“Can We Wait until the Early 30s?” Some Results on the Effect of Age on the Probability to Have a First Child

John W. McDonald, University of Southampton
Ester Rizzi, Università di Padova
Alessandro Rosina, Università Cattolica

One of the limits of previous studies of "How late can you wait?" is the difficulty of controlling for sexual behaviour. McDonald and Rosina (2002) analysed Hutterite fecundability using marriage duration as a proxy for coital frequency and disentangled the effects of covariates on sterility and on conditional fecundability (i.e. the probability of conception given that the couple is not sterile). Conditional fecundability is related with marriage duration, while sterility is significantly reduced in the second half of 30s. Dunson et al. (2002) use data on timing of intercourse. They find that fecunability declines in the late 20s with substantial decreases by the late 30s. Using the same data, we focus on the probability of a first pregnancy for women 20-34 years old. In our model we try to evaluate the effect of age trying to take into account primary sterility, and to control for frequency and timing of intercourse.