Spontaneous abortion and induced abortion: an adjustment for the presence of induced abortion when estimating the rate of spontaneous abortion from cross-sectional studies.

The existence of high rates of induced abortion in the population may distort currently employed measures of the rate of spontaneous abortion. Since the frequency of induced abortion varies greatly between and within populations, an appropriate correction is needed to restore the comparability of spontaneous abortion rates. A simplified estimate of the "true" rate of spontaneous abortion is proposed. This statistic yields a sufficient approximation for most purposes.