Oxytocin in active-phase abnormalities of labor: a randomized study

Article Abstract:

Labor usually proceeds through a latent phase, during which the cervix (''neck'' of the uterus) effaces (shortens, with thinning walls) to an active phase, when dilatation of the cervical opening actually occurs. Two abnormalities of the active phase can occur: primary dysfunctional labor and secondary arrest of cervical dilatation. Oxytocin, a hormone that stimulates uterine contractions, may be administered to correct dysfunctional labor; however, the criteria governing its use vary widely. One viewpoint holds that oxytocin should be administered when an abnormality develops. A second opinion is that the drug should be stared when the rate of cervical dilatation is too slow. To determine which rationale leads to better treatment, a controlled, randomized trial of 759 patients was conducted. The women all were experiencing one of the two abnormalities of active-phase labor. Patients were admitted to the study if the progress of labor became slower than a threshold level and they had a cephalic presentation (fetus positioned in the uterus with its head down). They were assigned to receive either oxytocin or a normal saline (no drug) solution solely on the basis of their hospital case number. Response to treatment was evaluated by measuring the rate of cervical dilatation. Results indicated that the 485 patients with primary dysfunctional labor responded much more after oxytocin than after saline, with a higher percentage of women requiring cesarean delivery after saline (15 percent) than after oxytocin (5 percent). Neonatal outcome, however, did not differ between the groups. Among the women with secondary arrest of cervical dilatation, oxytocin also produced a much greater rate of dilatation. The study was designed to allow women who did not respond to the initial treatment to then receive the other treatment (crossover design). The worst prognosis was faced by those who crossed over, 30 percent of whom required cesarean delivery. Problems with study design are discussed. The results indicate that abnormal labor improves after oxytocin is administered, without an increased incidence of cesarean delivery for fetal distress. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Drug therapy, Oxytocin, Labor, Complicated, Labor complications

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A comparison of Doppler flow velocity waveforms, amniotic fluid columns, and the nonstress test as a means of monitoring post-dates pregnancies

Article Abstract:

Labor is most commonly induced because the pregnancy has progressed beyond 42 weeks (postdatism), but recent research studies indicate that labor induction after 42 weeks does not provide any benefit to the newborn. It is also associated with a significant rise in the rate of cesarean section. In spite of these contraindications to labor induction for postdatism, obstetrical practice has not yet begun more conservative management of prolonged pregnancy. This may be a consequence of a lack of confidence in certain techniques used to assess fetal health after 42 weeks. To evaluate some common techniques for monitoring post-dates pregnancies, a study was carried out of 534 women whose pregnancies exceeded 294 days. The techniques included the nonstress test (NST; recording the fetal heart rate); maternal recordings of fetal movements; ultrasound estimation of the volume of amniotic fluid (in which the fetus floats); and Doppler ultrasound recordings of the blood circulation between the uterus and placenta, and between the placenta and the fetus (uteroplacental and umbilical circulations, respectively). No fetal deaths occurred in the study group; operative delivery was necessary in 52 cases because of fetal distress. None of the tests were good predictors of fetal distress that developed during the second stage of labor. NSTs take as long as 45 minutes to perform and may lead to a high rate of medical intervention (65 percent in this study). Measurement of the volume of amniotic fluid was a better predictor of fetal distress: 60 percent of the patients with decreased amniotic fluid developed this condition in early labor. Doppler studies were most accurate of all the methods for detecting the postmaturity syndrome, a constellation of physical findings that suggest the placenta has become insufficient to support the fetus's needs. The results suggest that Doppler waveform studies from the umbilical artery, combined with ultrasound estimates of the amount of amniotic fluid, provide a reliable indication of fetal health in post-date pregnancies. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Doppler velocimetry in prolonged pregnancy

Article Abstract:

Pregnancies that exceed 42 weeks (294 days) are considered post-term and are associated with an increase in complications and mortality in the period surrounding delivery. Several techniques have been used to evaluate the health of post-term fetuses, one of which is Doppler ultrasonography of maternal and fetal blood vessels. This noninvasive method allows measurement of the blood flow velocity (velocimetry) in the maternal and fetal circulation. In this study, the value of Doppler ultrasonography was assessed in 82 patients with pregnancies of 287 days' or more gestation. The patients underwent several different kinds of tests to evaluate fetal health, including the nonstress test (NST), in which the fetal heart rate is monitored; estimation of the volume of amniotic fluid (in which the fetus floats); and Doppler analysis. Decreased blood flow in the fetal descending thoracic aorta (through which blood is pumped from the heart to the body) was observed in 24 fetuses (called the 'decreased' group); the remaining 58 fetuses had normal Doppler results. The incidence of oligohydramnios (low amniotic fluid volume); meconium (fetal feces)-stained amniotic fluid (indicative of fetal distress and cause of lung problems); abnormal NST results; and cesarean delivery was higher in the decreased than the normal group. The study indicates that Doppler flow measurements of the fetal descending aorta may be helpful in identifying high-risk fetuses in prolonged pregnancies. (Consumer Summary produced by Reliance Medical Information, Inc.)

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