Corticosteroids and fetal vasculature: effects of hydrocortisone, dexamethasone and betamethasone on human umbilical artery

Clinical significance of umbilical artery intermittent versus persistent absent end-diastolic velocity in growth-restricted fetuses

BACKGROUND

Umbilical artery absent end-diastolic velocity (AEDV) indicates increased placental resistance and is associated with increased risk of perinatal demise and neonatal morbidity in fetal growth restriction (FGR). However, the clinical implications of intermittent (iAEDV) versus persistent (pAEDV) absent end-diastolic velocity are unclear.

OBJECTIVE

We compared umbilical artery Doppler (UAD) velocimetry changes during pregnancy and neonatal outcomes in pregnancies with FGR and iAEDV versus pAEDV.

STUDY DESIGN

In this retrospective study of singletons with FGR and AEDV, UAD abnormalities were classified as follows: iAEDV (< 50% cardiac cycles with AEDV) and pAEDV (≥ 50% cardiac cycles AEDV). The primary outcome was UAD progression to reversed end-diastolic velocity (REDV). Secondary outcomes included sustained UAD improvement, latency to delivery, gestational age (GA) at delivery, neonatal morbidity composite, rates of NICU admission, and length of NICU stay. Outcomes were compared between iAEDV and pAEDV. Multivariate logistic regression was used to adjust for confounders. A receiver operative characteristic curve was generated to assess the sensitivity and specificity of the percentage of waveforms with AEDV in predicting the neonatal composite. The Youden's index was used to calculate the optimal cut-point for percentage of waveforms with AEDV to predict the neonatal composite.

RESULTS

Of the 77 patients included, 38 had iAEDV and 39 had pAEDV. Maternal characteristics, including age, parity, and pre-existing conditions did not differ significantly between the two groups. Progression to REDV was less common in iAEDV vs pAEDV (7.9% vs 25.6%, OR 0.25, 95% CI 0.06-0.99). Sustained UAD improvement was more common in iAEDV vs pAEDV (50.0% vs 10.3%; OR 8.75, 95% CI 2.60-29.5). Pregnancies with iAEDV had longer latency to delivery compared to those with pAEDV (11 vs 3 days, p<0.01), and later GA at delivery (33.9 vs 28.7 weeks, p<0.01). Composite neonatal morbidity was less common in the iAEDV group (55.3% vs 92.3%, p<0.01). Neonatal death occurred in 7.9% of iAEDV cases and 33.3% of pAEDV cases (p<0.01). The differences in neonatal outcomes were no longer significant when controlling for GA at delivery. The percentage of cardiac cycles with AEDV is a modest predictor for neonatal morbidity with an AUC of 0.71 (95% CI 0.58-0.84). The optimal cut-point of percent fetal cardiac cycles with AEDV seen at the sentinel ultrasound for predicting neonatal morbidity was calculated to be 47.7%, with a sensitivity of 65% and specificity of 85%.

CONCLUSIONS

Compared to pAEDV, diagnosis of iAEDV in the setting of FGR is associated with lower rates of progression to REDV, higher likelihood of UAD improvement, longer latency to delivery, and later GA at delivery, leading to lower rates of neonatal morbidity and death. Our data support utilizing a cut-point of AEDV in 50% of cardiac cycles to differentiate iAEDV versus pAEDV. This differentiation in growth-restricted fetuses with AEDV may allow further risk stratification.

Perinatal outcome after persistence of abnormal umbilical artery Doppler indices in the growth-restricted fetus following betamethasone administration

BACKGROUND

An optimal approach for providing sufficient antenatal surveillance for fetal growth restriction (FGR) has yet to be elucidated. Moreover, there is scant literature on the fetal response to betamethasone and its effect on fetal Dopplers.

OBJECTIVE

To compare persistence of umbilical artery Doppler abnormalities after corticosteroid administration and adverse perinatal outcome in growth restricted fetuses.

METHODS

Retrospective cohort study (2008-2018) of singleton gestations with FGR (EFW <10th percentile) and umbilical artery Doppler abnormalities (absent or reversed end diastolic velocity) between 24 and 34 weeks of gestation at two institutions. Included patients had Dopplers performed before betamethasone administration and again within 1 week. Excluded were multiple gestations, chromosomal abnormalities, fetal anomalies, or missing outcome information. Pregnancies with persistently abnormal Dopplers were compared with those in which an improvement of Dopplers was noted. The primary outcome was a composite that consisted of indicated preterm birth <32 weeks, 1 or 5 min APGAR score <7, intrauterine fetal demise, and neonatal demise. Secondary outcomes included length of NICU stay, ventilator support, gestational age at delivery, interval between steroids and delivery, and birth weight.

RESULTS

Fifty-three FGR pregnancies met inclusion criteria. Umbilical artery Dopplers improved after steroids in 32% (n = 17). No difference in the frequency of the primary outcome was observed between the persistently abnormal Doppler and improved Doppler groups (72.2% vs. 70.6%, respectively), and there was no difference in any of the secondary outcomes.

CONCLUSIONS

Perinatal outcomes in FGR pregnancies were not affected by improved versus persistently abnormal umbilical artery Dopplers after betamethasone administration.

Improvement of cardiac function in fetuses with growth restriction following antenatal betamethasone administration: fact or artifact?

INTRODUCTION

Use of corticosteroids for fetal lung maturation has reduced the perinatal mortality/morbidity from prematurity related complications. There is a paucity of studies evaluating the effect of steroid administration on the fetal circulation and cardiac function in fetal growth restriction (FGR). The aim of the study was to assess changes in fetal Doppler indices and cardiovascular function in pregnancies complicated with FGR after administration of betamethasone.

METHODS

This was a prospective study conducted in a tertiary care research center between July 2017 and May 2018. Pregnant women with FGR between 28 and 36 weeks' gestation, who were scheduled to receive betamethasone (two doses of 12 mg, 24 h apart) were recruited. Fetal cardiovascular function in fetuses FGR was assessed immediately before first dose and once between 6 and 24 h after the second dose of betamethasone by the same operator. Wilcoxon matched-pairs signed-rank test or paired t-tests were used to compare parameters before and after corticosteroid exposure.

RESULTS

Fifty cases with FGR were evaluated before and after administration of betamethasone, at mean gestational age of 34.6 ± 2.0 weeks. Fetal heart rate (148.78 ± 9.10 versus 144.73 ± 9.61, p < .001), left heart myocardial performance index ([MPI], 0.66 ± 0.06 versus 0.55 ± 0.09, p ≤ .001) and right heart MPI (0.65 ± 0.04 versus 0.63 ± 0.04, p .016) showed improvement after steroids. Left heart isovolumic relaxation and contraction indices along with ejection time of both sides showed a small but statistically significant improvement (p < .001), but other fetal cardiac functional and Doppler indices remain unchanged after steroids.

CONCLUSIONS

Fetal heart rate, cardiac MPI, left sided isovolumic indices showed an improvement after betamethasone administration. Follow up studies are needed to ascertain whether these effects persist in the long term and to determine whether these are beneficial to a growth restricted fetuses.

Excess Hydrocortisone Hampers Placental Nutrient Uptake Disrupting Cellular Metabolism

Low birth weight increases neonatal morbidity and mortality, and surviving infants have increased risk of metabolic and cardiovascular disturbances later in life, as well as other neurological, psychiatric, and immune complications. A gestational excess of glucocorticoids (GCs) is a well-known cause for fetal growth retardation, but the biological basis for this association remains elusive. Placental growth is closely related to fetal growth. The placenta is the main regulator of nutrient transport to the fetus, resulting from the difference between placental nutrient uptake and the placenta's own metabolism. The aim of this study was to analyze how excess hydrocortisone affects placental glucose and lipid metabolism. Human placenta explants from term physiological pregnancies were cultured for 18 hours under different hydrocortisone concentrations (2.75, 5.5, and 55 mM; 1, 2, and 20 mg/ml). Placental glucose and lipid uptake and the metabolic partitioning of fatty acids were quantified by isotopic techniques, and expression of specific glucose transporter GLUT1 was quantified by western blot. Cell viability was assessed by MTT, immunohistochemistry and caspase activity. We found that excess hydrocortisone impairs glucose uptake and lipoprotein lipase (LPL) activity, coincident with a GC-dose dependent inhibition of fatty acid oxidation and esterification. None of the experimental conditions showed an increased cell death. In conclusion, our results show that GC overexposure exerts a dysfunctional effect on lipid transport and metabolism and glucose uptake in human placental explants. These findings could well be directly related to a reduced placental growth and possibly to a reduced supply of nutrients to the fetus and the consequent fetal growth retardation and metabolic programming.

Clinical implications of umbilical artery Doppler changes after betamethasone administration†

Background: Betamethasone (BMZ) is commonly administered to patients with fetal growth restriction (FGR) and abnormal umbilical artery Doppler (UAD) velocimetry due to the increased risk of preterm delivery; however, the clinical impact of UAD changes after BMZ exposure is unknown.Objective: To test the hypothesis that lack of UAD improvement after BMZ administration is associated with shorter latency and greater neonatal morbidity in patients with FGR.Study design: This was a retrospective cohort study of pregnancies complicated by FGR and abnormal UAD between 24⁰ and 33⁶ weeks gestation. Abnormal UAD included the following categories of increasing severity: elevated (pulsatility index >95%), absent end diastolic flow (EDF), or reversed EDF improvement was defined as any improvement in category of UAD within two weeks of BMZ. Sustained improvement was defined as improvement until the last ultrasound before delivery, whereas transient improvement was considered as unsustained. The primary outcome was latency, defined as interval from betamethasone administration to delivery. Secondary outcomes were gestational age at delivery, umbilical artery pH, and a composite of neonatal morbidity (intubation, necrotizing enterocolitis, ionotropic support, intraventricular hemorrhage, total parenteral nutrition, neonatal death). Outcomes were compared between (a) patients with and without UAD improvement and (b) patients with sustained and unsustained improvement, using univariable, multivariable and time-to-event analyses.Results: Of the 222 FGR pregnancies with abnormal UAD, 94 received BMZ and had follow-up ultrasounds. UAD improved in 48 (51.1%), with 27 (56.3%) having sustained improvement. Patients with hypertension and drug use were less likely to have UAD improvement. Patients without UAD improvement had shorter latency (21.5 days [interquartile range (IQR) 8,45] versus 35 [IQR 22,61], p = .02) and delivered at an earlier gestational age (34 weeks [IQR 31,36] versus 37 [IQR 33,37], p < .01) than those with improvement. There were no differences in umbilical artery pH between groups. Composite neonatal morbidity was higher in patients without UAD improvement, but this was not statistically significant after adjusting for confounders (aOR 2.0; 95% CI 0.08-5.1). There were no differences in outcomes between patients with sustained versus unsustained improvement.Conclusions: UAD improved in half of patients following BMZ. Lack of UAD improvement was associated with shorter latency and earlier gestational age at delivery, but no difference in composite neonatal morbidity. UAD response to BMZ may be useful to further risk stratify FGR pregnancies.

Chronic glucocorticoid exposure potentiates placental chorionic plate artery constriction: implications for aberrant fetoplacental vascular resistance in fetal growth restriction

Fetal growth restriction (FGR) is a serious pregnancy complication, resulting in significant perinatal morbidity and mortality. Increased vascular resistance in the fetoplacental circulation is a hallmark of FGR and is associated with enhanced vasoconstriction of the resistance arteries in the placenta, the chorionic plate arteries (CPAs). Although the cause is unknown, FGR is associated with excess exposure to glucocorticoids (GCs), key mediators of vascular resistance in the systemic circulation. We hypothesized that GCs alter CPA reactivity, thereby contributing to the altered blood flow dynamics seen in FGR. We aimed to examine the acute and chronic effects of GCs on CPA reactivity and the operational mechanisms. Glucocorticoid receptors were highly expressed by CPA. 11β-Hydroxysteroid isoenzyme type 2 was detected within the endothelium, whereas 11β-hydroxysteroid isoenzyme type 1 was absent. Acute GC treatment significantly attenuated U46619-induced constriction. This effect was reversed by cotreatment with mifepristone or an endothelial NOS inhibitor. In contrast, chronic GC treatment potentiated U46619 constriction in a dose-dependent manner, which was partially abolished by mifepristone cotreatment. Similar effects were observed using a novel nonsteroidal glucocorticoid receptor-specific agonist. Chronic treatment with GCs altered the expression of several vasoactive factors, including thromboxane and bradykinin receptors, prokineticin-1, cyclooxygenase-2, and endothelial NOS. In summary, acute and chronic GC treatment exerts contrasting effects on CPA vasoreactivity. These opposing effects are consistent with temporal actions in other vascular beds and reflect activation of distinct nongenomic and genomic pathways. Chronic exposure to elevated GCs may contribute to the raised vascular resistance observed in the fetoplacental circulation in FGR.

Potential risks and benefits of antenatal corticosteroid therapy prior to preterm birth in pregnancies complicated by severe fetal growth restriction

The antepartum administration of fluorinated corticosteroids for fetal maturation represents the most important clinical contribution in the battle against prematurity. This treatment reduces the risk of neonatal death and handicap. It is also known that on corticosteroid exposure, fetuses are subjected to transiently increased physiologic and metabolic demands. Healthy fetuses are able to cope, although emerging evidence suggests this may not be the case with severely growth-restricted fetuses. This review presents evidence of efficacy and safety pertaining to corticosteroid administration in fetal growth restriction–affected pregnancies, offers guidance to clinicians, and points out questions that still need answers.

Cardiovascular responses to maternal betamethasone administration in the intrauterine growth-restricted ovine fetus

OBJECTIVE

The objective was to characterize the effect of glucocorticoid treatment on fetal organ blood flow and regional cerebral blood flow in normally grown fetuses and fetuses with intrauterine fetal growth restriction (IUGR).

STUDY DESIGN

Studies were undertaken in both control and IUGR fetal sheep; growth restriction was induced by ligation of 1 umbilical artery. Fetuses received colored microspheres for organ blood flow calculations before and after 2 maternal betamethasone injections (BM1 and BM2).

RESULTS

Following BM1, cardiac output was significantly decreased in the control fetuses and blood flow to the heart and placenta was unchanged, whereas total cerebral blood flow was significantly decreased (P<.001), consistent with cerebral vasoconstriction. In the fetuses with IUGR, the cardiac output was significantly increased at +33 hours relative to BM1, and blood flow was increased in all organs; notably, there was a 2-fold increase in cerebral blood flow (P=.03).

CONCLUSION

The cardiovascular response of the fetus with IUGR to glucocorticoids is profoundly different from the control fetuses, which may induce both short- and long-term injury.

Antenatal corticosteroids increase fetal, but not postnatal, pulmonary blood flow in sheep

The lungs of very preterm infants have immature airways and gas exchange structures and are usually surfactant deficient. Antenatal corticosteroids are commonly used to enhance fetal lung maturation in preterm infants, but little is known of their effects on pulmonary blood flow (PBF) before and immediately after birth. Our aim was to determine the effects of antenatal betamethasone on PBF before birth and during the postnatal transition in very preterm lambs. Antenatal betamethasone treatment significantly increased mean fetal PBF from 20.2 +/- 5.1 to 84.3 +/- 18.3 mL/min at 30 h after administration; the PBF waveform was also significantly altered. Mean diastolic PBF increased from -38.5 +/- 4.9 pretreatment to -10.2 +/- 11.0 mL/min at approximately 36 h after the initial betamethasone dose (negative values indicate retrograde flow away from the lungs). Within 10 min after delivery, PBF was similar in control and betamethasone-treated lambs. These data demonstrate that antenatal betamethasone significantly increases fetal PBF and alters the PBF waveform but has little effect on postnatal PBF.

Predicting perinatal outcome through changes in umbilical artery Doppler studies after antenatal corticosteroids in the growth-restricted fetus

OBJECTIVE

To investigate whether persistently absent umbilical artery end-diastolic flow in the intrauterine growth-restricted fetus after betamethasone administration is associated with altered perinatal outcomes.

METHODS

This is a retrospective cohort study of 92 pregnancies complicated by intrauterine growth restriction (IUGR) and absent end-diastolic flow in which antenatal betamethasone was given. Predefined maternal outcomes (maternal age, gestational age at diagnosis of absent end-diastolic flow, gestational age at delivery, preexisting medical conditions) and neonatal outcomes (including birth weight; perinatal mortality; duration of neonatal intensive care unit admission; requirement for intubation, assisted ventilation, inotropic support; duration of supplemental oxygen, assisted ventilation; respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage) were analyzed.

RESULTS

Betamethasone administration was associated with a transient return of end-diastolic umbilical artery flow in 58 pregnancies (63%) and persistent absent end-diastolic flow in 34 (37%). Persistent absent end-diastolic flow was seen more frequently in women with prepregnancy medical disorders (59% compared with 24%, P<.001). Neonates from the persistent absent end-diastolic flow subgroup were more likely to require assisted ventilation (93.1% compared with 73.5%, P=.03) and to have longer durations of assisted ventilation (median time 30 days compared with 4 days, P=.03) and supplemental oxygen (median time 45 days compared with 4 days, P=.04).

CONCLUSION

Betamethasone administration is associated with a transient return of end-diastolic flow in two thirds of pregnancies complicated by IUGR and umbilical artery absent end-diastolic flow. Persistent absent end-diastolic flow in the umbilical artery after betamethasone administration may identify a subgroup of fetuses with IUGR at further heightened perinatal risk that, as neonates, are more likely to require assisted ventilation and a longer duration of ventilation and supplemental oxygen.

Umbilical artery tone in maternal obesity

BACKGROUND

The increasing prevalence of obesity constitutes a major health problem in obstetrics with implications for feto-maternal growth and wellbeing. This study investigated and compared the contractile properties of umbilical arteries excised from obese women, with those excised from women with a normal body mass index (BMI).

METHODS

Sections of umbilical artery were obtained from umbilical cord samples immediately after delivery and mounted for isometric recording in organ tissue baths under physiological conditions. Cumulative additions of 5-Hydroxytryptamine (5-HT) and Prostaglandin F-2alpha (PgF2alpha) were added in the concentration range of 1 nmol/L to 10 micromol/L. Control vessels were exposed to Krebs physiological salt solution (PSS) only. The resultant effects of each drug addition were measured using the Powerlab hardware unit.

RESULTS

5-HT exerted a significant effect on human umbilical artery tone at concentrations of 100 nmol/L, 1 micromol/L, and 10 micromol/L in normal (n = 5; P < 0.05) and obese (n = 5; P < 0.05) women. The contractile effect was significantly greater in vessels from obese women {Mean Maximum Tension (MMT) = 4.2532 g} than in those from women of normal BMI (MMT = 2.97 g; P < 0.05). PgF2alpha exerted a significant contractile effect on vessels at 1 micromol/L and 10 micromol/L concentrations when compared with controls (n = 5; P < 0.05). There was a non-significant trend towards an enhanced tone response in vessels from obese women (MMT = 3.02 g; n = 5), in comparison to vessels from women of a normal BMI (MMT = 2.358 g; n = 5; P > 0.05).

CONCLUSION

These findings support the hypothesis that endogenous regulation of umbilical artery tone is altered in association with maternal obesity. This may be linked to the cardiovascular effects of secretory products of adipose tissue, with implications for the feto-maternal circulation.

Maternal asthma and placental morphometry: effects of severity, treatment and fetal sex

Asthma is the most common respiratory disease to complicate pregnancy. Although adverse effects on the fetus have been documented, there is a paucity of information regarding the effects of asthma, and its treatment, on placental morphology. The aim of this study was to test for volumetric differences in placental composition between non-asthmatic pregnancies and those associated with maternal asthma grouped according to asthma severity and glucocorticoid (GC) treatment. Each placenta was weighed and random samples of tissue were fixed in formalin-saline, embedded in wax and analysed by design-based stereology. Volume densities of parenchymal compartments (peripheral villi and maternal intervillous space) and residual non-parenchyma were estimated by test point counting and converted to absolute volumes by taking into account placental size. Relative and absolute lengths of villi and capillaries were also estimated and used to derive secondary quantities related to villous capillarization and maturation. Between-group comparisons were drawn by two-way analysis of variance with group and fetal sex as the principal factors. Compared to non-asthmatic controls, asthmatics had reduced absolute volumes of fetal capillaries which was most marked in those with moderate/severe asthma and those using low and high doses of inhaled GCs. Changes in the total length and mean cross-sectional area of capillaries and peripheral villi were also observed. Lengths were greater in mild asthmatics and lowest in those with high GC usage. Calibre areas were lower in mild asthmatics and villous calibres in the high GC group were greater than those in asthmatics not taking GCs. Those making greatest use of inhaled GCs also had villi which were hypovascularized in terms of capillary:villus length ratios. The findings suggest that the morphometric differences in fetoplacental vascularity are likely to be due to the effects of asthma and use of inhaled GCs rather than the effects of maternal or fetal hypoxic stress.

Endocrine regulation of human fetal growth: the role of the mother, placenta, and fetus

The environment in which the fetus develops is critical for its survival and long-term health. The regulation of normal human fetal growth involves many multidirectional interactions between the mother, placenta, and fetus. The mother supplies nutrients and oxygen to the fetus via the placenta. The fetus influences the provision of maternal nutrients via the placental production of hormones that regulate maternal metabolism. The placenta is the site of exchange between mother and fetus and regulates fetal growth via the production and metabolism of growth-regulating hormones such as IGFs and glucocorticoids. Adequate trophoblast invasion in early pregnancy and increased uteroplacental blood flow ensure sufficient growth of the uterus, placenta, and fetus. The placenta may respond to fetal endocrine signals to increase transport of maternal nutrients by growth of the placenta, by activation of transport systems, and by production of placental hormones to influence maternal physiology and even behavior. There are consequences of poor fetal growth both in the short term and long term, in the form of increased mortality and morbidity. Endocrine regulation of fetal growth involves interactions between the mother, placenta, and fetus, and these effects may program long-term physiology.

Betamethasone effects on ovine uterine and umbilical placental perfusion at the dose used to enhance fetal lung maturation

OBJECTIVE

The purpose of this study was to examine glucocorticoid effects on umbilical placental perfusion.

STUDY DESIGN

Pregnant sheep instrumented with uterine and umbilical ultrasound transit-time flow probes received 2 doses of 12 mg betamethasone (n = 6) or saline (n = 5) intramuscularly 24 hours apart.

RESULTS

Maternal blood pressure and uterine flow did not change during glucocorticoid exposure. Fetal blood pressure increased, and umbilical resistance showed a transient increase after each injection (P < .05), followed by an increase of umbilical flow (P < .05) that was closely correlated to an increase in fetal heart rate (r = 0.85, P < .001), which determines cardiac output of the developing heart. Umbilical waveform indices were decreased over the entire treatment period, indicating a decrease of resistance in the fetoplacental microcirculation (P < .05).

CONCLUSION

Fetoplacental perfusion during glucocorticoid exposure is not limiting for nutrition exchange. Clinical interpretation of Doppler waveform indices needs to be interpreted with caution because they do not reflect dynamics of umbilical placental perfusion.

Corticosteroids, pregnancy, and HELLP syndrome: a review

Corticosteroids are potent antiinflammatory and immunosuppressive drugs, which are used in the treatment of a wide range of medical disorders. During pregnancy, several corticosteroids are administered for maternal as well as fetal reasons. Prednisone and prednisolone show limited transplacental passage and are thus used for treatment of maternal disease. Dexamethasone and betamethasone, drugs that can easily cross the placenta, are more suitable for fetal indications. During the last decade, administration of corticosteroids was introduced in the treatment of hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome), a severe form of preeclampsia unique to human pregnancy. Several randomized, controlled trials as well as other prospective and retrospective studies have been performed to investigate this beneficial effect of corticosteroids on biochemical measures and clinical signs. This review discusses the characteristics of corticosteroids in humans and details the use of corticosteroids during pregnancy. A review of literature on the effect of corticosteroids on HELLP syndrome is given and possible mechanisms of action are discussed.

Effects of thrombin, PAR-1 activating peptide and a PAR-1 antagonist on umbilical artery resistance in vitro

Background

The non-thrombotic effects of thrombin in cardiovascular tissues, as mediated via the protease activated receptors (PARs), and particularly PAR-1, have been the focus of much recent research. The aims of this study were to evaluate the effects of thrombin, a specific PAR-1 activating peptide (PAR1-AP), and a PAR-1 antagonist on human umbilical artery tone in vitro.

Methods

Human umbilical artery samples were obtained from 17 women at term. Arterial rings were suspended under physiologic conditions for isometric recording. The in vitro effects of thrombin (0.5 units/mL to 3 units/mL), PAR1-AP TFLLR-NH2 [10(-9) to 10(-6) M], and PAR-1 antagonist (N-trans cinnamoyl- p-fluoroPhe-p-guanidinoPhe-Leu-Arg-Orn-NH2) [10(-9) M to 10(-5) M] on umbilical artery tone were measured.

Results

Both thrombin and TFLLR-NH2 exerted a potent cumulative vasodilatory effect on human umbilical artery resistance (P < 0.001). The mean net maximal inhibition (MMI) for thrombin was 53.05% (n = 6; SEM = 1.43) at tissue bath concentration of 3 units/mL. The MMI with TFLLR-NH2 was 61.50 % (n = 6; SEM = 1.43) at bath concentration of 10(-6) M. In comparison to vehicle control, the PAR-1 antagonist did not show a significant relaxant or contractile effect (P > 0.05).

Conclusion

These findings highlight a potential role for thrombin and PAR-1 receptors in vascular regulation of feto-placental blood flow in normal pregnancy, and in association with the vascular lesions associated with IUGR and pre-eclampsia.

Effects of thyrotropin-releasing hormone on human myometrium and umbilical vasculature in vitro

OBJECTIVE

The purpose of this study was to investigate the direct effects of thyrotropin-releasing hormone on isolated human myometrium that was obtained during pregnancy and on human umbilical vasculature in vitro.

STUDY DESIGN

Isolated human myometrial strips were dissected from biopsy specimens that were obtained at elective cesarean delivery and suspended for isometric recording under physiologic conditions. The effects of cumulative additions of thyrotropin-releasing hormone (10(-9)-10(-4) mol/L) on oxytocin-induced myometrial contractility were evaluated. The effects of thyrotropin-releasing hormone (10(-9)-10(-4) mol/L) on umbilical vessel (artery and vein) resistance in vitro were investigated with the use of isolated ring preparations.

RESULTS

Thyrotropin-releasing hormone exerted a significant concentration-dependent relaxant effect on pregnant human myometrial tissue, which ranged from 3.54% (10(-9) mol/L, P=.935) to a net cumulative total of 21.06% (10(-4) mol/L, P<.001). Thyrotropin-releasing hormone also exerted a concentration-dependent relaxant effect on human umbilical vasculature that ranged from 12.51% (10(-9) mol/L, P=.994) to a net cumulative total of 23.27%+/-4.87% (SEM, 10(-4) mol/L, P<.01) in umbilical artery. For umbilical vein, the relaxant effect ranged from 1.80% (10(-9) mol/L, P=.998) to a net cumulative total of 14.64% (10(-4) mol/L, P<.009).

CONCLUSION

Thyrotropin-releasing hormone exerts a significant relaxant effect in human myometrium and in human umbilical vasculature and highlights a potential physiologic role for this neuropeptide in these tissues. These findings have clinical implications for the therapeutic use of thyrotropin-releasing hormone antenatally.

Betamethasone associated changes in umbilical artery flow velocity waveforms in multiple pregnancies with umbilical artery absent end diastolic flow

OBJECTIVES

It has been previously shown that glucocorticoids alter umbilical artery flow velocity waveforms in singleton pregnancies complicated by umbilical artery absent end diastolic flow. Whether similar effects are evident in multiple pregnancies where one fetus has umbilical artery absent end diastolic flow is not known.

METHODS

Women with a twin or triplet pregnancy complicated by umbilical artery absent end diastolic flow in one fetus were admitted to hospital for intensive fetal surveillance including daily umbilical artery flow velocity waveform studies, as per hospital protocol. All women received prophylactic betamethasone (11.4 mg x 2, 24 h apart) in anticipation of preterm delivery.

RESULTS

Between October 1996 and February 2002, 24 women with a multiple pregnancy complicated by umbilical artery absent end diastolic flow were cared for. Of these, six had a pregnancy with feto-fetal transfusion and excluded from further analysis. Of the remaining 18 women, eight had monochorionic diamniotic twins, eight had dichorionic twins, and two had trichorionic, triamniotic triplets. The median (range) gestation at diagnosis of umbilical artery absent end diastolic flow was 210.5 days (173-241). In nine (50%) of the 18 pregnancies the administration of betamethasone was associated with return of umbilical artery end diastolic flow for a median of 5 days. There was no association between this effect and chorionicity. The median (range) interval from diagnosis of umbilical artery absent end diastolic flow to delivery was 11 days (1-46).

CONCLUSIONS

As previously reported in singleton pregnancies, the maternal administration of betamethasone in multiple pregnancies with umbilical artery absent end diastolic flow is associated with a transient return of end diastolic flow.