predicted probability of premarital pregnancy monotonically increases in more recent birth cohorts, suggesting that bridal pregnancy is increasingly prevalent among modern Korean women.