Time Of Elective Cesarean Section Research Articles

The Role of Parathyroid Hormone-Related Protein in Intra-Tracheal Fluid.

Parathyroid hormone-related protein (PTHrP), a multi-functional protein, is produced by many tissues in fetus. PTHrP concentration in amniotic fluid is reported to be significantly higher than in either fetal or maternal plasma. Other investigators have reported that PTHrP in amniotic fluid is derived mainly from amnion. The aim of this study was to investigate the contribution of fetus to PTHrP in amniotic fluid and the role of PTHrP in human fetal lung tissue. Samples of amniotic fluid, neonatal intra-tracheal fluid, gastric fluid, and the first urine of neonates were obtained at the time of elective cesarean section (n=11), and the concentrations of PTHrP were measured. The PTHrP level in intra-tracheal fluid (41.0+/-19.6 pmol/l, mean+/-SD) was significantly higher than the levels in amniotic fluid (22.1+/-0.8), neonatal gastric fluid (13.5+/-2.5), first urine (0.95+/-0.6), umbilical cord venous and arterial plasma (1.35+/-0.2, 1.63+/-0.3) and maternal plasma (1.05+/-0.1). PTHrP and PTH/PTHrP receptor mRNA were detected in human lung tissue obtained from a fetus stillborn at 36 weeks of gestation. The effects of PTHrP on fetal lung maturation were studied in H441 cells from a human lung epithelial cell line. PTHrP (10(-7)M) significantly suppressed cell proliferation (p<0.05) to approximately 80% of the control level, while administration of PTHrP significantly increased surfactant protein A production (p<0.01). We first demonstrated the high concentration of PTHrP in intra-tracheal fluid that may suggest the positive production of this protein from the fetal lung. The results obtained by in vitro study using a human lung epithelial cell line suggest that PTHrP derived from the fetal lung might modulate its own maturation.

Differential release of interleukin-6 from human gestational tissues in association with labour and in vitro endotoxin treatment.

In this study, we quantified interleukin-6 (IL-6) concentrations in amniotic fluid at term and preterm labour, and determined the gestational tissue source of IL-6. In addition, aspects of the regulatory mechanisms involved in IL-6 release at the time of term labour and in response to bacterial endotoxin, lipopolysaccharide (LPS), have been established. IL-6 concentrations were 2-fold higher in amniotic fluid collected at term compared with preterm gestation, with an additional 2-fold increase in association with term labour. IL-6 was released from all choriodecidual and placental explants but was detected in only 33% of amniotic explant cultures of tissues obtained before labour onset. In contrast, IL-6 was detected in all amniotic, choriodecidual and placental cultures of tissues obtained after term labour onset and delivery, and the mean IL-6 release was significantly higher than that measured in explant cultures of both amniotic (80-fold increase, P < 0.0001) and choriodecidual (3-fold increase, P < 0.02) but not placental explants taken at the time of elective Caesarean section at term before labour onset. LPS significantly (P < 0.05) increased the release of IL-6 from human choriodecidual and placental explants but not amniotic explants, in a time- and dose-dependent manner. IL-6 is a physiological constituent of amniotic fluid and its production by gestational tissues is differentially regulated by LPS and spontaneous labour onset and delivery.

A study of monoamine oxidase activity in fetal membranes.

To study the role of decidual monoamine oxidase (MAO)-A and -B activities before delivery, the relationship between MAO activity in fetal membranes and catecholamine (CA) concentration in amniotic fluid (AF) was determined. Fetal membranes and AF were obtained at the time of elective Cesarean section (CS group, n = 11) and Cesarean section due to fetal distress without labor pains (FD group, n = 5). MAO-A and -B activities were radiometrically measured using 14C-5-hydroxytriptamine for MAO-A substrate and 14C-benzylamine for MAO-B substrate. CA concentrations in AF were measured by high performance liquid chromatograph with an electro-chemical detector. Both MAO-A and -B activities in decidua obtained from CS were significantly lower than those obtained from FD. Both norepinephrine (NE) and epinephrine (EP) concentrations were significantly lower in the CS group than the FD group. A significant positive correlation between decidual MAO-A activity and NE concentration in AF was observed. No significant correlation was observed between MAO-B activity and the concentration of NE in AF. There was no correlation between EP concentrations and MAO activities. These results suggest that CA concentration in AF may be related to the activity of MAO in fetal membranes, determined by certain physiological processes during pregnancy. It has been suggested that metabolism of monoamines in fetal membranes also plays an important role in reducing monoamine influx into maternal myometrium from the AF.

Lack of evidence for a circadian rhythm of IGFBP‐1 in the mother and fetus during labour

To determine whether the circadian rhythm of circulating levels of insulin-like growth factor binding protein-1 (IGFBP-1) is evident at the time of delivery. Prospective observational study in six pregnant women and cross-sectional study in 65 women at the time of delivery. Six pregnant women sampled over a period of 24 hours, 23 women sampled at the time of elective caesarean section, and 42 women sampled at the time of vaginal delivery. In the women sampled serially over a 24 hour period there was an obvious circadian rhythm of IGFBP-1 with a peak between 01.00 and 09.00 hours. In the women sampled at the time of delivery there was no evidence for any relationship between the time of delivery and maternal or fetal levels of IGFBP-1. The circadian rhythm of IGFBP-1 is not observed in women in labour. Therefore, the time of day is not an important confounding variable in studies on IGFBP-1 levels at the time of normal delivery.

Neonatal respiratory morbidity and mode of delivery at term: influence of timing of elective caesarean section

Neonatal respiratory morbidity and mode of delivery at term: influence of timing of elective caesarean section

Neonatal respiratory morbidity and mode of delivery at term: influence of timing of elective caesarean section

To establish whether the timing of delivery between 37 and 42 weeks gestation influences neonatal respiratory outcome and thus provide information which can be used to aid planning of elective delivery at term. All cases of respiratory distress syndrome or transient tachypnoea at term requiring admission to the neonatal intensive care unit were recorded prospectively for nine years. Rosie Maternity Hospital, Cambridge. During this time 33,289 deliveries occurred at or after 37 weeks of gestation. This information enabled calculation of the relative risk of respiratory morbidity for respiratory distress syndrome or transient tachypnoea in relation to mode of delivery and onset of parturition for each week of gestation at term. The incidence of respiratory distress syndrome at term was 2.2/1000 deliveries (95% CI; 1.7-2.7). The incidence of transient tachypnoea was 5.7/1000 deliveries (95% CI; 4.9-6.5). The incidence of respiratory morbidity was significantly higher for the group delivered by caesarean section before the onset of labour (35.5/1000) compared with caesarean section during labour (12.2/1000) (odds ratio, 2.9; 95% CI 1.9-4.4; P < 0.001), and compared with vaginal delivery (5.3/1000) (odds ratio, 6.8; 95% CI 5.2-8.9; P < 0.001). The relative risk of neonatal respiratory morbidity for delivery by caesarean section before the onset of labour during the week 37+0 to 37+6 compared with the week 38+0 to 38+6 was 1.74 (95% CI 1.1-2.8; P < 0.02) and during the week 38+0 to 38+6 compared with the week 39+0 to 39+6 was 2.4 (95% CI 1.2-4.8; P < 0.02). A significant reduction in neonatal respiratory morbidity would be obtained if elective caesarean section was performed in the week 39+0 to 39+6 of pregnancy.

Lactate Metabolism in Normal and Growth-Retarded Human Fetuses

Lactate concentration and oxygen content were measured in 21 normal (AGA) and 34 intrauterine growth-retarded (IUGR) infants at the time of elective cesarean section. Maternal lactate and umbilical arterial and venous lactate concentrations were significantly higher in IUGR infants compared with AGA infants. However, when IUGR patients were subdivided according to pulsatility index (PI) measurements of the umbilical artery, no differences were detected between AGA and IUGR patients with PI less than 4 SD, whereas IUGR patients with PI greater than 4 SD had higher lactate concentrations in maternal arterial blood and umbilical arterial and venous blood from both other groups. There was a significant inverse linear relationship between umbilical arterial lactate concentration and umbilical venoarterial differences for both lactate concentrations and for lactate/oxygen quotients. These relationships were significantly different in IUGR fetuses with PI greater than 4 SD compared with AGA and IUGR fetuses with PI less than 4 SD. AGA and IUGR fetuses with PI less than 4 SD have arterial lactate concentrations less than 2 mM even at low oxygen concentrations (O2 content less than 2 mM, O2 saturations less than 20%). At comparable levels of oxygenation, IUGR fetuses with PI greater than 4 SD have a marked lactacidemia. The data suggest that coupling Doppler assessment of flow velocimetry with biochemical analyses of fetal blood can be useful in identifying a subset of IUGR human fetuses at risk of intrauterine hypoxia.

Plasma and amniotic fluid immunoreactive neuropeptide-Y level changes during pregnancy, labor, and at parturition.

This study was designed to determine the presence of and possible changes in plasma and amniotic fluid immunoreactive neuropeptide-Y (irNPY) levels in pregnant women during gestation and at parturition. We studied 127 healthy pregnant and 12 nonpregnant women. The peptide was extracted from plasma or amniotic fluid with a propanolformic acid mixture and measured by RIA. The mean plasma irNPY concentration in 15 pregnant women during the first trimester of gestation was 129 +/- 12 (+/- SE) pmol/L, compared to 40 +/- 8 pmol/L in nonpregnant women (p less than 0.01). The mean values were 144 +/- 13 and 156 +/- 24 pmol/L, respectively, in 15 pregnant women during the second trimester and 33 women during the third trimester. These values did not differ from that during the first trimester. Amniotic fluid irNPY levels were similar to those in plasma and did not vary among the 3 groups of women studied during the various trimesters of gestation. During labor, plasma irNPY levels progressively increased, reaching the highest levels at the most advanced stages of cervical dilatation (greater than 8 cm, 351 +/- 38 pmol/L) and at the time of vaginal delivery (416 +/- 73 pmol/L). Plasma irNPY levels then decreased significantly 2 h after vaginal delivery. The amniotic fluid irNPY levels in women during the early or late stages of labor were similar. Moreover, plasma and amniotic fluid irNPY levels at the time of elective cesarean section also were similar. These results indicate that pregnant women have high plasma and amniotic fluid irNPY levels and that the stress of labor results in a further increase in plasma levels, suggesting a possible role of NPY in human pregnancy and parturition.

Failure of endotoxin to cross the chorioamniotic membranes in vitro.

We have previously reported the detection of endotoxin in the amniotic fluid of patients with gram-negative intra-amniotic infection. Endotoxin or lipopolysaccharide (LPS) is a potent biologic product capable of inducing prostaglandin release from several cell types, and therefore may be involved in the onset of human parturition in the setting of intra-amniotic infection. The experiments outlined in this report were designed to determine whether endotoxin crosses chorioamniotic membranes in vitro. Chorioamniotic membranes obtained at the time of elective cesarean section were placed in Ussing chambers used for transport experiments. Endotoxin was placed in one chamber, and serial timed samples were taken from both chambers for endotoxin quantification, which was performed with the limulus amebocyte gel clot assay. Blue dextran was used to exclude the presence of large defects. Bromophenol blue was used to demonstrate membrane permeability to low-molecular weight substances. Endotoxin failed to cross the chorioamniotic membranes in all experiments (n = 11).

Correlation between function of the pituitary-thyroid axis and metabolism of catecholamines by the fetus at delivery.

The relationship between the pituitary-thyroid axis and the metabolism of catecholamines has been studied in 33 maternal, arterial and venous cord blood specimens obtained at the time of normal vaginal delivery, following uncomplicated pregnancies. Ten fetal cord blood samples were collected at the time of elective caesarean section. Levels of noradrenaline and 3,4-dihydroxyphenylacetic acid (DOPAC) were measured in all these samples, using the high performance liquid chromatography (HPLC)-electrochemical detection method, and TSH was measured by radioimmunoassay. In cord arterial blood samples at vaginal delivery the levels of plasma noradrenaline and serum TSH were significantly increased, but those of DOPAC, which reflects central dopaminergic activity, were unchanged when compared to samples obtained at elective caesarean section. Within the same samples there was a significant correlation between the levels of plasma noradrenaline and those of serum TSH. Noradrenaline is believed to have a stimulatory and dopamine an inhibitory influence on TSH secretion. The fetal thyroid gland seems to respond adequately to the stimulus of TSH at term. The present study suggests that catecholamines, especially noradrenaline, may regulate secretion of TSH from the pituitary gland in the fetus at delivery and that elevation of TSH probably induces a subsequent rapid increase in thyroid hormones in the neonate.

Respiratory Gases, Acid-Base Balance and Lactate Concentrations of the Midterm Human Fetus

Respiratory gases, acid-base balance, and lactate and hemoglobin concentrations were measured in 14 fetal blood samples between 17 and 21 weeks of gestation. The samples were obtained at the time of fetoscopy performed for prenatal diagnosis. Results have been compared with two reference groups: (a) 4 patients in whom fetal cord blood sampling was performed at 32-36 weeks of gestation, and (b) 10 patients at the time of elective cesarean section, 35-39 weeks. PO2 and oxygen saturations were significantly higher and hemoglobin concentration lower in the mid-gestation fetus. Acid-base balance was not significantly different. There was a significant correlation between maternal and fetal hemoglobin concentrations. The oxygen affinity of fetal blood was not significantly different from that described for term fetuses with a oxygen saturation of less than 90%.

Transplacental arteriovenous gradients for glucose, insulin, glucagon and placental lactogen during normoglycaemia in human pregnancy at term

The potential contributions of placental extraction and degradation to glucoregulatory hormone turnover in late pregnancy were assessed by measuring arteriovenous differences for glucose, insulin, glucagon and human placental lactogen (hPL) across the uterine and fetal circulation in ten pregnant women at the time of elective caesarean section. The observations were made during stable conditions of euglycaemia; values for maternal arterial glucose, insulin, glucagon and hPL were 78.8 +/- 5.0 mg/dl, 10.1 +/- 2.1 microU/ml, 72.0 +/- 8.5 pg/ml and 5.18 +/- 0.59 micrograms/ml, respectively. The glucose decrements observed consistently across the uterus and fetus indicated uptake by the placenta and fetus, and in the maternal circulation the arterial-uterine vein increment for hPL was 2.10 +/- 0.44 micrograms/ml. However, within the limits of analytical accuracy, no significant gradient could be demonstrated for insulin across the uterine (maternal) or umbilical (fetal) circulations. A small (8.5 per cent) but significant arteriovenous difference for glucagon was observed across the uterus but none was found on the fetal side of the placenta. The findings indicate that detectable gradients for insulin cannot be demonstrated under basal conditions of metabolism and at normal rates of placental blood flow. The results do not exclude the possibility of more significant extraction ratios under other physiological conditions or at higher concentrations of glucoregulatory hormones.

Arginine Vasopressin in Amniotic Fluid, Arterial and Venous Cord Plasma and Maternal Venous Plasma

High concentrations of arginine vasopressin (AVP) in arterial umbilical cord blood at the time of delivery have been attributed to either a generalized increase in the activity of the fetal endocrine system at the onset of labor or to fetal asphyxia. We measured AVP in amniotic fluid, arterial and venous cord blood and in maternal venous blood from 13 patients at 38-40 weeks of gestation at the time of elective cesarean section with a nonasphyxic fetus (group I), in amniotic fluid from 19 patients at 15-17 weeks of gestation (group II) and in venous blood from 13 nonpregnant control subjects (group III). Our results showed a high concentration of AVP in the amniotic fluid both in the middle and at the end of normal pregnancy and at the same level as in arterial cord blood, whereas AVP in the venous cord blood was significantly lower and at the same level as in the maternal venous blood and in the control group. It is concluded that the fetus produces AVP and this is at least not solely caused by fetal asphyxia or related to parturition.

Prolonged inhibition of human myometrial contractility by intermittent isoproterenol

Regular, spontaneous contractions of human myometrial strips obtained at the time of elective cesarean section were recorded in a tissue bath in five experiments. Administration of the β-adrenergic agonist isoproterenol (1 μmol/L) resulted in the rapid onset of myometrial relaxation. In the continuous presence of the β-agonist, myometrial contractions of amplitude equal to or greater than that of baseline resumed after 10 to 40 minutes (mean ± SEM = 29.7 ± 7.3), indicating the development of desensitization of the tissue to the tocolytic effects of isoproterenol. In contrast, intermittent exposure of the myometrial strips to isoproterenol prevented the onset of desensitization and resulted in prolonged inhibition of myometrial contractions. These findings suggest that modification of the present regimen of administration of β-adrenergic agonists from continuous to intermittent infusion may improve the success of these agents in the prevention of preterm births.

EQUINE HERPESVIRUSES: Experimental Infecton of a Foetus with Type 2

SummaryIntrauterine infection of pregnant mare with equine herpesvirus type 2 (EHV 2) did not result in foetal abortion, stillbirth or recognisable disease. Collection of uterine fluid by allantocentesis or amniocentesis 107 days after inoculation confirmed that intrauterine infection was established. EHV 2 was isolated from both allantoic and amniotic fluid separately collected at the time of elective Caesarean section 156 days after inoculation and virus neutralising antibody to EHV 2 was present in the foal's presuckle serum at birth. A very mild clinical disease, characterised by a scant, mucous oculo‐nasal discharge was observed between 4 and 11 days after birth. EHV 2 was isolated from 22 nasal swabs taken between birth and 65 days of age, on which day the foal was infected with equine adenovirus. EHV 2 was not isolated from 6 nasal swabs collected from 66 to 71 days of age.

The phospholipid test of fetal respiratory maturity: its value in clinical obstetrics.

Summary: The lecithin‐sphingomyelin ratio has been studied in amniotic fluid samples from 122 patients. The respiratory distress syndrome developed in 11 of the babies. The importance of a transitional zone in which respiratory function in the newborn cannot be predicted with certainty is stressed. We have found the test to be of much value in deciding the timing of elective Caesarean section or induction of labour.

The transplacental passage of prednisone and prednisolone in pregnancy near term

The transplacental passage of prednisone and prednisolone was studied in late pregnancy during a constant infusion of the radioactive steroids to mothers at the time of elective cesarean section. The metabolic clearance rates, conversion ratios, and transfer constants of prednisone and prednisolone of the mothers were compared with those of normal women and women receiving contraceptives. It was found that irrespective of whether 3 H-prednisone or 3 H-prednisolone was infused, the concentration of 3 H-prednisolone in the maternal plasma was significantly higher than that of 3 H-prednisone. The maternal 3 H-prednisone concentration was similar to the fetal 3 H-prednisone concentration. The fetal 3 H-prednisone concentration was not significantly different from the fetal 3 H-prednisolone concentration which was, however, about 8-to 10-fold less than the maternal 3 H-prednisolone concentration. Pregnancy and contraceptive-medication had no effect on the metabolic clearance rates of prednisone or the conversion ratio of prednisone to prednisolone. The metabolic clearance rate of prednisolone was significantly lower than that of prednisone in both pregnant and nonpregnant women.

Placental Passage and Fetal Secretion of Aldosterone

The transplacental passage and production of aldosterone by the mother and fetus were studied near term during a constant infusion of 1,2-3H-aldosterone to 9 mothers at the time of elective cesarean section. This study showed that there was a transplacental passage of aldosterone. The fetal plasma levels of 1,2-3H-aldosterone, expressed as percentage of the matternal values, ranged from 40.0 to 79.2%. The levels of non-labeled hormone, determined by a double isotope dilution technique, were consistently higher in the fetus than in the mother (mean±SD = 17.2±9.5 mμg/100 ml and 3.7±1.4 mμg/100 ml, respectively). Since the specific activities of aldosterone were lower in the fetus than in the mother (6.5 to 23.4%), and if one assumes that equilibrium between maternal and fetal compartments was reached after more than 2 h of constant infusion, it can be concluded that the fetus secretes aldosterone. The metabolic clearance: ate of aldosterone was not modified by pregnancy. The steroid blood production of the mothers was about twice the non-pregnant values. the relatively small increments might be related to the fact that our subjects were supine for at least 10 h at the time of the study.

Transplacental passage and fetal secretion of aldosterone.

The transplacental passage and the production of aldosterone were studied in late pregnancy during a constant infusion of 1,2-aldosterone-(3)H to mothers at the time of elective cesarean section. It was found that, while maternal aldosterone crossed the placenta, there was a significant secretion of aldosterone by the fetus. The aldosterone concentration in fetal plasma was 2-12 times higher than that of the corresponding mothers. Pregnancy had no effect on the metabolic clearance rate of aldosterone, but it increased the rate of production of this steroid. However, the increments that we observed were smaller than those reported in previous reports. The discrepancy was probably due to differences in body posture, our subjects being supine for at least 10 hr at the time of study.

Further observations on the relationships of pyruvate and lactate in human pregnancy

The present study is designed to evaluate adequacy of oxygen supply relative to metabolic needs. Estimates of excess lactate production were done in the human pregnant mother and fetus at the time of elective cesarean section. The evidence from the observations noted suggests that the pregnant uterus as a whole is not forced to resort to anaerobic tissue metabolism by the degrees of maternal hypoxemia studied except in rare instances.