Young Maternal Age, Body Composition and Gestational Intake Impact Pregnancy Outcome: Translational Perspectives

Abstract

Birth weight is a robust predictor of health and well-being immediately after delivery and throughout the life course. Maternal body composition at conception and gestational intake thereafter impacts prenatal growth velocity and birth weight irrespective of maternal age, but the most pronounced risk of poor outcome is when pregnancy coincides with adolescence and continued or incomplete growth of the mother. Experimental ovine paradigms have helped define the impact of nutrition in mediating pregnancy outcome in young adolescents. Low maternal nutrient status at conception has a modestly negative influence on placental growth and birth weight, but it is gestational intake after conception, particularly during the first third of pregnancy, which has the most profound influence on fetal development. Relative to optimally nourished controls, age-matched adolescents overnourished throughout pregnancy exhibit rapid maternal growth and increasing adiposity at the expense of the conceptus. Placental growth and vascular development, uteroplacental blood flows and fetal nutrient supply are compromised, and premature delivery of low birthweight lambs with a 45\% incidence of marked intrauterine growth restriction (IUGR) ensues. A more modest effect on fetal growth is evident in undernourished mothers (17\% incidence of IUGR). Here preventing maternal growth gradually depletes maternal body reserves and directly lowers nutrient availability in the maternal circulation independent of any change in placental size or gestation length. The maternal and placental adaptations to these diverse gestational intakes and the consequences for the fetus are presented together with the translational implications for detecting and avoiding birthweight extremes in human pregnancy.