Reduced fetal exposure to aspirin using a novel controlled-release preparation in normotensive and hypertensive pregnancies.

OBJECTIVES: To examine the fetal effects of a novel controlled-release, low dose aspirin preparation in normal and hypertensive pregnancies. DESIGN: Random double-blind study. Participants assigned to receive conventional formulation aspirin (75 mg), controlled-release low dose aspirin (75 mg), or a matching placebo. SETTING: National Maternity Hospital, Dublin. PARTICIPANTS: Eighteen women with an uncomplicated pregnancy and 18 women with preeclampsia. MAIN OUTCOME MEASURES: Urine was analysed for metabolites of thromboxane and prostacyclin by gas chromatography, mass spectrometry. Serum thromboxane B2 was determined in maternal and cord blood. RESULTS: Both aspirin preparations reduced maternal serum thromboxane B2 by 95% and induced similar reductions in the urinary 11-dehydro-thromboxane B2, a major metabolite of thromboxane A2 in vivo. In contrast, neither preparation altered urinary 2,3-dinor-6-keto PGF1alpha, the major metabolite of prostacyclin. Despite their similar effects in the mothers, the two aspirin preparations differed in their effects on the fetus. While both suppressed cord fetal thromboxane B2, this was significantly (P < 0.005) less for the controlled-release preparation (210+/-42 ng/ml for placebo vs 109+/-22 ng/ml for controlled-release aspirin and 44+/-9 ng/ml for regular oral aspirin). CONCLUSIONS: At equivalent maternal suppression of serum thromboxane B2, a controlled aspirin release preparation results in lower fetal exposure than regular oral aspirin.

Hyponatraemia and non-electrolyte solutions in labouring primigravida.

We performed a prospective randomised study on one hundred primigravid women who required oxytocin to augment labour, comparing dextrose infusion with normal saline. After delivery, the 45 patients whose oxytocin was infused in dextrose had significantly lower serum sodium levels in both mother and baby compared to the 48 patients who had their oxytocin administered in normal saline. This was particularly evident in those cases where epidural analgesia was employed.

Does oxytocin augmentation increase perinatal risk in primigravid labor?

To assess the influence of high-dose oxytocin augmentation of spontaneous labor, a consecutive series of 30,874 primigravid term deliveries were analyzed for adverse perinatal outcome. In spite of a longer mean duration of labor, the frequencies of asphyxial perinatal death, neonatal seizures, and abnormal neonatal neurologic behavior were not significantly increased in 14,119 (45%) oxytocin-treated patients. There was no case of uterine rupture in any primigravid labor during the study. These results from 13 years of clinical practice provide reassurance about maternal and fetal safety if oxytocin is used as part of a protocol of active management to correct dystocia when spontaneous primigravid labor with vertex presentation fails to progress.

Fetal acidosis in labour: a prospective study on the effect of parity.

The effect of parity on intrapartum fetal scalp pH was investigated in 6466 patients in labour with a live fetus who were delivered in 1987. 350 (5.4%) required fetal scalp blood sampling for pH (FBS), 236 primigravidae (10.4%) and 114 multigravidae (2.7%) (P less than 0.001). Fetal acidosis (pH less than 7.20) was detected in 35 patients, 27 primigravidae (11.4%) and 8 multigravidae (7.0%) (P less than 0.001). The incidence of intrapartum acidosis in the 2275 primigravidae and the 4191 multigravidae was 1.2 and 0.2% respectively (P less than 0.001). The two deaths from birth asphyxia and three cases of neonatal seizures occurred in primigravidae. In primigravidae requiring FBS, fetal acidosis was not associated with the use of oxytocin or with increased duration of labour. Neonatal seizures were more common overall in primigravidae than in multigravidae and more common in patients requiring FBS than in those not requiring FBS (P less than 0.05). The higher incidence of FBS, fetal scalp acidosis and neonatal seizures in primigravidae has important implications for intrapartum fetal monitoring.

Effect of active management on latent phase labor.

The effect of active management on latent phase labor was assessed in 197 consecutive nulliparous women. Active management resulted in a significant shortening of the latent phase but had no effect on active phase labor. Patients undergoing induction of labor had latent phases that were almost identical to the accepted norm. The effect of active management may be due to early diagnosis of labor and early intervention in the form of artificial rupture of membranes and selective high-dose oxytocin infusion.

The influence of birth weight on labor in nulliparas.

The purpose of this study was to examine the hypothesis that dystocia in nulliparas is directly related to birth weight. The study was confined to the first 1000 nulliparas delivered in 1988 who went into labor after 37 weeks' gestation with a single live fetus and cephalic presentation. The management of labor was standardized. As birth weight increased, there was an increase in the mean duration of labor and of the second stage of labor, in the incidence of oxytocin augmentation, and in the incidence of both cesarean and forceps delivery for dystocia. The direct relationship between birth weight and the mean duration of labor was independent of gestation and oxytocin augmentation. These findings suggest that birth weight is an important factor in the development of dystocia in nulliparas.

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.

Effects of high-dose oxytocin augmentation on umbilical cord blood gas values in primigravid women.

Active management of labor for term primigravid women with singleton, vertex presentations is associated with significant decreases in incidence of cesarean section and duration of labor, without adversely affecting major perinatal outcome variables. Concern has been expressed that high-dose oxytocin augmentation may increase the incidence of fetal compromise. With active management of labor, 43% of 1423 primigravid women received high-dose oxytocin augmentation during an 11-month period. Umbilical cord blood gas values from those who received high-dose oxytocin augmentation were compared with values in those who received no oxytocin. The mean arterial pH value in the no oxytocin group was 7.24 +/- 0.07, which is not significantly different (p greater than 0.10) from that of the oxytocin-augmented group, 7.23 +/- 0.07. Similarly, all other arterial and venous umbilical cord gas parameters were unaffected by high-dose oxytocin augmentation (p greater than 0.10). Our values were compared with other published values where labor was not managed according to the principles of active management of labor, and no differences were found. We report the largest series of cord blood pH values in primigravid women and conclude that there is no adverse effect of high-dose oxytocin augmentation or active management of labor on umbilical cord blood gas values at delivery.