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

Abstract

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 development 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 maternal age and/or growth status. Placentas from teenagers and adults were collected. Teenagers were defined as growing or nongrowing based on knee height measurements. System A amino acid transporter activity was quantified as sodium-dependent uptake of [(14)C]methylaminoisobutyric acid into placental fragments. Teenagers had lower placental system A activity than adults (P < 0.05). In adults, placental system A activity was lower in SGA infants than appropriate-for-gestational-age (AGA) infants (P < 0.05). In teenagers, AGA and SGA infants had lower placental system A activity than AGA infants born to adults (P < 0.05). Placental system A activity was higher in growing teenagers than in nongrowing teenagers (P < 0.001). Placental mRNA expression of system A transporter isoforms SLC38A1 and -2 was lower in teenagers than in adults (P < 0.05) but did not differ between growing and nongrowing teenagers. There was no difference in transporter protein expression/localization between cohorts. Teenagers have inherently reduced placental transport, which may underlie their susceptibility to delivering SGA infants. Growing teenagers appear to overcome this susceptibility by stimulating the activity, but not expression, of system A transporters.

The impact of uterine immaturity on obstetrical syndromes during adolescence

“…However, the activity of system A transporters was higher in placentas from growing compared with nongrowing teenagers. 77 These observations are broadly in line with an earlier study demonstrating that the villous/capillary surface area in placentas from adolescent mothers does not correlate with either maternal chronological age or bone age. However, this study did find an inverse correlation between the placental villous/capillary surface and gynecological age, further suggesting that uterine immaturity is the primary driver of placental dysfunction during adolescence.…”

Maternal Diet and Nutrient Requirements in Pregnancy and Breastfeeding. An Italian Consensus Document

“…To date, there is limited data on the precise nutritional needs of adolescents during pregnancy and lactation, but the increased risk of preterm delivery and low birth weight has been correlated to alterations of placental function in pregnant adolescents [90,91]. It has been shown that, in addition to biological immaturity, the inadequate nutritional status (e.g., breakfast skipping, improper weight loss diet, energy-dense foods) could play important roles in the onset of complications in the perinatal period [92].…”

Placental dysfunction is associated with altered microRNA expression in pregnant women with low folate status

“…A nested case–control study was utilized for placental analyses, with low and adequate folate status cohorts selected to match most closely on demographic and biophysical characteristics. Sample sizes were dictated by power calculations based on previous studies .…”

“…Sodium‐dependent uptake of 14 C‐methylaminoisobutyric acid (PerkinElmer, Buckinghamshire, UK) was measured to assess amino acid transporter system A activity in placental fragments as described . The rate of uptake over 10–30 min was calculated and normalized for fragment protein content.…”