Maternal cocaine use and cigarette smoking in pregnancy in relation to amino acid transport and fetal growth.

This review covers the weight of evidence that shows the association of cocaine and cigarette smoking in pregnancy with the impaired transplacental amino acid transport which might give rise to fetal growth restriction (IUGR). Vasoconstrictive effects of both cocaine and nicotine on the placental vasculature are clearly not the only cause for inhibition of placental amino acid uptake and transfer. In vitro studies strongly suggest that cocaine decreases the activity of placental amino acid transport system A and system N, and possibly system l and system y(+), while nicotine decreases the activity of system A. These findings are supported by cordocentesis studies in human IUGR pregnancies not resulting from drug abuse. More work is needed to be done in order to understand the potential additive or synergistic effect of cocaine and cigarette smoking on fetal growth and to determine the underlying cellular mechanisms of interaction with placental amino acid transporters.