We use the natural experiment of first birth twins to estimate the effects of changes in fertility on the nutritional status and school enrollment of children in Romania, a country with a unique fertility history. Estimates indicate that increases in the number of children have negative impacts on children’s human capital investments that are considerably larger than those obtained without controlling for the endogeneity of fertility. We infer that harsh pronatalist polices prior to the 1989 Revolution had adverse consequences for the human capital of Romanian children, and conversely that policies that make fertility control easier will have significant positive impacts on children’s human capital.