To compare the tocolytic efficacy and side effects of parenteral and oral magnesium and terbutaline.
Methods
Ninety-eight patients in labor between 23-35 weeks were prospectively entered into a controlled trial of intravenous and oral magnesium versus subcutaneous and oral terbutaline. Tocolytic effectiveness was judged by delay of delivery for 48 hours or 1 week, and to 37 weeks or more. The need to change therapy to the alternate drug was identified, as were side effects. Entrance characteristics of the population, initial pelvic examination, and concomitant infection or cervicovaginal isolates were noted. Outcomes included gestational age at delivery, birth weights, and Apgar scores. Outcome analysis was based on initial tocolytic therapy.
Results
Significantly more patients in the magnesium group delivered at 37 weeks or more: 34 of 46 versus 27 of 52 (P < .05). No significant differences were found for delivery by 48 hours or 1 week. The interval between treatment and delivery was greater for magnesium: 7.1 +/- 3.9 versus 5.0 +/- 3.2 weeks (P < .005). Failure to achieve 37 completed weeks was more often due to obstetric complications than to preterm labor itself. Tocolytic effectiveness was reduced if secondary therapy or re-treatment was required or if the patient had cervical dilatation of 3 cm or greater. Infectious complications were common but were not associated with tocolytic effectiveness. Side effects were more noticeable with oral magnesium and subcutaneous terbutaline.
Conclusions
For short-term tocolysis, no significant difference was found between magnesium and terbutaline. Magnesium was associated with a higher term delivery rate. Idiopathic preterm labor accounted for only a small part of the overall prematurity in the study population.
Chau, A. C., Gabert, H. A., & Miller, J. M. (1992). A prospective comparison of terbutaline and magnesium for tocolysis. Obstetrics and gynecology, 80(5), 847-851.
Chau AC, Gabert HA, Miller JM. A prospective comparison of terbutaline and magnesium for tocolysis. Obstet Gynecol. 1992;80(5):847-851.
Chau, Ann C., et al. "A prospective comparison of terbutaline and magnesium for tocolysis." Obstetrics and gynecology, vol. 80, no. 5, 1992, pp. 847-851.
We compared nifedipine and ritodrine for treatment of preterm labor with respect to neonatal outcome. We conducted an open randomized multicenter study of neonatal outcome in 185 women who received either oral nifedipine (n = 95) or intravenous (IV) ritodrine (n = 90) for treatment of preterm labor. Secondary outcome measures included neonatal mortality and morbidity, especially neonatal intensive care unit (NICU) admission, respiratory distress syndrome (RDS), and intracranial bleeding. There were no significant differences in umbilical artery pH values and Apgar scores between groups. Nifedipine was associated with lower admission rates to the NICU (49% versus 66%; odds ratio 0. 51, confidence interval 0.28, 0.93) compared with ritodrine, and lower incidences of RDS (21% versus 37%; 0.46, 0.24, 0.89), intracranial bleeding (18% versus 31%; 0.48, 0.24, 0.96), and neonatal jaundice (52% versus 67%; 0.53, 0.29, 0.97). Logistic regression analysis showed that even after correction for gestational age at birth, newborn risk of RDS, intracranial bleeding, or neonatal jaundice was significantly lower in the nifedipine group than the ritodrine group. Nifedipine for treatment of preterm labor was associated with a lower incidence of neonatal morbidity than ritodrine. That difference appeared to be partly because of the higher tocolytic efficacy of nifedipine and partly because of an intrinsic beneficial effect of nifedipine, or the lack of harmful effects when compared with ritodrine.
The medical records of 330 patients treated with terbutaline infusion for the inhibition of preterm labor were reviewed over a five-year period. In patients with intact membranes the results were uniformly good, particularly when treatment was instituted before the 30th week. Half these patients had a prolonged labor of six weeks or more; in most cases of treatment failure complications already existed on admission. In only nine patients (2.7%) terbutaline treatment was predominantly maternal tachycardia or vomiting. Two patients had chest symptoms, but in no case was pulmonary edema diagnosed. The results suggested that a low incidence of severe side effects can be obtained if the following glucose is used as the infusion medium, instead of sodium chloride; concentrated solutions are given to avoid fluid overload; the patients are carefully controlled; and the infusion is immediately reduced or stopped if signs of severe side effects appear.
Progesterone support in pregnancy has been in use for over 60 years, having received its start in the 1940s. Its initial use was in patients who had habitual spontaneous abortion caused by luteal phase deficiency. More recently, the administration of progesterone later in pregnancy has been considered to be justified because of an observed decrease in circulating progesterone with the onset of labor, an association of premature labor with decreased progesterone concentrations, and the observation that progesterone has a tocolytic effect. A considerable boost to the use of progestational agents to reduce preterm delivery was received with the publication of two papers which showed a significant reduction in preterm delivery rates with the prophylactic administration of either progesterone or 17-a hydroxyprogesterone caproate. Recently it has been shown, however, that its use is not universal. This may be related to the significant late sequelae that were documented following the in utero exposure of the fetus to the potent steroid diethylstilbestrol (DES) and that this bad experience cast “a long shadow,” In spite of this, the use of progesterone, at least in early pregnancy, is widespread in the various artificial reproductive programs and is growing in its use as an agent to reduce prematurity. Over the years, there has been an extraordinary amount of confusion related to the use of progesterone support in pregnancy. The Food & Drug Administration (FDA) created some of this confusion. In various labeling of progesterone products by the FDA, one of the contraindications to the use of oral progesterone is listed as “known or suspected pregnancy.” And, yet, no such contraindication is identified for the use of progesterone gel. In fact, progesterone gel is indicated for progesterone supplementation or replacement as a part of an assisted reproductive technology (ART) treatment program for infertile women with a progesterone deficiency. To make this even more confusing, oral progesterone, while it was contraindicated in “known or suspected pregnancy,” its official labeling stated that it “should be used during pregnancy only if indicated (see contraindications).” Also, up until very recently, there was a dire “warning” contained in the labeling for USP progesterone injection in sesame seed oil regarding an increased possibility of birth defects. An analysis of the fetal safety of isomolecular progesterone (Pregn-4-ene-3,20-dione) administration during the course of 1,310 pregnancies over a 35-year period of time (1979-2014) was undertaken to address this confusion.
Preterm birth complicates 8-10% of all pregnancies in the United States and is the leading cause of infant morbidity and mortality. Neonatal morbidity and mortality is concentrated among very low-birthweight and extremely premature infants, particularly those delivered prior to 30 weeks' gestational age. In addition to the contribution of preterm birth to neonatal morbidity and mortality, the economic costs associated with this pregnancy complication are staggering. Efforts to reduce the preterm birth rate have been largely focused on prevention and early intervention with treatment for preterm labor. Mixed results regarding the success of prematurity prevention programs have been reported, and controversy continues to surround the efficacy of tocolytic therapy in the treatment of preterm labor. Although neonatal survival for infants born at early gestational ages has steadily improved in recent years, survival of infants delivered prior to 24 weeks' gestation remains very poor. Additionally, despite this decline in neonatal mortality, the United States still lags behind most industrialized nations in infant mortality, and no change in the rate of low birthweight has occurred in recent decades. Multiple lines of evidence support a role for infection as an etiologic factor in preterm labor. Although this association has been well known for many years, a wealth of new data is emerging, linking subclinical genital tract infection with spontaneous preterm birth, particularly among pregnancies that result in birth prior to 30 weeks' gestational age as a result of spontaneous preterm labor or preterm, premature rupture of membranes. Conversely, preterm birth that occurs closer to term is less likely to be associated with genital tract infection. Improved understanding of the link between genital tract infection and preterm birth now provides an exciting potential for the development of sensitive new markers to identify women at risk and effective interventions to prevent preterm birth. A review and comment on this growing literature is provided.