It is well known that childbearing is ‘associated’ with other life course processes like partnership and employment. However, there is very little research that studies the causal links between these processes. We study a birth cohort of women who were born in the UK in 1970, and demonstrate a new approach for the analysis of causally interrelated family events. This approach uses the g-formula, an advanced method for causal inference, to examine the causal links between employment, partnership, socio-economic status and fertility, while also controlling for important factors like age and education. Our results show that a significant reduction in fertility rates would be caused by a reduction in marriage rates, and to a lesser extent by a rise in full-time employment immediately after giving birth. However, after taking account of causal mediation, we find no impact of parental socio-economic status on fertility under plausible scenarios of upward social mobility.