Addition of magnesium sulfate improves effectiveness of ritodrine in preventing premature delivery

From October, 1981, to July, 1983, 225 patients were evaluated for premature labor at Forsyth Memorial Hospital. Sixty-five of these patients were considered to be candidates for intravenous ritodrine treatment. Of this group, 24 patients were successfully treated and had pregnancy prolongation ranging from 1 to 17 weeks. Forty-one patients did not respond to maximal intravenous ritodrine therapy (300 to 350 micrograms/min). Eleven patients subsequently delivered within 24 to 48 hours of treatment initiation. The remaining 30 patients received intravenous magnesium sulfate (1 to 3 gm/hr) in addition to intravenous ritodrine. Eighteen patients responded favorably to this combination treatment and had pregnancy prolongation ranging from 1 to 11 weeks. Twelve patients delivered within 1 week from treatment initiation. In all cases where pregnancy prolongation was achieved, birth weight and neonatal outcome were significantly improved compared to patients who did not respond to either intravenous ritodrine alone or intravenous ritodrine and magnesium sulfate combination. Treatment related maternal/fetal complications were not significantly different in the various groups examined. From the foregoing we conclude that, in a select group of patients in premature labor not responding to conventional ritodrine therapy, magnesium supplementation in pharmacologic doses could have a beneficial effect with respect to pregnancy outcome.