Further Evidence that an Episode of Premature Labor Is a Pathologic State: Involvement of the Insulin-Like Growth Factor System

Abstract

<b><i>Introduction:</i></b> Approximately 47% of women with an episode of preterm labor deliver at term; however, their infants are at greater risk of being small for gestational age and for neurodevelopmental disorders. In these cases, a pathologic insult may disrupt the homeostatic responses sustaining pregnancy. We tested the hypothesis of an involvement of components of the insulin-like growth factor (IGF) system. <b><i>Methods:</i></b> This is a cross-sectional study in which maternal plasma concentrations of pregnancy-associated plasma protease (PAPP)-A, PAPP-A2, insulin-like growth factor-binding protein 1 (IGFBP-1), and IGFBP-4 were determined in the following groups of women: (1) no episodes of preterm labor, term delivery (controls, <i>n</i> = 100); (2) episode of preterm labor, term delivery (<i>n</i> = 50); (3) episode of preterm labor, preterm delivery (<i>n</i> = 100); (4) pregnant women at term not in labor (<i>n</i> = 61); and (5) pregnant women at term in labor (<i>n</i> = 61). Pairwise differences in maternal plasma concentrations of PAPP-A, PAPP-A2, IGFBP-1, and IGFBP-4 among study groups were assessed by fitting linear models on log-transformed data and included adjustment for relevant covariates. Significance of the group coefficient in the linear models was assessed via t-scores, with <i>p</i> &lt; 0.05 deemed a significant result. <b><i>Results:</i></b> Compared to controls, (1) women with an episode of premature labor, regardless of a preterm or a term delivery, had higher mean plasma concentrations of PAPP-A2 and IGFBP-1 (each <i>p</i> &lt; 0.05); (2) women with an episode of premature labor who delivered at term also had a higher mean concentration of PAPP-A (<i>p</i> &lt; 0.05); and (3) acute histologic chorioamnionitis and spontaneous labor at term were not associated with significant changes in these analytes. <b><i>Conclusion:</i></b> An episode of preterm labor involves the IGF system, supporting the view that the premature activation of parturition is a pathologic state, even in those women who delivered at term.