Growth deficient fetuses with absent or reversed umbilical artery end-diastolic flow are metabolically compromised

Placental Stem Villus Arterial Remodeling Associated with Reduced Hydrogen Sulfide Synthesis Contributes to Human Fetal Growth Restriction

Intrauterine fetal growth restriction (IUGR) is often associated with compromised umbilical arterial flow, indicating increased placental vascular resistance. Oxidative stress is causatively implicated. Hydrogen sulfide maintains differentiated smooth muscle in vascular beds, and its synthetic enzyme cystathionine-γ-lyase (CSE) is down-regulated in growth-restricted placentas. We hypothesized that remodeling of resistance arteries in stem villi contributes to IUGR by compromising umbilical blood flow via oxidative stress, reducing hydrogen sulfide signaling. Stem villus arteries in human IUGR placentas displaying absent or reversed end-diastolic flow contained reduced myosin heavy chain, smooth muscle actin, and desmin, and increased markers of dedifferentiation, cellular retinol-binding protein 1, and matrix metalloproteinase 2, compared to term and preterm controls. Wall thickness/lumen ratio was increased, lumen diameter decreased, but wall thickness remained unchanged in IUGR placentas. CSE correlated positively with myosin heavy chain, smooth muscle actin, and desmin. Birth weight correlated positively with CSE, myosin heavy chain, smooth muscle actin, and desmin, and negatively with cellular retinol-binding protein 1 and matrix metalloproteinase 2. These findings could be recapitulated in vitro by subjecting stem villus artery explants to hypoxia-reoxygenation, or inhibiting CSE. Treatment with a hydrogen sulfide donor, diallyl trisulfide, prevented these changes. IUGR is associated with vascular remodeling of the stem villus arteries. Oxidative stress results in reduction of placental CSE activity, decreased hydrogen sulfide production, and smooth muscle cell dedifferentiation in vitro. This vascular remodeling is reversible, and hydrogen sulfide donors are likely to improve pregnancy outcomes.

Reduced cystathionine γ-lyase and increased miR-21 expression are associated with increased vascular resistance in growth-restricted pregnancies: hydrogen sulfide as a placental vasodilator

Increased vascular impedance in the fetoplacental circulation is associated with fetal hypoxia and growth restriction. We sought to investigate the role of hydrogen sulfide (H₂S) in regulating vasomotor tone in the fetoplacental vasculature. H₂S is produced endogenously by catalytic activity of cystathionine β-synthase and cystathionine γ-lyase (CSE). Immunohistochemical analysis localized CSE to smooth muscle cells encircling arteries in stem villi. Immunoreactivity was reduced in placentas from pregnancies with severe early-onset growth-restriction and preeclampsia displaying abnormal umbilical artery Doppler waveforms compared with preeclamptic placentas with normal waveforms and controls. These findings were confirmed at the protein and mRNA levels. MicroRNA-21, which negatively regulates CSE expression, was increased in placentas with abnormal Doppler waveforms. Exposure of villus explants to hypoxia-reoxygenation significantly reduced CSE protein and mRNA and increased microRNA-21 expression. No changes were observed in cystathionine β-synthase expression, immunolocalized principally to the trophoblast, in pathologic placentas or in vitro. Finally, perfusion of normal placentas with an H₂S donor, after preconstriction with a thromboxane mimetic, resulted in dose-dependent vasorelaxation. Glibenclamide and N^G-nitro-l-arginine methyl ester partially blocked the effect, indicating that H₂S acts through ATP-sensitive K⁺ channels and nitric oxide synthesis. These results demonstrate that H₂S is a powerful vasodilator of the placental vasculature and that expression of CSE is reduced in placentas associated with increased vascular resistance.

Global protein synthesis in human trophoblast is resistant to inhibition by hypoxia

Placental growth and function depend on syncytial cell processes which require the continuing synthesis of cellular proteins. The substantial energy demands of protein synthesis are met primarily from oxidative metabolism. Although the responses of individual proteins produced by the syncytiotrophoblast to oxygen deprivation have been investigated previously, there is no information available on global protein synthesis in syncytiotrophoblast under conditions of hypoxia. These studies were designed to test the hypothesis that syncytial protein synthesis is decreased in a dose-dependent manner by hypoxia. Experiments were performed to measure amino acid incorporation into proteins in primary syncytiotrophoblast cells exposed to oxygen concentrations ranging from 0 to 10%. Compared to cells exposed to normoxia (10% O₂), no changes were observed following exposure to 5% or 3% O₂, but after exposure to 1% O₂, protein synthesis after 24 and 48 h decreased by 24% and 23% and with exposure to 0% O₂, by 65% and 50%. As a consequence of these results, we hypothesized that global protein synthesis in conditions of severe hypoxia was being supported by glucose metabolism. Additional experiments were performed therefore to examine the role of glucose in supporting protein synthesis. These demonstrated that at each oxygen concentration there was a significant, decreasing linear trend in protein synthesis as glucose concentration was reduced. Under conditions of near-anoxia and in the absence of glucose, protein synthesis was reduced by >85%. Even under normoxic conditions (defined as 10% O₂) and in the presence of oxidative substrates, reductions in glucose were accompanied by decreases in protein synthesis. These experiments demonstrate that syncytiotrophoblast cells are resistant to reductions in protein synthesis at O₂ concentrations greater than 1%. This could be explained by our finding that a significant fraction of protein synthesis in the syncytiotrophoblast is sustained by glycolytic metabolism. This suggests that with increasing degrees of chronic hypoxia there is a shift from oxidative to glycolytic pathways, allowing a substantial degree of protein synthesis to be maintained.

Outcome of induced deliveries in growth-restricted fetuses: second thoughts about the vaginal option

OBJECTIVE

To assess the outcome of induced deliveries with IUGR.

STUDY DESIGN

We reviewed the computerized files of parturients who underwent inducted labor because of IUGR (<5th percentile). Outcome assessment included mode of delivery, indication for CS, NICU admissions and 5 min Apgar score. We compared these parameters to a control group of women whose deliveries were induced for other indications.

RESULTS

A total of 836 women with IUGR were included. Mean gestational age and birth weight were 38.2 weeks and 2,114 g, respectively. Overall, 43% of women delivered by non-elective C/S. The rate of non-elective CS for other indications was 12.3% (P < 0.0001) for all deliveries and 23.6% (P < 0.001) for induced deliveries. CS was performed due to non-reassuring FHR in 63% of IUGR fetuses, compared with 27% of all induced deliveries. There were 160 women with IUGR who preferred elective CS. Their newborns' NICU admission and 5 min Apgar score <7 rates were lower than those for induced deliveries (NICU 43.1 and 29.4%, P < 0.05, 5 min Apgar <7 5 and 1%, P < 0.05).

CONCLUSION

Growth-restricted neonates born after labor induction had higher rates of low Apgar scores and NICU admissions compared to growth restricted neonates delivered by elective C/S. Inductions of labor for IUGR were associated with higher rates of non-elective C/S due to non-reassuring fetal heart rate compared with inductions performed for other indications.

Disproportionate Intrauterine Growth Intervention Trial At Term: DIGITAT

Background

Around 80% of intrauterine growth restricted (IUGR) infants are born at term. They have an increase in perinatal mortality and morbidity including behavioral problems, minor developmental delay and spastic cerebral palsy. Management is controversial, in particular the decision whether to induce labour or await spontaneous delivery with strict fetal and maternal surveillance. We propose a randomised trial to compare effectiveness, costs and maternal quality of life for induction of labour versus expectant management in women with a suspected IUGR fetus at term.

Methods/design

The proposed trial is a multi-centre randomised study in pregnant women who are suspected on clinical grounds of having an IUGR child at a gestational age between 36+0 and 41+0 weeks. After informed consent women will be randomly allocated to either induction of labour or expectant management with maternal and fetal monitoring. Randomisation will be web-based. The primary outcome measure will be a composite neonatal morbidity and mortality. Secondary outcomes will be severe maternal morbidity, maternal quality of life and costs. Moreover, we aim to assess neurodevelopmental and neurobehavioral outcome at two years as assessed by a postal enquiry (Child Behavioral Check List-CBCL and Ages and Stages Questionnaire-ASQ). Analysis will be by intention to treat. Quality of life analysis and a preference study will also be performed in the same study population. Health technology assessment with an economic analysis is part of this so called Digitat trial (Disproportionate Intrauterine Growth Intervention Trial At Term). The study aims to include 325 patients per arm.

Discussion

This trial will provide evidence for which strategy is superior in terms of neonatal and maternal morbidity and mortality, costs and maternal quality of life aspects. This will be the first randomised trial for IUGR at term.

Trial registration

Dutch Trial Register and ISRCTN-Register: ISRCTN10363217.

Prognostic Value of Umbilical Artery Doppler Studies in Unselected Preterm Deliveries

OBJECTIVE

To evaluate the prognostic value of umbilical artery Doppler studies in premature deliveries.

METHODS

In this cohort study of 582 singleton pregnancies delivered between 24 and 35 weeks of gestation, we evaluated the ratio of peak-systolic to end-diastolic (S/D) blood flow velocities in the umbilical artery of all the patients. The correlations among the results of the Doppler studies, short-term neonatal complications, and the infants' neurodevelopmental outcome at 2 years were studied by univariable and multivariable methods.

RESULTS

The prevalences of either neonatal death or cerebral palsy among the 266 (45.7%) growth restricted fetuses were 3.4% (3/88) in pregnancies with a S/D ratio below the 95th percentile, 4.9% (5/103) in pregnancies with a S/D at or above the 95th percentile, and 17.3% (13/75) in those with absent or reversed end-diastolic blood flow in the umbilical artery (P for trend = .001). The corresponding figures in the 316 pregnancies with adequate fetal growth were 6.4% (15/234) and 4.3% (3/69) among pregnancies with a S/D ratio below and at or above 95th percentile, respectively, whereas no cases of either neonatal death or cerebral palsy were recorded in the 13 pregnancies with adequate fetal growth and absent or reversed end-diastolic blood flow velocity (P for trend = .28; chi(2) for heterogeneity of linear trends compared with growth-restricted infants = 7.02, P = .008). In logistic regression, in pregnancies complicated by fetal growth restriction, absent or reversed end-diastolic blood flow in the umbilical artery was still associated with an increased risk of either neonatal death or cerebral palsy even after adjustment for gestational age and proportion of expected birth weight, (odds ratio 3.2, 95% confidence interval 1.18-8.66, P = .02).

CONCLUSION

Absent or reversed end-diastolic flow in the umbilical artery is an independent predictor of either neonatal death or cerebral palsy in preterm growth-restricted fetuses. In the absence of fetal growth restriction, umbilical artery Doppler study was associated with none of the infant outcome parameters studied.

Animal models of hypoxic-ischemic brain damage in the newborn

Controversy continues over which animal model to use as a reflection of human disease states. With respect to perinatal brain disorders, scientists must contend with a disease in evolution. In that regard, the perinatal brain is at risk during a time of extremely rapid development and maturation, involving processes that are required for normal growth. Interfering with these processes, as part of therapeutic intervention must be efficacious and safe. To date, numerous models have provided tremendous information regarding the pathophysiology of brain damage to term and preterm infants. Our challenges will continue to be in identifying those infants at greatest risk for permanent injury, and adapting therapies that provide more benefit than harm. Using animal models to conduct these studies will bring us closer to that goal.

Prospect for vaginal delivery of growth restricted fetuses with abnormal umbilical artery blood flow

BACKGROUND

The best mode of delivery in cases of intrauterine growth restriction (IUGR) with umbilical artery blood flow changes is not well elucidated.

OBJECTIVE

To evaluate outcome in IUGR with umbilical artery blood flow changes planned for vaginal delivery after a negative oxytocin challenge test (OCT).

METHODS

In 84 term singleton pregnancies with suspected IUGR and no unanimous indication for abdominal delivery, Doppler velocimetry and OCT were performed. Positive OCT cases were delivered by cesarean section, negative OCT cases planned for vaginal delivery.

RESULTS

Umbilical artery Doppler velocimetry was normal in 51 cases (normal group) and abnormal in 33 cases (increased pulsatility index with maintained forward diastolic flow). Gestational age at delivery was shorter (p = 0.008), positive OCT more common (33% vs. 16%; p = 0.06), and vaginal delivery less common (40% vs. 63%; p = 0.04) in the abnormal blood flow group compared with the normal flow group. When in labor, 68% in the abnormal flow group and 76% in the normal flow group delivered vaginally (p = 0.6). One baby had a lethal malformation and another suffered meconium aspiration and pneumothorax, but was discharged home healthy.

CONCLUSIONS

The vaginal delivery rate was significantly lower in the abnormal flow group compared with the normal flow group, but in cases finally destined for a trial of labor the vaginal delivery rates were similar. There was no indication that any fetus was exposed to detrimental hypoxia or distress.

Absent or reversed end-diastolic blood flow in the umbilical artery and abnormal Doppler cerebroplacental ratio--cognitive, neurological and somatic development at 3 to 6 years

The objective of this study was to examine the cognitive, neurological and somatic developments of children who had in utero an absent or reversed end-diastolic blood flow (ARED) in the umbilical artery or an abnormal cerebroplacental ratio (ABF).

METHODS

16 children with ARED blood flow and 15 children with ABF were each matched to children with the same gestational age, appropriate for gestational age, the same sex and born within 4 months. Data were assessed at the age of 3-6 years. Children with asphyxia, neonatal infection, malformation or major surgical interventions in the neonatal period were excluded. Each child underwent a neuropediatrical examination; furthermore, a Kaufman Assessment Battery for Children, a Snijders-Oomen Intelligence Scale for Children and a Man-Drawing Test were used to evaluate cognitive development. The socioeconomic status was also assessed.

RESULTS

Children in the ARED group remained lighter and had a higher frequency of microcephaly. In the Kaufman Assessment Battery for Children and the Snijders-Oomen Intelligence Scale for Young Children, cognitive development was impaired in the ARED and the ABF groups compared to the control group. The ARED and the ABF groups, however, showed no differences. The Man-Drawing Test and the Denver Development Test did not show any differences.

DISCUSSION

ARED blood flow and ABF showed impaired cognitive development. The degree of impairment was the same in the ARED and the ABF groups. Long-term follow-up studies until adulthood are necessary to see if impaired cognitive development remains significant in these groups of patients.

Angiogenesis and placental growth in normal and compromised pregnancies

Research on the subject of pre-eclampsia has revolved around placental growth and angiogenesis, as both are central to the aetiology of the disease. Vascular angiogenic growth factor (VEGF) is elevated in pre-eclampsia and correlates with the severity of disease. Its actions in vitro mimic the actions of plasma from women with pre-eclampsia. This chapter examines the available evidence that implicates VEGF in the maternal systemic effects seen in pre-eclampsia, and discusses how an understanding of this growth factor could lead to diagnostic and therapeutic options. Oxygenation status is the unifying concept that surrounds the discussion of placental growth and angiogenesis. The concept that 'hypoxia' is too simplistic a notion to describe pre-eclampsia is discussed. Maldevelopment of the angiogenic process can be assessed by Doppler ultrasound. The future may see a role for magnetic resonance imaging in the identification of poorly perfused placenta.

Activity and expression of the Na(+)/H(+) exchanger in the microvillous plasma membrane of the syncytiotrophoblast in relation to gestation and small for gestational age birth

The effect of gestational age, low birth weight, and umbilical plasma pH on the activity and expression of the Na(+)/H(+) exchanger in the microvillous plasma membrane (MVM) of the placental syncytiotrophoblast was investigated. MVM were isolated from placentas of fetuses delivered in the first and second trimesters and from appropriately grown for gestational age (AGA) and small for gestational age (SGA) babies born at term. Na(+)/H(+) exchange activity (amiloride-sensitive Na(+) uptake) was higher (p<0.05) in second trimester and term AGA MVM versus first trimester MVM (median [range]: 1.80 [1.01-3.03], 1.72 [1.16-3.15] versus 1.48 [0.92-1.66] nmol/mg protein/30s, respectively, n = 6, 12, and 9). As regards exchanger isoforms, Western blotting showed that NHE1 expression did not change across gestation, but NHE2 and NHE3 expression were lower (p<0.01) in the first and second trimesters than in term AGA MVM. There were no differences in Na(+)/H(+) exchanger activity or in NHE1-3 expression in term AGA MVM versus SGA (n = 11) MVM. There was no correlation between exchanger activity and umbilical artery or vein plasma pH, although with a relatively small number of samples (n = 12 and 15, respectively). We conclude that there is differential regulation of the activity and expression of Na(+)/H(+) exchanger isoforms in the MVM over the course of gestation in normal pregnancy; this is not affected in pregnancies resulting in SGA babies at term.

Outcome of 88 pregnancies with absent or reversed end-diastolic blood flow (ARED flow) in the umbilical arteries

OBJECTIVES

To investigate both perinatal and postneonatal morbidity and mortality in fetuses with absent or reversed end-diastolic flow (ARED flow) in the umbilical artery.

STUDY DESIGN

A 5 year prospective follow-up of 88 fetuses with ARED flow.

RESULTS

Sixteen stillbirths, 16 neonatal deaths, six postneonatal deaths and one death at 2 years of age were noted. Out of the 42 fetuses born alive, 36 showed a normal neurological development whereas six were mentally handicapped. Adverse prognosis was more frequently found in the group with absent end-diastolic flow at first examination and then reversed flow until delivery, compared to the groups of always absent or always reversed end-diastolic flows.

CONCLUSIONS

Prompt delivery is recommended in these high-risk pregnancies in order to prevent long-term sequelae, obviously depending on the local limits of viability. Further studies appropriately designed for assessing long-term neurodevelopment of fetuses with ARED flow, although demanding, are mandatory.

Oxygen and placental villous development: origins of fetal hypoxia

The increasing practice of preterm delivery in the fetal interest for conditions such as pre-eclampsia or intrauterine growth restriction (IUGR) has provided an opportunity to study placental structure in pregnancies with prenatal evidence of fetal compromise. These data suggest that the origin of fetal hypoxia in IUGR with absent end-diastolic flow in the umbilical arteries is due to a failure of oxygen transport from intervillous space to umbilical vein. Failure of the fetoplacental circulation to extract oxygen from the intervillous space under such circumstances means intervillous PO2 is closer to maternal arterial values than under physiological conditions. Correspondingly the placental villi are chronically exposed to a higher oxygen tension than under normal circumstances--the term ¿hyperoxia', relative to normal intraplacental oxygenation, is proposed to describe this situation. Both the trophoblast and villous core react to increased oxygen despite fetal hypoxia. These results challenge the generally accepted concept of ¿placental hypoxia' in all circumstances where fetal hypoxia might arise. Therefore three categories are proposed for the origins of fetal hypoxia: (1) preplacental hypoxia; (2) uteroplacental hypoxia; and (3) postplacental hypoxia. Examples for these three disease states are listed in this review and the structural reaction patterns of placental villi to these differences in oxygenation are discussed.

Intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery is associated with maldevelopment of the placental terminal villous tree

OBJECTIVE

Our purpose was to evaluate the structure of placental terminal villi and their capillaries in pregnancies complicated by intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery.

STUDY DESIGN

Glutaraldehyde-perfusion-fixed villous tissue and a plastic cast of the vessels in at least two cotyledons were prepared from 10 cases with intrauterine growth restriction and 9 gestational age-matched control placentas. The structure and dimensions of 20 terminal capillary loops per cast were determined by scanning electron microscopic examination, and their appearances were correlated with the peripheral villi of the perfusion-fixed villous tissue.

RESULTS

Capillary loops in the growth-restricted cases were sparse in number and significantly longer than in the control cases (218 microns [72] vs 137 microns [30], mean and SD, p < 0.05). They exhibited fewer branches (4.0 [1.9] per loop vs 6.1 [2.2], p < 0.05) and a majority of loops were uncoiled (79% vs 18%, p < 0.05). The villous tissues from the growth-restricted cases demonstrated elongated villi, consistent with the cast findings. The trophoblast surface was wrinkled and in some areas covered by fibrin plaques.

CONCLUSIONS

The terminal villous compartment of the placenta appears to be maldeveloped in preterm intrauterine growth restriction pregnancies where absent end-diastolic flow velocity is demonstrated in the umbilical artery before delivery. These findings are consistent with an increase in fetoplacental vascular impedance at the capillary level and may account for the impaired gas and nutrient transfer in this disorder.