Concentrations of Serum Total Activin A and Inhibin A in Preterm and Term Labor Patients: A Cross-Sectional Study

OBJECTIVE: To compare maternal serum levels of total activin A and inhibin A in preterm and term patients who are in labor or not in labor. METHODS: A cross-sectional study compared activin A and inhibin A in thefollowinggroups ofpatients: preterm and in labor (n = 65), preterm and not in labor (n = 96), term and in labor (n = 65), and term and not in labor (n = 65). Preterm was defined as 23-34 weeks ' gestation and term as 37-42 weeks' gestation. Labor was defined as regular contractions with progressive cervical change or an initial examination revealing cervical dilation of 1-3 cm with 50 % effacement or more. Follistatin levels were analyzed in a subset of 12 patientsfrom each group. Analytes were measured by two-site enzyme-linked immunosorbent assays. RESULTS: Activin A levels were higher in the preterm laborgroup (median 1.38 multiples ofthe median [MoM], interquartile range [IQR 1.01 MoM) compared with the preterm nonlabor group (median 1.0 MoM, IQR 0. 78 MoM, P <.05) and in the term labor group (median 1.37 MoM, IQR 1. 74 MoM) compared with the term nonlaborgroup (median 1. 0 MoM, IQR 0. 87 MoM, P <.05). Inhibin A levels were higher in the preterm labor group (median 1.27 MoM, IQR 0. 73 MoM) compared with the preterm nonlabor group (median 1.0 MoM, IQR 0.58 MoM, P <.05). Post-hoc analysis of activin A and inhibin A elevations in the preterm labor group revealed a significant effect only during 31-34 weeks' gestation. The total activin Afollistatin ratio, an indirect measure offree activin A, was similar between labor and nonlabor gestational age-matched patient groups. CONCLUSIONS: Levels oftotal activin A and inhibin A were increased in patients during labor; however, based on the moderate degree and narrow gestational age range of the increased levels, these analytes are not likely to be clinically useful in predicting preterm labor. (j Soc Gynecol Investig 2003;10:231-6