It has been introduced and analyzed a mathematical model based on integral equations, which turns into a dynamical system of non-linear differential equations to account for the risk of microcephaly incidence caused by the Zika virus. A specific pregnant women susceptible group has been accounted for. The epidemic threshold (basic reproduction number) has been obtained by implementing the next generation matrix method. A sensitivity analysis with respect to each parameter has been applied to that threshold. Finally, the incidence to the exposure is obtained by performing several system simulations.