Child marriage (including union or cohabitation)[91] is defined as marriage under the age of eighteen and is an ancient custom. In 2010 it was estimated that 67 million women, then, in their twenties had been married before they turned eighteen, and that 150 million would be in the next decade, equivalent to 15 million per year. This number had increased to 70 million by 2012. In developing countries one third of girls are married under age, and 1:9 before 15.[92] The practice is commonest in South Asia (48% of women), Africa (42%) and Latin America and the Caribbean (29%). The highest prevalence is in Western and Sub-Saharan Africa. The percentage of girls married before the age of eighteen is as high as 75% in countries such as Niger (Nour, Table I).[11][92] Most child marriage involves girls. For instance in Mali the ratio of girls to boys is 72:1, while in countries such as the United States the ratio is 8:1. Marriage may occur as early as birth, with the girl being sent to her husbands home as early as age seven.[11]
^ Jump up to: a b c Aldridge, Robert W.; Story, Alistair; Hwang, Stephen W.; Nordentoft, Merete; Luchenski, Serena A.; Hartwell, Greg; Tweed, Emily J.; Lewer, Dan; Vittal Katikireddi, Srinivasa (2017-11-10). "Morbidity and mortality in homeless individuals, prisoners, sex workers, and individuals with substance use disorders in high-income countries: a systematic review and meta-analysis". Lancet. 391 (10117): 241–250. doi:10.1016/S0140-6736(17)31869-X. ISSN 1474-547X. PMC 5803132. PMID 29137869. All-cause standardised mortality ratios were significantly increased in 91 (99%) of 92 extracted datapoints and were 11·86 (95% CI 10·42–13·30; I2=94·1%) in female individuals