A. P. P. Moraes, S. M. Barreto, V. M. A. Passos, P. S. Golino, J. A. Costa, and M. X. Vasconcelos, “Incidence and main causes of severe maternal morbidity in São Luís, Maranhão, Brazil: a longitudinal study”, Sao Paulo Med J, vol. 129, no. 3, pp. 146–152, May 2011.