A shift in
progesterone-to-
estradiol balance to
estradiol dominance is assumed to be a prerequisite for regular uterine contractions. To antagonize this effect in
premature labor 24 consecutive women were treated with intravenous
cortisol for 3 days and with weekly
intramuscular injections of
17 alpha-hydroxyprogesterone caproate (17 OHP-C). Twenty-four similar patients treated with
ritodrine served as a reference group. The delivery was postponed by at least 1 week in 21 patients (87.5%) in the
steroid treatment group and in 18 patients (75%) in the
ritodrine group. The
premature labor lasted for 5.1 +/- 0.4 hours (mean +/- SEM) with
steroid therapy and for 2.2 +/- 0.3 hours with
ritodrine. In singleton pregnancies the gestational length and
birth weight of the newborn infants were greater in the
steroid treatment group (N = 23, 39.1 +/- 0.3 weeks, 3,460 +/- 119 gm) than in the
ritodrine group (N = 24, 37.7 +/- 0.4 weeks, 3,106 +/- 118 gm).
Steroid treatment suppressed serum
estradiol concentrations (maximally by 60%) and, to a lesser extent,
testosterone,
estriol, and progresterone levels (maximally by 30%).