The identification of parity effects on the hazard of a next birth in cross-family data requires accounting for heterogeneity in fecundity across couples. In a previously published article, Cinnirella et al. Demography, 54, 413–436 (2017), we stratified duration models at the maternal level for this purpose and found that the hazard of a next birth decreases with rising parity in historical England. Clark and Cummins Demography, 56 (2019) took issue with this finding, claiming that the result is a statistical artifact caused by stratification at the maternal level. This reply documents that our previous finding is robust to addressing Clark and Cummins’ critique.