[Epidemiology of spontaneous abortion: a review of the literature].

Spontaneous abortion is the commonest complication of pregnancy. Its reported incidence appears to be constant in developed countries but the frequency of subclinical fetal loss is largely unknown. There is a well known relationship between fetal loss and advancing maternal age. Trisomic fetuses occur more commonly in older women and most are aborted but old women are also at greater risk of aborting a chromosomally normal fetus. Recent epidemiological data have demonstrated a significant association between maternal cigarette smoking and spontaneous abortion. A role of gravidity, early age at menarche, alcohol and methylxanthine consumption has been recently claimed, but epidemiological evidence is scanty and largely controversial. The present paper reviews the epidemiological data on spontaneous abortion.