Leptin and maternal growth during adolescent pregnancy

Background: Maternal growth on the basis of knee height occurs in nearly 50% of pregnant teenagers and is associated with greater gestational weight gain and accrual of subcutaneous fat in the mother but lower fetal growth compared with nongrowing teenagers and mature pregnant women. Objective: The objective of this study was to determine whether leptin is a biomarker for continued maternal growth. Design: Leptin concentrations were measured in 162 growing and nongrowing teenage gravidas (aged ≤ 18 y) and in mature gravidas (aged 19-29 y) from the Camden Study at 2 time points during pregnancy and 1 time point postpartum. Results: Growing teenagers had leptin concentrations that increased with gestation and were higher at 28 wk gestation and postpartum than in nongrowing teenagers and mature gravidas. The differences were related to a leptin surge between entry into the study (16.9 wk) and week 28, primarily in still-growing gravidas. Leptin-surge quartiles were associated with higher knee-height velocity and weight gain, increased skinfold thicknesses in late pregnancy (28 wk) and early postpartum (4-6 wk), and changes in postpartum weight and body mass index. For the highest quartile, low birth weight increased >5-fold, fetal growth restriction increased >6-fold, and infant birth weight decreased by ≃200 g. Gravidas who developed pregnancy-induced hypertension showed a different pattern - higher leptin concentrations at entry and week 28, no difference in the leptin surge, and no postpartum difference in leptin concentration. Conclusion: A leptin surge by week 28 appears to mark reduced mobilization of maternal fat stores that is associated with maternal growth on the basis of knee height during adolescent pregnancy.