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PubMed1991

The current status of intrapartum continuous fetal tissue pH measurements.

Continuous tissue pH monitoring during labor has now been possible for 15 years. Tissue pH is measured in the intercellular fluid, and the value differs in some cases from the blood pH value because of local capillary flow and local metabolism. The fetal scalp seems to be an area where tissue pH and capillary blood pH values are very close, but in acute acidosis there may be a time lag of 10-15 min before tissue pH is equilibrated. Normal values of scalp tissue pH are 7.38 in early labor declining by 0.016 per hour during the first stage of labor and by 0.12 per hour during the second stage of labor. Tissue pH values below 7.15 are defined as pathological. The correlation coefficient to umbilical artery blood pH (0.71), success rate (67%) and electrode drift (below 0.04) from the largest study of tissue pH monitoring using glass pH electrodes (n = 337) are described.

Acid-Base Equilibrium↗
PubMed1995

Doppler velocimetry of the fetal middle cerebral artery in patients with preterm labor and intact membranes.

A prospective cohort study was conducted to determine whether preterm labor is associated with changes in the impedance to blood flow of the fetal middle cerebral artery. Doppler velocimetry studies were performed in 194 consecutive patients with preterm labor and intact membranes. Pulsatility indices of the middle cerebral artery and umbilical artery were determined on admission. Results were expressed as ratio of the observed pulsatility index to mean value for gestational age expressed as delta MCA PI and delta UA PI, respectively. The prevalence of preterm delivery (< 37 weeks) and delivery within 24 hours of admission was 55.2% (107/194) and 15.5% (30/194), respectively. Patients with an examination-to-delivery interval within 24 hours had significantly lower mean delta MCA PI than that of patients delivered at > or = 37 weeks and > or = 4 weeks after the examination (P < 0.01). Fetuses with a delta MCA PI at or below 0.88 had a relative risk of 2 (95% confidence interval, 1.32 to 2.9) who were delivered within 24 hours compared to controls (sensitivity 76.7%, specificity 62.8%, positive predictive value 26.7%, negative predictive value 93.5%). Stepwise logistic regression analysis indicated that the relationship between delta MCA PI and examination-to-delivery interval remained statistically significant after correcting for cervical dilatation (P < 0.001). Our data indicate that preterm parturition is associated with a decrease in the impedance to flow in the fetal cerebral circulation.

Adult↗
PubMed1980

Biodynamics of the cervical dilatation in human labor.

We recorded the pressure between the fetus and birth canal (PFB) with small strain-gauge type pressure transducers in 37 cases of human labor and estimated expulsive activity for evaluation of the expulsive forces. Expulsive activity increased progressively in conjunction with cervical dilatation and markedly increased after rupture of the membranes. At less than 200 Hashimoto units of expulsive activity, the cervical canal could not be dilated and labor was prolonged in all periods of the first stage of labor. There were three types of modes of changes in the expulsive activities at three points on the cervical canal. These three types had different clinical characteristics of cervical dilatation during labor. New parameters such as the expulsive effort, efficiency index and resistance index of the uterine cervix, estimated together with the expulsive activity, were proposed in an attempt to evaluate the effect of expulsive forces on cervical dilatation.

Amnion↗
PubMed2002

Chronobiology of epidural ropivacaine: variations in the duration of action related to the hour of administration.

BACKGROUND: A temporal pattern of the kinetics of local anesthetics is demonstrated in dental and skin anesthesia, with an important variation in the duration of action related to the hour of administration. The aim of this study is to determine whether the hour of injection influences the duration of epidurally administered ropivacaine during labor. METHODS: One hundred ninety-four women in the first stage of labor were assigned to one of four groups throughout the day period: group 1 (night: from 1:01 to 7:00 am), group 2 (morning: from 7:01 am to 1:00 pm), group 3 (afternoon: from 1:01 to 7:00 pm), and group 4 (evening: from 7:01 pm to 1:00 am). Each patient received 14 ml ropivacaine, 0.17%, epidurally, and analgesia duration was measured. RESULTS: Pain assessed by a visual analog score was not differ-ent among groups before the first injection of local anesthetic. Analgesia duration was greater in the diurnal period (group 2: 110 +/- 25 min and group 3: 117 +/- 23 min) compared with the nocturnal period (group 1: 94 +/- 23 min and group 4: 91 +/- 23 min) (P < 0.01). The largest intraday variation of analgesia duration among groups reached 28%. CONCLUSIONS: Epidural analgesia duration exhibits a temporal pattern with important differences among diurnal and nocturnal phases. The authors emphasize that the lack of consideration of the chronobiologic conditions in epidural analgesia studies may create significant statistical bias. Future studies dealing with epidural local anesthetics should consider the time of drug administration.

Adult↗
PubMed2005

Randomized controlled trial of hands-and-knees positioning for occipitoposterior position in labor.

BACKGROUND: Hands-and-knees positioning during labor has been recommended on the theory that gravity and buoyancy may promote fetal head rotation to the anterior position and reduce persistent back pain. A Cochrane review found insufficient evidence to support the effectiveness of this intervention during labor. The purpose of this study was to evaluate the effect of maternal hands-and-knees positioning on fetal head rotation from occipitoposterior to occipitoanterior position, persistent back pain, and other perinatal outcomes. METHODS: Thirteen labor units in university-affiliated hospitals participated in this multicenter randomized, controlled trial. Study participants were 147 women laboring with a fetus at >or=37 weeks' gestation and confirmed by ultrasound to be in occipitoposterior position. Seventy women were randomized to the intervention group (hands-and-knees positioning for at least 30 minutes over a 1-hour period during labor) and 77 to the control group (no hands-and-knees positioning). The primary outcome was occipitoanterior position determined by ultrasound following the 1-hour study period and the secondary outcome was persistent back pain. Other outcomes included operative delivery, fetal head position at delivery, perineal trauma, Apgar scores, length of labor, and women's views with respect to positioning. RESULTS: Women randomized to the intervention group had significant reductions in persistent back pain. Eleven women (16%) allocated to use hands-and-knees positioning had fetal heads in occipitoanterior position following the 1-hour study period compared with 5 (7%) in the control group (relative risk 2.4; 95% CI 0.88-6.62; number needed to treat 11). Trends toward benefit for the intervention group were seen for several other outcomes, including operative delivery, fetal head position at delivery, 1-minute Apgar scores, and time to delivery. CONCLUSIONS: Maternal hands-and-knees positioning during labor with a fetus in occipitoposterior position reduces persistent back pain and is acceptable to laboring women. Given this evidence, hands-and-knees positioning should be offered to women laboring with a fetus in occipitoposterior position in the first stage of labor to reduce persistent back pain. Although this study demonstrates trends toward improved birth outcomes, further trials are needed to determine if hands-and-knees positioning promotes fetal head rotation to occipitoanterior and reduces operative delivery.

Adolescent↗
PubMed2000

[Risk factors and neonatal outcomes in shoulder dystocia].

BACKGROUND: Shoulder dystocia (SD) is a rare obstetrical complication but linked with a high perinatal morbidity and mortality rate. SD has been associated to a series of maternal and fetal risk factors due to a multifactorial etiology. This study analyzes the incidence of SD, its morbidity and associated risk factors. METHODS: Cases of SD occurred at the St. Gerardo Hospital (Monza) between January 1992 trough December 1997 have been retrospectively reviewed. Obstetrical and feto-neonatal data regarding cases of SD were compared to data regarding all the cephalic vaginal deliveries occurred in the same period in our Center. RESULTS: A total of 14,157 cephalic vaginal deliveries were included in this study, of these 21 infants (0.15%) had SD. A significantly higher incidence of SD cases was found in fetal macrosomia, maternal diabetes, induction of labor by PGE2, use of obstetrical vacuum, length of first stage of labor > 4 hours in multiparas and > 8 hours in nulliparas, and length of second stage > 60 minutes, regardless of parity. A closed association was also observed between SD and birth trauma as brachial plexus injury and humerus fracture. CONCLUSION: The incidence of SD in our population (0.15%) is below the average reported in the literature (0.37-1.1%). The well-known risk factors, whose low positive predictive value can nevertheless modify obstetrical management, are confirmed.

Algorithms↗
PubMed1994

The effect of labor on the normal values of umbilical blood acid-base status.

BACKGROUND: Although several investigators have attempted to define the normal values of umbilical cord blood pH and gases, there is considerable controversy about the optimal cutoff values to diagnosis intrauterine asphyxia. A possible reason for this might be that several studies have included data from fetuses born after different duration of labor. OBJECTIVE: To determine the effect of labor and the duration of second stage on labor on umbilical arterial acid-base status at birth in healthy term infants. METHODS: Umbilical artery acid-base status was determined in patients (n = 356) who met the following criteria: 1) singleton term pregnancy with no significant medical, obstetric, or neonatal complications; 2) vertex presentation if delivered vaginally; 3) neither regional nor general anesthesia applied if delivered vaginally; 4) no use of oxytocin; 5) normal fetal heart rate patterns; 6) clear amniotic fluid; 7) Apgar scores at 1 and 5 min > or = 7; 8) appropriate fetal weight for gestational age. Patients were divided into three groups. A-patients delivered by cesarean section (CS) in the absence of labor (n = 135); B-patients delivered by CS during first stage of labor (n = 62); C-patients with vaginal birth (n = 159). A Kruskal-Wallis ANOVA with post-hoc procedures and stepwise multiple regression analysis were performed. RESULTS: 1) There were significant differences in cord arterial acid-base values between study groups (pH: no labor CS, 7.27 +/- 0.05 vs labor CS, 7.26 +/- 0.05 vs vaginal birth, 7.24 +/- 0.07, p < 0.00001). 2) There was a significant fall in cord arterial pH and bicarbonate concentrations with increased duration of second stage of labor in newborns born vaginally (pH: duration of second stage, 1-30 min, 7.25 +/- 0.07 vs 31-60 min, 7.22 +/- 0.06 vs > 61 min, 7.21 +/- 0.07, p < 0.05). 3) Analysis of confounding variables which could influence the cord pH such as parity, use of vacuum, gestational age, maternal age, and birth weight by stepwise multiple regression analysis indicated that only the duration of second stage of labor pain had a significant relationship with cord blood pH. CONCLUSION: There is a significant fall in umbilical artery pH and bicarbonate with the presence of labor and increased duration of second stage of labor in healthy term neonates. This should be taken into consideration in evaluating neonatal well-being by cord blood pH and acid-base measurements.

Analgesia, Obstetrical↗
PubMed2000

Relationship between the length of the perineum and position of the anus and vaginal delivery in primigravidae.

The aim of the study was to determine perineal length and anal position in primigravidae and to evaluate their effect on vaginal delivery. The distances between the fourchette and each of the center of the anal orifice and the inferior margin of the coccyx were measured in 212 primigravidae with singleton term pregnancies during the first stage of labor. Anal position index was calculated by dividing the first measurement by the second. The mean +/- SD length of perineum was 4.6 +/- 0.9 cm. The mean +/- SD anal position index was 0.49 +/- 0.12. Women with a short perineum (<4 cm) or a small anal position index (<0.42) had significantly higher rates of episiotomy, perineal tears and instrumented delivery. This association was also significant by multiple logistic regression analysis. It was concluded that a short perineum and anterior displacement of the anus were associated with traumatic vaginal delivery in primigravidae.

Adult↗
PubMed1989

Source of increased plasminogen activators during pregnancy and puerperium.

We investigated the increase of plasminogen activators (tPA and uPA) in the plasma during pregnancy. Both tPA and uPA antigens were found to increase after the third trimester of pregnancy and high levels of PAs persisted through the first stage of labor. The tPA antigen levels rose further for the first few hours post-partum, while the level of uPA antigen returned to normal immediately following childbirth. To clarify whether the uterus and/or placenta are involved in the increased levels of plasma PAs, the levels were measured in uterine venous blood in cases of caesarean sections. During the ante-partum period, the level of uPA antigen in the uterine venous blood was higher than that in the peripheral venous blood, while there was no significant difference between the levels of tPA antigen in peripheral blood and uterine venous blood. The level of tPA antigen in the uterine venous blood rose after delivery. In contrast, the level of uPA antigen declined immediately after delivery. These results suggest that (1) the placenta is the major source of the increased uPA antigen during pregnancy, (2) entire vascular system is involved in the increased tPA antigen during pregnancy, (3) a further increase in tPA after delivery is due to the release of this enzyme from the involuting uterus.

Antigens↗
PubMed1994

Nitrous oxide in early labor. Safety and analgesic efficacy assessed by a double-blind, placebo-controlled study.

BACKGROUND: Intermittent self-administered nitrous oxide has long had widespread use as an analgesic in labor, but its efficacy has not been adequately established. Questions about its effect on maternal oxygenation between labor contractions also have been raised. METHODS: Twenty-six women were recruited to participate in a randomized, double-blind, cross-over, placebo-controlled study to assess the effect of intermittent nitrous oxide inhalation on labor pain and maternal hemoglobin oxygen saturation (SPO2) during the first stage of labor. Visual analog scale pain scores for each of five consecutive labor contractions were measured after administration of either nitrous oxide or compressed air. RESULTS: Mean visual analog scale pain scores for five contractions were 5.1, 5.2, 5.7, 5.2, and 5.6 (nitrous oxide) and 4.9, 5.2, 6.1, 5.6, and 5.7 (compressed air). There were no statistically significant differences in pain when nitrous oxide as compared with compressed air was administered. Pain scores did not differ significantly over time as a function of inhaled substance (F = 0.41, P = 0.53). The mean lowest SPO2 observed between these contractions after self-administration of nitrous oxide and air were 97, 97, 97, 97, and 97% (nitrous oxide) and 97, 96, 96, 96, and 96% (compressed air). SPO2 was significantly higher after nitrous oxide administration (F = 8.8, P = 0.007). CONCLUSION: While intermittent self-administered 50% nitrous oxide in oxygen does not appear to predispose parturient women to hemoglobin oxygen desaturation, its analgesic effect has yet to be clearly demonstrated.

Adult↗