The high abortion cost of human reproduction

Abstract

Information from many large data bases and published studies was integrated to estimate the age-specific spontaneous abortion rate in an economically-developed human population. Accuracy was tested with published data from a diverse array of studies. Spontaneous abortion was found to be: i) the predominant outcome of fertilization and ii) a natural and inevitable part of human reproduction at all ages. The decision to reproduce is inextricably coupled with the production of spontaneous abortions with high probability, and the decision to have a large family leads to many spontaneous abortions with virtual certainty. The lifetime number of spontaneous abortions was estimated for a “canonical” woman (constrained to have average age at marriage, first birth, inter-birth intervals, and family size) in two populations: one with and the other without effective birth control (including free access to elective abortions). Birth control was found to reduce lifetime abortions more than 6-fold.