The effect of dexamethasone therapy in prolonged pregnancy

Abstract

Fifty-six patients, chosen by random sampling from a total group of 120 post-term women, received dexamethasone (Decadron, "MSD" 2 mg 3 times a day for 4 days, the other 64 patients acting as controls. The evolution of uterine activity was evaluated using pelvic score (PS) and a modified low dosage oxytocin sensitivyt test (OST) before (T1) and after (T2) the treatment. During the interval from the second to the 6th day inclusive after T1 35 women of the dexamethasone group and 15 of the control group had a spontaneous onset of labour (SO) (0.001 less than P less than 0.01). Five patients in the dexamethasone group with primary rupture of membranes started labour spontaneously within 12 hours after membrane rupture, 7 patients in the control group with primary rupture of membranes received oxytocin as labour did not start within 24 hours. Excluding patients artifically induced, the mean interval from T1 to SO was 6.8 days in the control group and 5.2 days in the dexamethasone group (P less than 0.001). In both groups PS and the sum of Montevideo units (MU) during OST increased from T1 to T2, the increase was significantly greater in the dexamethasone group than in the control group. We found no correlation between the results of OST and the T1--SO interval. Dexamethasone, as used in this study, may promote labour in prolonged human pregnancy. Due to its low potency, it is not a substitute for oxytocin in the induction of labour. The lowered placento-fetal quotient in the dexamethasone group warrants further study of the effects of steroid hormone on placental function.