James A. Thorp

The effect of intrapartum epidural analgesia on nulliparous labor: A randomized, controlled, prospective trial

OBJECTIVE Our purpose was to determine the effect of epidural analgesia on nulliparous labor and delivery. STUDY DESIGN Normal term nulliparous women in early spontaneous labor were randomized to receive either narcotic or epidural analgesia. RESULTS When compared with the group receiving narcotic analgesia (n = 45), the group receiving epidural analgesia (n = 48) had a significant prolongation in the first and second stages of labor, an increased requirement for oxytocin augmentation, and a significant slowing in the rate of cervical dilatation. Epidural analgesia was associated with a significant increase in malposition (4.4% vs 18.8%, p < 0.05). Cesarean delivery occurred more frequently in the epidural group (2.2% vs 25%, p < 0.05), primarily related to an increase in cesarean section for dystocia (2.2% vs 16.7%, p < 0.05). CONCLUSIONS In a randomized, controlled, prospective trial epidural analgesia resulted in a significant prolongation in the first and second stages of labor and a significant increase in the frequency of cesarean delivery, primarily related to dystocia.

The effect of continuous epidural analgesia on cesarean section for dystocia in nulliparous women

Epidural analgesia in labor is generally accepted as safe and effective and therefore has become increasingly popular. However, little is known regarding the effect of epidural analgesia on the incidence of cesarean section for dystocia in nulliparous women. During the first 6 months of 1987 we studied 711 consecutive nulliparous women at term, with cephalic fetal presentations and spontaneous onset of labor. Comparison of 447 patients who received epidural analgesia in labor with 264 patients who received either narcotics or no analgesia was performed. The incidence of cesarean section for dystocia was significantly greater (p less than 0.005) in the epidural group (10.3%) than in the nonepidural group (3.8%). There remained a significantly increased incidence (p less than 0.005) of cesarean section for dystocia in the epidural group after selection bias was corrected and the following confounding variables were controlled by multivariate analysis: maternal age, race, gestational age, cervical dilatation on admission, use of oxytocin, duration of oxytocin use, maximum infusion rate of oxytocin, duration of labor, presence of meconium, and birth weight. The incidence of cesarean section for fetal distress was similar (p greater than 0.20) in both groups. There were no clinically significant differences in frequency of low Apgar scores at 5 minutes or cord arterial and venous blood gas parameters between the two groups. This study suggests that epidural analgesia in labor may increase the incidence of cesarean section for dystocia in nulliparous women.

The cesarean birth epidemic: Trends, causes, and solutions

Abstract We should anticipate a continued slow fall in cesarean birth rates over time as initiatives for health care improvement help us focus on strategies to avoid interference in the normal process of labor and vaginal birth. (Am J Obstet Gynecol 1996;175:369-74.)

Routine umbilical cord blood gas determinations

Between 1986 and 1988, 1924 term nulliparous patients with spontaneous onset of labor were studied to assess the importance of obtaining umbilical cord blood gas levels on all deliveries. The umbilical cord arterial and venous pH values (expressed as mean +/- 2 SD) were 7.24 +/- 0.14 (n = 1694) and 7.32 +/- 0.12 (n = 1820), respectively. The incidence of newborn depression (1- or 5-minute Apgar score less than 7) was 14.1%; of these depressed newborns, the incidence of normal umbilical cord arterial pH values (greater than or equal to -2 SD) was 77.8%. Of the vigorous newborns, there was a 2.1% incidence of umbilical cord arterial blood acidemia. Umbilical cord arterial blood acidemia in vigorous newborns was not highly predictive of specific morbidity in the immediate newborn period. Regression analysis demonstrated the umbilical cord arterial pH to correlate best with the Apgar scores when compared with all other arterial or venous blood gas measurements. We reached the following conclusions: (1) that obtaining cord arterial pH values in vigorous newborns should be considered since the values will provide objective documentation or normal fetal acid base balance in 98% of infants. (2) Only a cord arterial pH determination is recommended since it reflects fetal or newborn status more accurately than all other measurements. Additional measurements increase the likelihood of abnormal results and do not contribute to neonatal management. (3) An umbilical cord blood pH value is extremely useful in ruling out the diagnosis of birth asphyxia in the depressed newborn.

Low-dose aspirin inhibits thromboxane, but not prostacyclin, production by human placental arteries

Preeclampsia is associated with increased thromboxane and decreased prostacyclin production by the placenta. Low-dose aspirin can selectively inhibit thromboxane production in the adult circulation, but its effects on placental vascular production of thromboxane and prostacyclin are incompletely understood. We therefore studied the effects of low-dose aspirin on the production rates of prostacyclin and thromboxane, with and without vasoconstricting doses of angiotensin II, in human placental arteries. Chorionic plate arteries were incubated and samples were assayed for thromboxane and prostacyclin by radioimmunoassay of their stable metabolites. Production rates for prostacyclin were similar in the control, aspirin, angiotensin II, and angiotensin II plus aspirin groups. Mean (+/- SEM; n = 8) thromboxane production rates in the aspirin (1.4 +/- 0.5 pg/mg/hr) and angiotensin II plus aspirin (2.9 +/- 0.6 pg/mg/hr) groups were significantly lower (p less than 0.05) than values in the control (8.6 +/- 2.7 pg/mg/hr) and angiotensin II (6.7 +/- 1.3 pg/mg/hr) groups. We conclude that low-dose aspirin significantly decreases production of thromboxane in placental arteries both with and without vasoconstricting doses of angiotensin II.

The effect of maternal oxygen administration during the second stage of labor on umbilical cord blood gas values: A randomized controlled prospective trial

OBJECTIVE Our aim was to determine whether supplemental oxygen during the second stage of normal labor affects cord blood gas and cooximetry values. STUDY DESIGN Patients at term pregnancy were prospectively randomized to the control or treatment group at the onset of the second stage of labor. The treatment group received 10 L/min oxygen by face mask, which result in a mean fractional inspired oxygen concentration of 0.81. RESULTS There were 86 patients randomized into the study. In the oxygen group there were significantly more cord arterial pH values < 7.20 (9/41 vs 2/44, p < 0.05). The control group was compared with two subgroups of patients receiving oxygen: those receiving oxygen therapy for < or = 10 minutes and those receiving oxygen for > 10 minutes. Analysis of variance demonstrated significant differences (7.285 +/- 0.058, 7.312 +/- 0.056, 7.237 +/- 0.064; F test 8.3, p = 0.0005). Among several independent variables, regression analysis demonstrated that only duration of oxygen therapy had a significant inverse relation to cord arterial pH (F test = 15.6, p = 0.0002). CONCLUSIONS Prolonged oxygen treatment during the second stage of normal labor resulted in a deterioration of cord blood gas values at birth.

The risk of pulmonary edema and colloid osmotic pressure changes during magnesium sulfate infusion

OBJECTIVES The purposes of this study were to evaluate the effect of magnesium sulfate therapy on colloid osmotic pressure and to determine whether changes in colloid osmotic pressure increased the risk of pulmonary edema. STUDY DESIGN During a 1-year time period 294 patients received parenteral magnesium sulfate for the treatment of preterm labor or preeclampsia. Both changes in colloid osmotic pressure and magnesium sulfate values and their relationship to clinical outcome parameters were analyzed. RESULTS Serum magnesium levels were similar for both patients with preeclampsia and patients with preterm labor. Pulmonary edema developed in only four patients, all of whom had preeclampsia and low colloid osmotic pressure values. CONCLUSIONS This study demonstrated that parenteral magnesium sulfate therapy does not cause significant changes in colloid osmotic pressure values until nearly 48 hours of continuous therapy.

Effect of antenatal and postnatal corticosteroid therapy on weight gain and head circumference growth in the nursery.

OBJECTIVE To assess the effect of antenatal and postnatal corticosteroids on head circumference growth and weight gain from birth to discharge. METHODS We conducted a retrospective analysis of non‐anomalous newborns admitted to the neonatal intensive care unit from 23 to 34 6/7 weeks of gestation. Independent variables included maternal age, race, nulliparity, poor prenatal care, multiple gestation, obstetric complications, alcohol, tocolytic drugs, smoking, illicit drugs, gestational age at birth, presentation, method of delivery, 5‐minute Apgar score < 7, surfactant use, severe intracranial hemorrhage, and length of stay. RESULTS Antenatal and postnatal corticosteroids were given in 62% and 14% of the newborns, respectively, and 10% of newborns received both. The mean (±SD) weight gain and head circumference growth in the nursery was 440 ± 582 g (n = 14,217) and 2.54 ± 3.42 cm (n = 12,808), respectively. After multivariable analysis, use of antenatal corticosteroids did not affect weight gain (3.6 ± 4.6 g) and head circumference growth (0.05 ± 0.04 cm) compared with no exposure to perinatal corticosteroids, but postnatal corticosteroids were associated with significant reductions in weight gain and head circumference growth (−120 ± 12.2 g and −0.53 ± 0.11 cm, respectively). CONCLUSIONS Antenatal corticosteroid therapy did not affect weight gain or head circumference growth in the nursery, even when used in conjunction with postnatal corticosteroid therapy.

Comparison of the vasoactive effects of leukotrienes with thromboxane mimic in the perfused human placenta

Vasoactive effects of leukotrienes and thromboxane mimic were tested in the perfused human placental cotyledon. Tissue viability was demonstrated by oxygen consumption and by carbon dioxide and lactate production. Vasoconstrictive effects of leukotrienes B4, C4, and D4 were compared with those of a known potent vasoconstrictor, thromboxane mimic (U 46619). The leukotrienes and thromboxane mimic were administered as bolus injections into a chorionic plate artery in doses ranging from 10(-6) to 25 micrograms. In each placenta only one leukotriene was compared with thromboxane mimic. Vasoconstrictive effects were determined by maximum increases in resistance occurring after each injection. Thromboxane mimic caused significantly greater increases in resistance than any of the leukotrienes (p less than 0.001). Thromboxane mimic and leukotriene D4 had significantly lower threshold doses than leukotriene B4 or C4 (p less than 0.001). We concluded: (1) Thromboxane mimic is a potent vasoconstrictor in the human placental vasculature; (2) leukotrienes also cause vasoconstriction but are much less potent than thromboxane; (3) thromboxane mimic and leukotriene D4 have vasoconstrictor effects at significantly lower (p less than 0.001) concentrations than leukotriene B4 or C4.

Maternal death after second-trimester genetic amniocentesis.

BACKGROUND: We report a maternal death after a second-trimester amniocentesis. CASE: An uncomplicated amniocentesis was performed using sterile technique and ultrasound guidance. A refrigerated amniotic fluid specimen demonstrated negative leukocyte esterase activity, negative Gram stain for bacteria and white blood cells, and normal glucose and interleukin-6. The patient died from Escherichia coli sepsis and disseminated intravascular coagulation 40 hours after the amniocentesis. The autopsy showed normal- appearing needle entries into the skin and uterus without evidence of bowel adhesion or a needle track through the bowel. CONCLUSION: Genetic counselors and obstetric care providers should be aware of potential serious maternal morbidity and mortality that may occur subsequent to uncomplicated amniocentesis.