Effect of maternal age and growth on placental nutrient transport: potential mechanisms for teenagers ’ predisposition to small-for-gestational-age birth?

nutrient transport: potential mechanisms for teenagers ’ predispo-sition to small-for-gestational-age birth? Am J Physiol Endocrinol Metab 302: E233–E242, 2012. First published October 25, 2011; doi:10.1152/ajpendo.00192.2011.—Teenagers have an increased risk of delivering small-for-gestational-age (SGA) infants. Young maternal age and continued skeletal growth have been implicated as causal factors. In growing adolescent sheep, impaired placental de-velopment and nutrient transfer cause reduced birth weight. In human pregnancies, SGA is associated with reduced placental amino acid transport. Maternal growth has no effect on placental morphology or cell turnover, but growing teenagers have higher birth weight: placental weight ratios than nongrowing teenagers. We hypothesized that placental nutrient transporter activity would be affected by ma-ternal age and/or growth status. Placentas from teenagers and adults were collected. Teenagers were defined as growing or nongrowin