[Epidemiologic aspects of extrauterine pregnancy]

Looking over the last twenty years, the increase in the numbers of ectopic pregnancies has become an important health issue. It is necessary to find out the principal causes for the rise if preventive action is to be taken. Different publications have widely different views about the incidence of the condition and how the increase came about. This variation is due to the diversity of the places and of the different populations that have been studied (age, the way the populations were recruited) as well as the frequencies that have been calculated (according to the number of pregnancies, according to the number of deliveries or according to the number of women of reproductive age in a population). All the same, the trend can be noted. These are: the doubling or tripling in the last two decades of the incidence in industrialised countries. The results of certain epidemiological studies undertaken to seek out the risk factors (mainly based on case histories) have to be interpreted carefully because of the differences in methodology and particularly in the choice of control groups (there seems to be some failure to take into account confounding factors). The chief of the risk factors for extra-uterine pregnancy which are now considered important are the increase in sexually transmitted diseases and in particular in Chlamydia trachomatis. The role played by tubal sterilisation and by some contraceptive measures such as intra-uterine contraceptive device and the progestational mini-pill in the causation of extra-uterine pregnancy can be explained by the fact that these methods are better at preventing intra-uterine pregnancy than extra-uterine pregnancy, although they to diminish the risk of these as well. Furthermore, spontaneous abortions, abdominal surgery and, above all, terminations of pregnancy which had been said to be conductive to the causation of extra-uterine pregnancies, seem to do this by the fact that they are associated with pelvic inflammatory disease. Finally, the role of in vitro fertilisation, and of vaginal irrigation, as well as of nicotine, should be sought out when further studies are carried out.