A cross-sectional analytical study of geophagia practices and blood metal concentrations in pregnant women in Johannesburg, South Africa

Background. Geophagia, a form of pica, has been shown to be widely practised in sub-Saharan Africa, especially among pregnant women. Objective. To assess the prevalence of geophagia and examine exposure to selected metals and associated risk factors in women attending an antenatal clinic at Rahima Moosa Mother and Child Hospital, Johannesburg, South Africa, during June and July 2010. Methods. We conducted a cross-sectional study on a convenience sample of 307 pregnant women, ranging in age from 18 to 46 years. Structured interviews were conducted to understand geophagia practices. Blood samples were collected to determine haemoglobin values and concentrations of arsenic, cadmium, mercury and lead. Statistical analyses using the χ² test, Wilcoxon's rank-sum test and logistic regression analyses were performed as appropriate. Results. Mean parity was 1.4 and the mean (standard deviation) gestational age 30.3 (6.0) weeks. Geophagia was reported by 60 women (19.5%), and the majority purchased soil from street vendors (83.3%). The prevalence of anaemia in the study sample was 16.9% (95% confidence interval 13.1 - 21.6%). Geophagic women had significantly higher blood lead levels than non-geophagic women (2.1 v. 1.4 μg/dl; p<0.001). Anaemia, the use of African traditional medicines and craving of non-nutritive substances in a previous pregnancy were associated with geophagia. Conclusions. Geophagia is practised by a considerable proportion of pregnant women in Johannesburg, especially migrant women. Greater vigilance in respect of pica, especially geophagia, may be needed as part of antenatal care programmes to avoid potentially detrimental health effects of the practice.