Parathyroid hormone levels in preterm and term labor.

This prospective study was undertaken to test the hypothesis that parathyroid hormone (PTH) might be involved in preterm or term labor. Four groups of patients were formed, 15 patients in each group. The preterm labor group were patients who were admitted to our perinatal care unit with preterm labor and unruptured membranes (< 35 weeks' gestation). The preterm or term nonlabor control groups were patients matched for gestational age, maternal age, and parity, who were not in labor. The term labor group were patients matched for maternal age and parity who were in active labor. Mean (+/-SD) level of biologically intact PTH was 18.9 +/- 10.6 pgr/mL, 7.6 +/- 4.7 pgr/mL, 20.8 +/- 10.1 pgr/mL, 13.7 +/- 5.3 pgr/mL in preterm labor group, preterm nonlabor group, term labor group, and term nonlabor group, respectively (p < 0.05). No statistically significant differences were observed in the levels of calcium, phosphorus, magnesium, or albumin. We therefore suggest that PTH may have a role in preterm or term labor. The nature of its role should be investigated in further studies.