The effect of gestational age and labor on placental growth hormone in amniotic fluid

Objective: Placental growth hormone (PGH) is produced by trophoblast. This hormone becomes detectable in maternal serum during the first trimester of pregnancy. Its concentration increases as term approaches and becomes undetectable within one hour of delivery. PGH has important biological properties, including somatogenic (growth promotion), lactogenic, and lipolytic activity. Recently, PGH has been detected in amniotic fluid (AF) of midtrimester pregnancies. The purpose of this study was to determine whether PGH concentrations in AF change with advancing gestational age and in labor at term. Design: AF was assayed for PGH concentrations in samples obtained from patients undergoing genetic amniocentesis between 14 and 18 weeks of gestation (n = 67), normal patients at term not in labor (n = 24), and pregnant women at term in labor (n = 51). PGH concentrations were determined by ELISA. Non-parametric statistics were used for analysis. Results: (1) PGH was detected in all AF samples; (2) patients in the midtrimester had a higher median concentration of PGH in AF than those at term (midtrimester: median: 3140.5 pg/ml; range: 1124.2-13886.5 vs. term: median: 2021.1 pg/ml; range: 181.6-8640.8; p < 0.01); (3) there was no difference in the median concentration of PGH between women at term, not in labor, and those in labor (term not in labor: median: 2113.4 pg/ml; range: 449.3-8640.8 vs. term in labor: median: 2004.1 pg/ml; range: 181.6-8531.5; p = 0.73). Conclusions: (1) PGH is detectable in AF at both mid- and third trimesters; (2) the median AF concentration of PGH is significantly lower at term when compared to the second trimester; (3) labor at term is not associated with changes in the AF concentration of PGH. The role of this unique placental hormone now found in the fetal compartment requires further investigation.