Prolactin levels during labor.

To test the hypothesis that prolactin (PRL) plays a role in the hormonal events of labor, serum PRL levels in 15 normal secundigravidas were measured on 2 occasions 10-15 days before delivery, at the onset of labor, at cervical dilatation of 5 and 10 cm, at the time of delivery, and on the first, second, and fifth days postpartum. The mean level of PRL was 163 ng/ml +/- 26 ng/ml at the onset of cervical dilatation; it typically decreased with the progress of labor, reaching a value of 140 ng/ml +/- 21 ng/ml at the time of delivery. The differences during the various stages of labor, however, were not found to be statistically significant. Postpartum values were significantly lower (P less than 0.01) on the fifth day after parturition. It is therefore unlikely that PRL is involved in or influenced by the hormonal interplay that occurs during labor.     

Phospholipase A2 levels during labor

Determinations of phospholipase A2 activity 2 hours after spontaneous start of uterine contractions in 14 women showed higher values than immediately post partum. The reason of this increase of enzyme activity inducing prostaglandin synthesis is not known yet.     

Vasopressin levels during pregnancy and labor

Baseline plasma vasopressin concentrations were measured in 10 healthy women during a normal menstrual cycle, 97 normal women during pregnancy and 43 pregnant women hospitalized during the third trimester because of pregnancy-induced hypertension (PIH). Plasma vasopressin levels were also measured in 44 normal pregnant women in early labor and in 30 parturients at delivery. The random plasma vasopressin concentrations did not vary significantly between the nonpregnant women during the follicular phase (2.3 +/- 0.2 microU/ml) and luteal phase (2.2 +/- 0.3 microU/ml) or during the third trimester in normal pregnant women (2.0 +/- 0.2 microU/ml) or those with PIH (2.0 +/- 0.1 microU/ml). There was a significant reduction (p less than 0.01) in plasma vasopressin levels in the pregnant women during the first trimester (1.5 +/- 0.1 microU/ml) and second trimester (1.5 +/- 0.1 microU/ml) as compared to levels in nonpregnant and pregnant women in the third trimester. The mean plasma vasopressin levels in the pregnant women complaining of nausea were similar to those in the pregnant women without nausea. Plasma vasopressin levels in women during labor did not increase significantly over third-trimester-pregnancy concentrations during the first stage of labor (1.9 +/- 0.1 microU/ml) or at delivery (1.8 +/- 0.1 microU/ml). These cross-sectional measurements of maternal plasma vasopressin levels do not support a role for vasopressin in the development of PIH or in the initiation or maintenance of labor.     

The rise of serum creatinine levels during labor

Summary Serum creatinine, blood urea nitrogen and creatine phosphokinase were measured in 32 women during the last 3 weeks of pregnancy and, in a further 39 women, during and after labor. The serum creatinine increased from 61.9±0.9 to 69.8±1.8 μmol/l (mean±SEM) (P<0.05) in the third stage of labor and returned to normal by 72 h after delivery. The muscle creatine phosphokinase increased from 54±7 to 77±9.9 units (P<0.05) during the third stage and remained high (87±13.3 units) 72 h later. We conclude that these changes are due to muscle contraction and injury during delivery.     

分娩动因的研究进展

分娩动因是当今科学领域的一个难解之迷。异常的分娩发动如早产 ,过期产对围生儿可产生一定的危害 ,故分娩动因的研究是围生医学的一个重大课题。分娩动因有种属差异 ,目前虽然对啮齿类动物、反刍类动物及灵长类动物的分娩发动的机制有所了解 ,但由于缺乏适当的动物模型 ,对于人类自身的分娩发动的具体机制尚不清楚。目前认为人类的分娩动因较其它种属的分娩机制更为复杂 ,受母体 ,胎儿 ,胎盘单位的多种内分泌激素的共同调节。本文就这一领域的研究进展进行综述。1　妊娠期子宫收缩状态的分期　　在整个妊娠期子宫的收缩状态分为 4个时期[1,…     

Endogenous prostaglandins and the initiation of labor

An attempt to define the role of the prostaglandins in human parturition must necessarily be fragmentary at the present time. However, there is no doubt that considerable progress has been made during the last few years and that the prostaglandins have been established as important key intermediates in the complex hormonal and mechanical events integrated in the process. Improved chemical methods for the determination of prostaglandins in body fluids and tissues as well as some evidence of indirect nature have contributed to a better understanding of this complex problem.     

Serum hyaluronic acid levels during pregnancy and labor

OBJECTIVE: To study the changes in concentrations of serum hyaluronic acid in uncomplicated human pregnancies. METHODS: We determined the concentrations of serum hyaluronic acid, using a specific enzyme-linked immunosorbent assay, in 70 nonpregnant women, 250 women during their pregnancies, and 68 women at the time of parturition. Results were analyzed for statistical significance with Scheffé test for multiple comparisons. RESULTS: During pregnancy, mean (+/- standard deviation) serum hyaluronic acid levels were 11.4 +/- 4.5, 13.6 +/- 2.8, 20.6 +/- 1.5, and 46.9 +/- 7.9 ng/mL at 5-14 (n = 47), 15-26 (n = 46), 27-37 (n = 58), and 38-40 (n = 99) weeks' gestation, respectively. Pregnant women in labor (n = 68) had significantly higher levels (100.4 +/- 11.3 ng/mL) than did women at term but not in labor (P < .01). CONCLUSION: Maternal serum hyaluronic acid concentrations increase as pregnancy progresses and serum levels increase significantly at term. Hyaluronic acid may be associated with cervical ripening during parturition.     

分娩动因的研究进展

1　内分泌调控学说多年来 ,分娩发动的内分泌调控学说一直占主要地位。大量研究表明 :分娩发动是由于子宫平滑肌由非活跃状态进入活跃状态的过程 ,受多种内分泌激素的调控。其最终结果引起子宫体肌收缩及宫颈扩张 ,从而发动分娩。1 1　与分娩发动相关的激素　目前已发现多种激素与分娩发动有关[1] ,主要包括 :前列腺素 ,皮质醇激素 ,雌、孕激素 ,催产素等。其中前列腺素 (ＰＧｓ)作用一直倍受关注和肯定。主要证据包括 :①分娩前子宫、羊水及胎膜等组织中ＰＧｓ明显升高 ;②临床应用外源性的前列腺素可引起宫颈成熟及子宫收缩 ,诱发分娩 ;③…     

Plasma oxytocin in initiation of labor

Serial radioimmunoassay measurements of plasma oxytocin (OT) in maternal venous blood have been carried out in 15 patients, during pregnancy, labor, and delivery. Fetal plasma OT was also measured in the blood from the umbilical vein and umbilical artery. The results indicate that: (1) during pregnancy, plasma OT is present in maternal blood; (2) the quantity of plasma OT increases with advancing pregnancy; (3) no OT surge occurs around the onset of labor; (4) the plasma OT surge occurs with cervical dilatation and vaginal distention. The data indicate that OT does not play a primary role in the initiation of labor and support the concept that OT most likely contributes to formation of prostaglandins through the uterine contractions OT produces. OT surges, frequently called spikes, have been observed to occur during pregnancy as well as during labor. During the course of labor, OT surges have been encountered in association with rupture of the membranes, vaginal examination, and descent of the vertex, and have occurred almost consistently with maximal cervical and vaginal distention. Such OT surge was suppressed by effective spinal and pelvic regional anesthesia. Therefore, this surge is consistent with the Ferguson reflex described in experimental animals, and it represents the first evidence that the Ferguson reflex, in fact, exists in human beings. Evidence is presented here that an excess of OT in fetal blood over that found in maternal plasma was associated with hypertonic, irregular, tumultuous or prolonged labor and with mild to moderate fetal hypoxia and fetal distress peculiar to abnormal uterine contractions.     

Human placental lactogen levels during and after labor.

In order to estimate the human placental lactogen (HPL) level and its value as an indicator of fetoplacental function during labor, we determined HPL levels (N equals 225) before, during, and after labor in normal (N equals 16) and preeclamptic (N equals 14) subjects or in patients with benign intrahepatic cholestasis of pregnancy (N equals 5). During labor, greater decreases in this value were found in preeclamptic than in normal subjects and similarly in mothers with fetoplacental dysfunction than with normal fetoplacental function. The rupture of the membranes had no effect on the level of HPL, which was not related to parity, oxytocin infusion, time interval from rupture of the membranes to delivery, nor to relative placental weight. The half-life of HPL varied in the range of 20-23 minutes immediately after delivery and in the range of 30-39 minutes some time later. During labor, greater decreases in HPL level in cases of preeclampsia or fetoplacental dysfunction may be caused by relative uteroplacental ischemia during uterine contractions, but from this finding it is hard to expect any advantage of HPL as a monitor of fetoplacental function during labor.     

Epidural analgesia during labor and delivery: effects on the initiation and continuation of effective breastfeeding.

This prospective cohort study examined the association between epidural analgesia during labor and delivery, infant neurobehavioral status, and the initiation and continuation of effective breastfeeding. Healthy, term infants delivered vaginally by mothers who received epidural analgesia (n = 52) or no analgesia (n = 63) during labor and delivery were assessed at 8 to 12 hours postpartum, followed by a telephone interview with the mothers at 4 weeks postpartum. There was no significant difference between the epidural analgesia and no-analgesia groups in breastfeeding effectiveness or infant neurobehavioral status at 8 to 12 hours or in the proportion of mothers continuing to breastfeed at 4 weeks. Therefore, epidural analgesia did not appear to inhibit effective breastfeeding. There was a positive correlation between infant neurobehavioral status and breastfeeding effectiveness (Spearman rho = 0.48, P = .01), suggesting that neurobehavioral assessment may prove beneficial in identifying infants at greater risk for breastfeeding difficulties.     

The relationship between beta-endorphin levels and uterine muscle contractions during labor

Plasma beta-endorphin (BE) levels (8.6 +/- 0.8 pmol/l) (mean +/- SE) were lower in the third trimester than in non-pregnant controls (14.8 +/- 1.1 pmol/l) (P less than 0.001), increased during labor, to 29.3 +/- 4.4 pmol/l (P less than 0.005) and decreased, 72 h after delivery, to 3.5 +/- 0.4 pmol/l (P less than 0.001). BE levels were found to correlate significantly with uterine muscle contraction (r = 0.966, P less than 0.05) and with cervical effacement (r = 0.974, P less than 0.05) during labor.     

Oxytocin and the initiation of human parturition. I. Prostaglandin release during induction of labor by oxytocin

Concentrations of plasma prostaglandins E and F and the 15-keto-13,14 dihydrometabolite of PGF2 alpha (PGFM) were determined by radioimmunoassay in 15 women who underwent induction of labor with oxytocin. Plasma PGFM rose significantly during the oxytocin infusion in nine women who went on to deliver vaginally but did not change in six women in whom induction of labor failed. Plasma PGE and PGF levels also rose during the infusion in the nine women with successful induction of labor but the changes were not statistically significant. In comparison to the six women in whom induction failed, however, plasma PGE in the nine women with successful induction reached significantly higher levels. Oxytocin infusions elicited uterine contractions of similar frequency in both groups of women, but the cervix failed to dilate in the six women in whom induction failed. The oxytocin-induced rise in plasma PGFM is, therefore, not simply a consequence of uterine contractions. We suggest that oxytocin stimulates PGF production in the pregnant uterus when it is appropriately sensitized to oxytocin, causing a potentiation of the oxytocin-induced contractions which is necessary for the contractions to become efficient in dilating the cervix. We further suggest that the stimulation of PGF production by oxytocin is mediated by oxytocin receptors, probably in the decidua.     

Effect of intrathecal morphine during labor on maternal plasma β-endorphin levels

Plasma β-endorphin was measured in 16 patients in labor prior to and after complete onset of analgesia with 1 mg of morphine administered intrathecally. Human β-endorphin levels were determined by radioimmunoassay following silicic acid extraction of plasma samples and separation of the β-endorphin fraction by gel chromatography. Plasma β-endorphin levels decreased significantly (p < 0.005) after intrathecal morphine from 76 ± 9.7 to 46.3 ± 9.1 fmol/ml (mean ± SE), possibly because of decreased pituitary β-endorphin secretion in response to alleviation of labor pain.