Frequency Of Uterine Contractions Research Articles

Interleukin-8 potentiates the effect of interleukin-1-induced uterine contractions.

The aim of this research was to study the effect of exogenous interleukin (IL)-8, IL-1 and IL-8 + IL-1 on uterine contractions in rabbits. Four equal groups of non-pregnant rabbits (n = 24) were investigated using either placebo or experimental drugs in the form of vaginal suppositories. The suppositories contained human recombinant IL-8 (200 ng), IL-1 (200 ng), IL-8 (200 ng) + IL-1 (200 ng) or vehicle Witepsol base, 500 microliters). Subsequently, the plasma concentration of prostaglandin (PG) E2 was estimated 3 h after the last dose of treatment. Neutrophil infiltration in the endometrial tissue was studied with anti-rabbit RT2 staining. Suppositories with IL-1 and IL-8 + IL-1 produced contractile responses with increased frequency (P < 0.003, P < 0.0005) and amplitude (P < 0.0001) in vivo, compared with vehicle. IL-1 and IL-8 + IL-1 also caused similar contractile effects with increased frequency (P < 0.01, P < 0.0007) and amplitude (P < 0.0001) in an in-vitro experiment than vehicle. The frequency and amplitude of uterine contractions were more significant with IL-8 + IL-1 than that of IL-1, both in vivo (P < 0.002, P < 0.05) and in vitro (P < 0.005, P < 0.01). IL-8 did not induce any contractions. Prostaglandin concentration was increased approximately 8-fold with IL-8 + IL-1 (P < 0.0001) and 2.5-fold with IL-1 treatment (P < 0.0001). Neutrophil numbers were significantly increased with IL-8 + IL-1 > IL-8 > IL-1 (P < 0.002, P < 0.0003 and P < 0.008) compared with vehicle. Our data suggest that IL-8 stimulates IL-1-induced uterine contractions through PGE2 production and could be an important process during labour and delivery.

Uterine contractions at the time of embryo transfer alter pregnancy rates after in-vitro fertilization.

To investigate the possible consequences of uterine contractions (UC) as visualized by ultrasound (US) on in-vitro fertilization (IVF)-embryo transfer outcome, we studied prospectively 209 infertile women undergoing 220 cycles of controlled ovarian stimulation. Inclusion criteria were age < or = 38 years, a morphologically normal uterus, and at least three good quality embryos transferred. Just before embryo transfer, women underwent 5 min digital recordings of the uterus using US image analysis software for UC assessment. Plasma progesterone and oestradiol concentrations were measured. Four groups were defined according to UC frequency: < or = 3.0 (n = 53), 3.1-4.0 (n = 50), 4.1-5.0 (n = 43), and > 5.0 (n = 74) UC/min respectively. Patients, controlled ovarian hyperstimulation and embryology characteristics were comparable in all groups. A stepwise decrease in clinical and ongoing pregnancy rates as well as in implantation rates occurred from the lowest to the highest UC frequency groups (53, 36, 21; 46, 32, 20; 23, 19, 10; and 14, 11, 4%; P < 0.001). Plasma progesterone and UC frequency were negatively correlated (r = -0.34, P < 0.001). Direction of UC did not affect embryo transfer outcome. As this study was controlled strictly for confounding variables and UC were assessed objectively by a computerized system, its results indicate that high frequency UC on the day of embryo transfer hinder IVF-embryo transfer outcome, possibly by expelling embryos out of the uterine cavity. The negative correlation between UC frequency and progesterone concentrations supports the uterine relaxing properties of progesterone.

The role of nitric oxide and its donors in uterus contractility regulation

This article presents comprehensive data on uterine contractility regulation by nitric oxide, including systematized contemporary data on the status and function of the human nitroxidergic vasodilator system, and our experience in threat of pregnancy interruption management by nitroglycerin given with the transdermal therapeutic system Deponit 5 (Schwarz Pharma, Germany). To control contractile uterine activity in pregnant women with pathologic preliminary period, the authors successfully used sublingual application of Nitrolingual aerosol (G. Pohl-Boskamp GmbH and Co, Germany) with prolongation of the effect by the Deponit system 5. As little as five minutes after aerosol application tocography revealed a decrease in uterine contraction frequency, duration and intensity. By effecting post- and preloading and lowering the resistance of spiral arteries, vasodilators provided increased intensity of placenta circulation, which had a great importance for anteintranatal care of the fetus and newborn. The advantages of nitric oxide donator application in obstetrics were also demonstrated.

Effects of nomegestrol acetate on spontaneous and sulprostone-induced uterine contractions in pregnant cynomolgus monkeys monitored by telemetry

OBJECTIVE: Our purpose was to study the effects of the progestomimetic compound nomegestrol acetate on spontaneous and sulprostone-induced uterine contractility in pregnant cynomolgus monkeys. STUDY DESIGN: Intrauterine pressure was continuously monitored with use of an implanted intraamniotic catheter and a telemetric pressure transmitter from day 115 to 135 of gestation (term = 165 days). After surgery the animals received either nomegestrol acetate (5 mg per day orally, n = 3) or vehicle only (controls, n = 3). The intramuscular prostaglandin E 2 analog sulprostone (25 μg) was administered as a single injection 10 days after amniotic catheter implantation. Spontaneous and sulprostone-induced uterine contractions were compared between nomegestrol acetate– and vehicle-treated animals. RESULTS: The frequency of spontaneous uterine contractions in control animals demonstrated a 24-hour pattern with a minimum at 12 hours and a maximum at 0 hours. The frequency of spontaneous contractions did not differ between nomegestrol acetate– and vehicle-treated animals. Sulprostone induced an increase in both the frequency and amplitude of contractions, reaching a maximum 12 hours after injection and fading out after 24 hours in vehicle-treated animals. In animals receiving nomegestrol acetate, the frequency of contractions increased moderately and transiently for a total duration of 6 hours only and returned to control levels thereafter. CONCLUSIONS: Nomegestrol acetate significantly decreases the contractile response of the pregnant uterus induced by the prostaglandin E 2 analog sulprostone. (Am J Obstet Gynecol 1998;178:150-5.)

Inhibition of xylazine induced uterine contractility by clenbuterol and nifedipine

A study was undertaken in order to determine the effects of xylazine on uterine contractility in goats premedicated with clenbuterol or nifedipine. These drugs inhibit uterine activity by acting as potent tocolytic or uterine relaxant agents. A balloon-tipped catheter was inserted under sedation and local anaesthesia on to a uterine horn in 15 cycling goats in order to record intrauterine pressure changes. Three groups of five goats were used: group I was treated With an intravenous dose of 0·1 mg kg −1 of xylazine. Groups II and III were pretreated with 4 μg kg −1 of clenbuterol and 80μg kg −1 of nifedipine, respectively, before administrating the same dose of xylazine. Xylazine increased the frequency and intensity of uterine contractions significantly and the value of the area under the contraction curves was significantly higher than that observed under basal conditions i.e. before drug treatment. In goats premedicated with clenbuterol or nifedipine, the uterotonic effects of xylazine (2858±217 versus basal contractility: 1241±173 mm 2·5 min −1, P <0·05) were inhibited for the 30 minutes recording period. These data indicate that clenbuterol and nifedipine can be used as potent tocolytic agents in order to prevent the uterine side effects of xylazine.

Antenatal patterns of uterine activity in low-risk women: a longitudinal study.

There is a surprising lack of information on antenatal patterns of uterine activity in the normal obstetric population, with the majority of research having focussed on women at high-risk for preterm birth. We conducted a prospective longitudinal study to investigate patterns of uterine activity in women with singleton gestations at low-risk for preterm birth. Twenty pregnant women were recruited and their uterine activity was recorded using ambulatory tocodynamometry twice weekly throughout the latter half of pregnancy. The collected data were transmitted to a central receiving station for analysis. As gestation advanced there was a progressive increase in the median number of contractions detected per hour, peaking and stablizing at 37-40 weeks (median of 0 contractions/hour at 20-24 weeks rising to 5.4 contractions/hour at 37-40 weeks). In those women with uterine activity, contraction duration and amplitude of deflection significantly increased as gestation advanced. There was a progressive increase in the number of higher amplitude contractions throughout the third trimester. Increasing parity was not associated with increasing antenatal uterine contraction frequency. No association between normal daily physical activity and uterine contraction frequency was evident throughout gestation. In normal human pregnancy there is a steady, progressive increase in the frequency, duration and amplitude of antenatal uterine activity throughout the latter half of gestation. The uterine contractile profile alters from one of a low amplitude, low frequency pattern in the second trimester to a higher amplitude, higher frequency pattern at term.

Rapid fetal fibronectin swab-test in preterm labor patients treated by betamimetics

Objective: A preliminary study to examine the value of a rapid fetal fibronectin swab-test used as a bedside test in the prognosis of preterm labor. Study design: Women presenting with preterm labor and intact membranes and less than 3 cm dilated were enrolled in a single referal center. Cervicovaginal swabs were assessed for the presence or absence of fetal fibronectin by means of a rapid monoclonal antibody assay the positivity of which was revealed by a colorimetric reaction. Results were compared with uterine contractions frequency, Bishop cervical score, duration of tocolysis and interval to delivery. The predictive value of fetal fibronectin test for delivery within 7, 14 or 21 days from sampling and before 32 and 37 weeks' of gestation was assessed in the two groups. Results: Among 124 eligible patients, 19 presented with a positive fibronectin test and 105 with a negative one. Gestational age at sampling. Bishop cervical score and duration of tocolysis were identical in the two groups. The number of contractions was significantly lower and gestational age at delivery was significantly higher in the fibronectin negative group. Fetal fibronectin in cervicovaginal secretions has a high sensitivity (89%) for delivery within 7 days. Absence of fetal fibronectin in cervicovaginal secretions of patients presenting with uterine contractions could rule out preterm labor within 7 and 14 days with a predictive value of 99 and 95.2%, respectively. In negative fetal fibronectin patients, preterm delivery before 32 and 37 weeks' is unlikely to occur with a predictive value of 97 and 85%, respectively. Conclusion: Cervicovaginal fetal fibronectin detected by a rapid bedside swab-test in women with symptoms of preterm labor compares favourably with quantitative assays and could prove useful in the management of preterm labor. This should be confirmed in a longer prospective study.

Maternal prolactin secretion is phasic during induced term and post-term labor

We hypothesized that regimens of labor induction do not alter the biphasic secretion of maternal prolactin (PRL) seen during spontaneous labor. Serial blood samples drawn from 12 women before, during, and after induced labor were assayed for PRL and hCG and compared with cervical dilatation and uterine contraction frequency (UCF). Induction methods were cervical ripening with dinoprostone gel (Prepidil) followed by oxytocin infusion (n = 1), amniotomy followed by oxytocin (n = 4), oxytocin followed by amniotomy (n = 3), amniotomy only (n = 2), and oxytocin only (n = 2). Regardless of the induction method, PRL decreased with advancing cervical dilatation during the first stage of labor and reached a nadir at full dilatation. Prolactin levels then increased rapidly during the second stage, correlating significantly with the increase in UCF, and peaked at 1 hour postpartum before decreasing. Levels of hCG increased during labor and peaked just before or at delivery before rapidly decreasing. The biphasic secretion of maternal PRL is a fundamental characteristic of active term labor and occurs regardless of the method used to induce labor.

Uterine activity after induction of hypocalcaemia in the ovariectomized camel (Camelus dromedarius).

Bilateral ovariectomy was performed in three parous, non-pregnant camels. Intrauterine and intraabdominal pressure changes were recorded using balloon-tipped catheters. Uterine contractions were induced and maintained in the ovariectomized camels by daily intramuscular injections of 5 mg oestradiol benzoate throughout the experimental period. The frequency of uterine contractions varied from 6 to 9 per minute, whereas the amplitude varied from 2 to 3 kPa in all the animals. Inducing hypocalcaemia to a level of 0.5 mmol/L by Na2EDTA reduced the amplitude of the contractions to below 1 kPa (p < 0.001). The frequency of the contractions was not affected.

Correlation of antepartum uterine activity and cervical change in twin gestation.

To determine the correlation between quantitative measurements of antepartum uterine activity and cervical change twin gestations. Forty women from our Twin Clinic constituted the study group. Participants had a cervical examination each week between 20 and 37 weeks gestation and a cervical score (CS) was calculated as follows: CS = cervical length (cms)-cervical dilation (cms) at the internal os. The women also performed blinded home uterine activity monitoring (HUAM) for a mean of 7.0 + 3.0 hrs/wk (+SD). Uterine activity was expressed as mean number of contractions/hour/week gestation based on the average of three independent reviewers. CS was determined by a single clinician unaware of the HUAM recordings. A significant change in the CS was defined as a reduction of at least 0.5 from the preceding week. Correlation coefficients were used to determine the association between uterine activity and change in the cervical score. Twin pregnancy was characterized by a rise from 0.2 + .03 contractions/hr at 20 weeks to 3.2 + 2.4 contractions/hr at 37 weeks gestation. CS fell from a mean of 2.6 + 0.2 at 20 weeks to -2.1 + 0.9 at 37 weeks gestation. There was a significant negative correlation (-0.317, p < .0001) between increasing uterine activity and decreasing CS. There were significantly more (p < .002) contractions during the 7 days preceding a significant reduction in CS (3.3 + 3.5 contractions/hr) than when the CS was unchanged (1.6 +/- 1.5 contractions/hr). In twin gestations, an increasing frequency of uterine contractions is strongly correlated with quantifiable cervical change between 20-37 weeks gestation. Persistent daytime contraction frequencies of > 3/hr represent a risk factor for cervical dilation and/or effacement.

Fetal cerebral oxygenation and hemodynamics during labour measured by near‐infrared spectroscopy

The failure of modern fetal monitoring techniques to measure either oxygenation or perfusion within the fetal brain may underlie their poor specificity in the detection of intrapartum hypoxia-ischaemia. We have adapted the technique of near-infrared spectroscopy (NIRS) to obtain continuous, quantified measurements of changes in human fetal cerebral oxygenation and blood volume during labour. More than 140 fetuses have been studied at University College London for periods ranging from 10 to 765 minutes. Reciprocal changes in the cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, indicating changing cerebral haemoglobin saturation, have been observed during uterine hyperstimulation with oxytocin, administration of maternal oxygen, changing maternal posture, and late fetal heart rate decelerations. Uterine contraction frequency greater than 1 every 2 minutes was associated with a fall in fetal cerebral oxygenation. A method for quantifying the oxygen saturation of hemoglobin derived from all vascular compartments (SmcO2) is described. There was a significant positive correlation between SmcO2 and umbilical artery pH. Conversely, the base deficit of blood from the umbilical artery showed a negative correlation with SmcO2. Changes in optical pathlength due to probe movement during uterine contractions are a potential source of error in the measurements. Preliminary data obtained using intensity modulated optical spectrometry, a technique that continuously measures optical pathlength, suggest that the maximum contribution of movement artifact to observed changes in chromophore concentration is 12%. These preliminary data demonstrate that NIRS is capable of measuring fetal cerebral oxygenation and blood volume during labour. However, because none of the fetuses in this study was born with evidence of intrapartum hypoxia-ischaemia, we cannot comment on the value of NIRS as a means of intrapartum surveillance. Further developments, including the routine use of IMOS and rigorous testing by randomized trials, will be required before this question is answered. MRDD Research Reviews 3:59–68, 1997. © 1997 Wiley-Liss, Inc.

Fetal cerebral oxygenation and hemodynamics during labour measured by near-infrared spectroscopy

The failure of modern fetal monitoring techniques to measure either oxygenation or perfusion within the fetal brain may underlie their poor specificity in the detection of intrapartum hypoxia-ischaemia. We have adapted the technique of near-infrared spectroscopy (NIRS) to obtain continuous, quantified measurements of changes in human fetal cerebral oxygenation and blood volume during labour. More than 140 fetuses have been studied at University College London for periods ranging from 10 to 765 minutes. Reciprocal changes in the cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, indicating changing cerebral haemoglobin saturation, have been observed during uterine hyperstimulation with oxytocin, administration of maternal oxygen, changing maternal posture, and late fetal heart rate decelerations. Uterine contraction frequency greater than 1 every 2 minutes was associated with a fall in fetal cerebral oxygenation. A method for quantifying the oxygen saturation of hemoglobin derived from all vascular compartments (SmcO2) is described. There was a significant positive correlation between SmcO2 and umbilical artery pH. Conversely, the base deficit of blood from the umbilical artery showed a negative correlation with SmcO2. Changes in optical pathlength due to probe movement during uterine contractions are a potential source of error in the measurements. Preliminary data obtained using intensity modulated optical spectrometry, a technique that continuously measures optical pathlength, suggest that the maximum contribution of movement artifact to observed changes in chromophore concentration is 12%. These preliminary data demonstrate that NIRS is capable of measuring fetal cerebral oxygenation and blood volume during labour. However, because none of the fetuses in this study was born with evidence of intrapartum hypoxia-ischaemia, we cannot comment on the value of NIRS as a means of intrapartum surveillance. Further developments, including the routine use of IMOS and rigorous testing by randomized trials, will be required before this question is answered. MRDD Research Reviews 3:59–68, 1997. © 1997 Wiley-Liss, Inc.

THE EFFECT OF THIOLA, PIROXICAM AND DILTIAZEM ON THE UTERINE CONTRACTILITY OF γ-IRRADIATED RATS

Accidental radiation exposure raises concern for functional modifications in the uterine physiology. In the current work, total body γ-irradiation (0.7, 1.4 and 2.1 Gy) of non-pregnant adult female albino rats increased significantly the frequency and amplitude of uterine contractions in vivo. Administration of Thiola (a sulfhydryl containing agent) in doses of 100 or 250mgkg −1, pre-irradiation, or Piroxicam (a potent prostaglandin inhibitor) in a dose of 2mgkg −1, pre- or post-irradiation failed to normalize the changes induced by γ-irradiation. However, administration of Diltiazem (a Ca 2+channel blocker, 8mgkg −1) pre- or post-irradiation caused a significant decrease in the frequency of uterine contractions (21% and 24% respectively) in comparison to the uterotonic pattern of γ-irradiation alone. The results indicate a promising tocolytic activity of Diltiazem against the uterotonic effect of γ-radiation.

Fetal heart rate and uterine contractility during maternal exercise at term

OBJECTIVE: Our aim was to assess the physiologic response of human fetal heart rate and uterine contractility to moderately strenuous maternal exercise. STUDY DESIGN: We measured fetal heart rate and intrauterine pressure with the use of internal monitoring before, during, and after maternal exercise at a heart rate of 140 beats/min on a cycle ergometer in 30 term women admitted for elective induction of labor. The fetal heart rate tracings were assessed by three observers and were classified according to Fischer et al. and Nijhuis et al., and the frequency and intensity of uterine contractions were determined. RESULTS: Fetal outcome was good in all cases. There were no significant differences in Fischer scores between rest, exercise, and recovery periods. The fetuses displayed a heart rate pattern A and B, indicative of behavioral states 1F or 2F, 85% of the time, with state changes apparently independent of exercise. Uterine activity increased significantly during the exercise period, with a 5.5-fold increase in contraction frequency and a fourfold increase in time-pressure integral compared with rest, with rapid recovery after the exercise. CONCLUSION: Exercise in healthy pregnant women at term does not cause a change in fetal heart rate pattern suggestive of fetal distress or a change in fetal behavioral pattern, but it does significantly increase uterine activity. (A M J O BSTET G YNECOL 1996;174:43-8.)

Phasic maternal prolactin secretion during spontaneous labor is associated with cervical dilatation and second-stage uterine activity

In this study, we attempted to determine the physiologic roles of prolactin (PRL) and hCG during labor. Serial blood samples were collected from 19 women (15 multiparous and four nulliparous) before, during, and after labor; assayed for PRL and hCG; and compared with cervical dilatation and uterine contraction frequency. Prolactin levels decreased in association with progressive cervical dilatation during the first stage of labor and reached a nadir at full dilatation. Thereafter, PRL increased rapidly during the second stage of labor and peaked within 1 hour postpartum. Uterine contraction frequency also increased during the second stage and correlated significantly (r2 = 0.60; P = .0006) with levels of PRL. Levels of hCG increased during labor and peaked at about the time of delivery. These data suggest that phasic PRL secretion is associated with cervical dilatation and that after transition to the second stage of labor, uterine contraction frequency may be associated with the increase in PRL levels.

Myometrium of the spiny dogfish Squalus acanthias: peptide and steroid regulation

The phylogenetic age of endocrine control of viviparous reproduction in vertebrates may be estimated by examination of elasmobranch models. We have shown in pregnant Squalus acanthias that Squalus relaxin (sRLX) significantly decreased the frequency of myometrial contractions in a dose-dependent reversible manner in vitro and in vivo, without altering the intensity or duration of contractions. In contrast, neurointermediate lobe extract provoked a marked and reversible enhancement of the duration and intensity of contractions but was ineffective in altering the frequency of contractions. In steroid-primed animals, untreated and estradiol-17 beta (E2)-treated animals exhibited a decrease in the frequency of activity after injection of sRLX in vivo while pretreatment with progesterone (P4) alone or in combination with E2 fully suppressed the effects of sRLX. These results suggest that homologous sRLX slows the frequency of spontaneous uterine contractions in third-trimester sharks (stage C) in which endogenous P4 is reduced and E2 levels are rising. These data demonstrate the physiological importance of these hormones and the antiquity of reproductive tract control mechanisms.

Fetal fibronectin improves the accuracy of diagnosis of preterm labor

OBJECTIVE: Our purpose was to assess the utility of cervicovaginal expression of fetal fibronectin in the diagnosis of preterm labor. STUDY DESIGN: Women seen between 24 and 34 weeks' gestation with symptoms of preterm labor, intact membranes, and cervical dilatation <3 cm were enrolled at five university medical centers. Cervicovaginal swabs were obtained and assayed for the presence of fetal fibronectin by means of a monoclonal antibody assay. Results were compared with cervical dilatation and uterine contraction frequency as indicators of interval to delivery and delivery before 37 weeks. RESULTS: A total of 192 eligible women at a mean gestational age of 30.8 ± 2.9 weeks were enrolled from a population of 418 subjects screened. The rate of preterm birth was 32.3% ( 62 192 ). The mean interval from presentation to delivery was 25.3 ± 24.1 days in the 45 subjects with a positive fibronectin assay and 52.4 ± 24.8 days in the 147 subjects with a negative assay ( p = 0.0001). The sensitivity, specificity, and positive and negative predictive values of fetal fibronectin expression for delivery <37 weeks were 44% ( 27 62 ), 86% ( 112 130 ), 60% ( 27 45 ), and 76% ( 112 147 ). The fetal fibronectin assay was especially useful in predicting risk of delivery within 7 days (sensitivity 93% [ 13 14 ], specificity 82% [ 146 178 ], positive predictive value 29% [ 13 45 ], and negative predictive value 99% [ 146 147 ]) and was notably superior to both cervical dilatation >1 cm and contraction frequency greater than or equal to eight per hour (sensitivities 29% and 42%, specificities 82% and 67%, positive predictive values 11% and 9%, and negative predictive values 94% and 94%, respectively). CONCLUSION: Cervicovaginal fetal fibronectin predicts delivery within 7 days more accurately than do cervical dilatation and contraction frequency in a population of women evaluated for early preterm labor.

Oral administration of methylergometrine shows a late and unpredictable effect on the non-pregnant human menstruating uterus

Objective: To study the pharmacodynamic and pharmacokinetic properties of oral and intravenous methylergometrine upon uterine motility during menstruation. Study-design: Intra-uterine pressure was measured in six volunteers with a fluid-filled sponge-tipped catheter during menstruation. Methylergometrine was given orally (0.5 mg) or intravenously (0.2 mg) in a cross-over design. Results: After intravenous administration, a fast increase of the frequency of uterine contractions and basal tone occurred with a decrease of amplitude, lasting at least 30 min. Oral administration had a late and less marked effect on uterine motility. An intravenous dose administered 24 h after an oral dose had no effect on uterine motility. Pharmacokinetic data, such as the maximum plasma concentration ( C max ), the time at which C max is reached ( t max ) and the half-life of absorption ( t 1 2abs ) also demonstrated large individual variations after oral administration. Conclusion: Oral administration of methylergometrine had an unpredictable and late effect on uterine motility on the menstruating uterus, probably due to an unpredictable bioavailability, in contrast with the fast and predictable effect after intravenous administration.

Effect of nuchal cord on fetal cerebral haemodynamics and oxygenation measured by near infrared spectroscopy during labour

Objective: To test the hypothesis that a nuchal cord has a significant effect upon fetal cerebral haemodynamics and oxygenation during labour. Study design: A specially designed optical probe was inserted through the dilated cervix and placed against the scalp of 37 fetuses during labour in a teaching hospital obstetric unit. Changes in total cerebral haemoglobin concentration were measured continuously together with fetal heart rate and uterine contraction frequency during the first and second stages. At birth 11 fetuses (30%) were noted to have a nuchal cord (cord around the neck). For these, significantly more contractions were associated with an increase in total cerebral haemoglobin concentration when compared with the control fetuses without a nuchal cord (40.2% (S.D.19.5) vs 5.9% (S.D.7.1), P < 0.001). A significantly greater number of variable decelerations was found in the nuchal cord group (4 per 30 min vs. 2 per 30 min in the controls) ( P < 0.01). There was no significant difference between mean cerebral oxygen saturation determined at the end of the first stage of labour, which was 47.0% (S.D.13.3) and 50.1% (S.D.11.8) for the nuchal cord and control groups, respectively. A nuchal cord was associated with a significant increase in cerebral blood volume during uterine contractions, without any significant effect upon cerebral oxygenation.

The effects of thyroidectomy and thyroxine on the reactivity of rat uterine muscle to electrical stimulation in vitro

The effects of thyroidectomy and thyroxine on the reactivity of rat uterine muscle to electrical stimulation in vitro was studied in adult albino Wistar-strain rats. Thyroidectomy decreased the frequency of uterine smooth-muscle contraction. Thydroidectomy 6–8 μg/100 g body wt. per day) for 35 days caused a potentiation of acetylcholine and ergometrin-induced contractile responses of the uterine smooth muscle. This findings suggest that the thyroid hormone affects the intrinsic contractile state of the uterine smooth muscle.