During july 1989, we have done a retrospective study, in Koba's valley in a savanna onchocerciasis area of Mali, after a mass treatment in rural community with ivermectin. 435 women aged from 15 to 45 years, among 461 with can be submitted to ivermectin risk during their pregnancy period, was seen and overhauled. In 1987, the frequency of women who received ivermectin during their pregnancy period (treated by error), was 17.7%, and 17.3% in 1988. We have seen any difference, between exposed and not exposed women to this error ivermectin treatment, comparing their in utero-mortality, new born mortality an the level of malformations. In spite of careful clinical monitoring in the field, the risk to give ivermectin to pregnancy women in rural community, is very high during mass treatment. Because traditionally (taboos), pregnancy is a forbidden subject. Sociological and anthropological studies, pregnancy field laboratory test and health education, are needed in african rural community before mass treatment with ivermectin.