In this paper, we describe and utilize methods to estimate the consequences for children's schooling and birthweight of the exogenous variability in the supply of births in one low income country, Malaysia. The method utilizes information on contraceptive techniques employed by couples to estimate directly the technology of reproduction and provides a means of disentangling the biological and demand factors that contribute to the variation in fertility across couples under a regime of imperfect fertility control. Our results suggest that imperfect fertility control significantly influences both the average schooling attainment and birthweight of children in Malaysia, with couples having above-average propensities to conceive reporting higher levels of actual fertility, significantly lower expectations of and actual schooling attainment for their children, and lower birthweight children, on average, due to smaller intervals between births.