A New Estimate of Permanent Sterility by Age

Henri F. Leridon, Institut National de la Santé et de la Recherche Médicale (INSERM)

The proportions of couples already sterile (definitely) by woman’s age have been estimated by various authors: Vincent, Henry, Trussell-Wilson, Leridon… These rates have been estimated either from the proportions of newly married couples remaining childless, or indirectly from observed distributions of ages at last live birth. This means that the level of sterility which is measured is the probability of being unable to have a live birth, not of conceiving: if a woman is unable to deliver a child after some age x, it may be because she is unable to conceive or because the pregnancy ends in a spontaneous abortion. For some applications it is unfortunate to mix up these two dimensions, the decrease of fecundability and the increase of foetal wastage when the woman (and possibly the man) gets older. We have derived new rates of sterility by age which might be later combined with the risks of spontaneous abortion.