![]() 2 Because intravenous beta-mimetic drugs can cause severe hypotension and tachycardia, the patient's blood pressure should be monitored frequently. The complications caused by beta-mimetic therapy are listed in Table 5. Oral terbutaline is a more cost-effective alternative. The production of oral ritodrine was discontinued in 1995 because of issues concerning the dose and efficacy of the drug in women in preterm labor. Commonly, terbutaline, in a dosage of 2.5 to 5.0 mg, is given orally 30 minutes before discontinuing the magnesium sulfate infusion, then every two to four hours thereafter to control contractions however, a recent meta-analysis 33 does not support the role of oral therapy after resolution of an acute episode. The infusion is continued until 12 to 24 hours of uterine quiescence is achieved. A continuous infusion of 1 to 4 g per hour is then administrated to maintain a magnesium level between 4 and 6 mEq. A loading dose of 4 to 6 g should be given intravenously over 15 to 30 minutes. The mechanism for preventing uterine contraction is unknown but may be related to calcium antagonist activity. 27, 28 Magnesium sulfate acts centrally to decrease seizures and blocks neuromuscular transmission. ![]() In the future, the greatest value of the test may be to identify a symptomatic patient with a negative test result who may then be followed without drug intervention.Ĭompared with beta-adrenergic agonists, magnesium sulfate is often used as a first-line therapy for tocolysis because it is highly effective and is associated with fewer side effects. 15 The positive predictive value (PPV), that is, the ability to predict that a patient with a positive test result will have a preterm delivery, is as high as 83 percent in symptomatic patients. In symptomatic patients, fetal fibronectin has an excellent sensitivity (69 to 93 percent) 14 – 17 and a negative predictive value as high as 99.7 percent (or, in other words, a one in 333 chance of delivery within one week of a negative test result). Food and Drug Administration labeled fetal fibronectin enzymatic immunoassay for use as a screening test for preterm labor. 5 – 17 The most promising of these markers is the presence of fetal fibronectin in cervicovaginal secretions, which, if positive (defined as greater than 50 ng per mL) after 20 weeks of gestation, indicates decidual disruption. Research into biochemical markers such as fetal fibronectin, possible infectious etiologies such as bacterial vaginosis, and the use of more selective tocolytic therapy offers hope that new therapeutic approaches may increase rates of fetal survival.Ī number of studies have attempted to identify clinical and biochemical markers of pre-term labor and delivery associated with overall poor predictive values ( Tables 2 and 3). The rate of fetal morbidity can be reduced with the early and accurate diagnosis of preterm labor, intervention to delay preterm delivery, administration of corticosteroids and provision of neonatal care. Preconception counseling should emphasize family planning, nutrition, “safe sex techniques,” treatment of sexually transmitted diseases, and avoidance of cigarettes, alcohol, abusive drugs and harmful work conditions. Although the cause of preterm labor is unknown, family physicians who provide obstetric care should familiarize themselves and their patients with the predisposing risk factors. In the United States, preterm delivery affects approximately one in 10 births and is the cause of at least 75 percent of neonatal deaths, excluding those related to congenital malformations. Preterm labor and delivery are among the most challenging obstetric complications encountered by the family physician.
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