Are pregnant teenagers still in rapid growth?

Longitudinal analysis of 1,601 teenage girls, followed up through two or three pregnancies, provided no evidence that the larger pregnancy weight gains observed in younger teenage mothers were attributable to rapid growth. These data were consistent with the time elapsed between menarche and the first pregnancy and refuted popular explanations for the higher pregnancy weight gains in early teenage pregnancy. Fluid retention and increased fluid volume, rather than additions to maternal body mass, were more likely explanations for the high weight gain of younger teenage mothers.