Births outside marriage (BoM) account for around 15% of all births globally. However, the distribution around the world is very uneven, as are cultural and political attitudes towards them. Studies from East Asia have shown that the percentage of such births is very low, with only modest increases in recent years. The orthodox demographic view holds that the maintenance of conservative views around the relationship between marriage and childbearing can play a role in keeping fertility low. Prenuptial pregnancies (PNP) (where births occur within eight months of marriage) have been identified as a growing phenomenon in Japan, possibly being an ‘alternative’ Asian pathway to family formation. As yet, no comprehensive statistical analysis of the trends of BoM or PNP has been performed for Hong Kong. Using a comprehensive microdata set of birth registration in Hong Kong from 1984–2015 (N = 1,680,831) we provide evidence of recent trends in such ‘alternative pathways’ to family formation and examine predictors through regression analysis. Our results indicate, in common with elsewhere in East Asia, low overall period rates of either BoM or PNP (although the latter has risen notably in recent years). While more recent birth cohorts exhibit higher prevalence of such births, their incomplete nature and higher expected propensity suggests that the figures are exaggerated. In our regression analysis, we find that lower educational attainment is a strong predictor of both BoM and PNP, suggesting that a bifurcation of experience may be occurring. This adds further evidence to the theory that the maintenance of traditional family formation systems in the context of revolutionised educational and work opportunities for women mean that the opportunity costs of the ‘marriage package’ become too high. Current disparities in rights and privileges between married and unmarried parents–and especially their children–means that targeted family planning services and support for vulnerable families are policy priorities.