Sildenafil During Pregnancy

Phosphodiesterase Inhibitors in Fetal Growth Restriction: Do Not Forget to Consider Fetal Sex and Subcellular Compartmentation

Fetal growth restriction (FGR) is a common complication of pregnancy, associated with major perinatal mortality and morbidity, and with an increased risk to develop cardiometabolic diseases later in life. There is currently no effective approach to prevent or treat FGR, despite numerous animal and human studies assessing substances likely to improve fetal growth. Phosphodiesterase (PDE) inhibitors appeared as promising drugs to improve FGR management. However, to date, studies have led to somewhat disappointing or controversial results. In this Opinion article, we would like to draw attention to the need to consider the biological sex and the relative reactivity of human umbilical vein and arteries when developing therapeutic interventions to improve human umbilical circulation using PDE inhibitors. Indeed, we suspect that fetal sex, vessel type and the presence of FGR may influence subcellular compartmentation, which could jeopardize beneficial effects of PDE inhibitors.

The iSEARCH randomised controlled trial protocol: a pragmatic Australian phase III clinical trial of intrapartum sildenafil citrate to improve outcomes potentially related to intrapartum hypoxia

INTRODUCTION

We showed in a phase II randomised controlled trial (RCT) that oral sildenafil citrate in term labour halved operative birth for fetal distress. We outline the protocol for a phase III RCT (can intrapartum SildEnafil safely Avert the Risks of Contraction-induced Hypoxia? (iSEARCH)) of 3200 women in Australia to assess if sildenafil citrate reduces adverse perinatal outcomes related to intrapartum hypoxia.

METHODS AND ANALYSIS

iSEARCH will enrol 3200 Australian women in term labour to determine whether up to three 50 mg oral doses of sildenafil citrate versus placebo reduce the relative risk of a primary composite end point of 10 perinatal outcomes potentially related to intrapartum hypoxia by 35% (from 7% to 4.55%). Secondary aims are to evaluate reductions in the relative risk of emergency caesarean section or instrumental vaginal birth for fetal distress by 25% (from 20% to 15%) and in healthcare costs. To detect a 35% reduction in the primary outcome for an alpha of 0.05 and power of 80% with 10% dropout in each arm requires 3200 women (1600 in each arm). This sample size will also yield >90% power to detect a 25% reduction for the secondary outcome of any operative birth (caesarean section or instrumental vaginal birth) for fetal distress.

ETHICS AND DISSEMINATION

Ethical approval for the iSEARCH RCT was granted by the Hunter New England Human Research Ethics Committee (ref no: 2020/ETH02791). Results will be disseminated through websites, peer-reviewed publications, scientific meetings and social media, news outlets, television and radio.

TRIAL REGISTRATION NUMBER

ACTRN12621000231842.

Safety and efficacy of phosphodiesterase-5 (PDE-5) inhibitors in fetal growth restriction: a systematic literature review and meta-analysis

Introduction: Fetal growth restriction (FGR) is associated with a higher risk of perinatal morbidity and mortality, as well as long-term health issues in newborns. Currently, there is no effective medicine for FGR. Phosphodiesterase-5 (PDE-5) inhibitors have been shown in pre-clinical studies to improve FGR. This study aimed to evaluate the latest evidence about the clinical outcomes and safety of PDE-5 inhibitors for the management of FGR. Methods: Eight databases (PubMed, Embase, Medline, Web of Science, Cochrane Library, Chinese National Knowledge Infrastructure, Chinese Biomedical Database and WangFang Database) were searched for English and Chinese articles published from the database inception to December 2023. Randomized controlled trials (RCTs) reporting the use of PDE-5 inhibitors in FGR were included. The quality of the RCTs was assessed using the Cochrane Risk of Bias Tool. Odds ratio and mean difference (MD) (95% confidence intervals) were pooled for meta-analysis. Results: From 253 retrieved publications, 16 studies involving 1,492 pregnant women met the inclusion criteria. Only sildenafil (15 RCTs) and tadalafil (1 RCT) were studied for FGR. Compared with the control group (placebo, no treatment, or other medication therapies), sildenafil increased birth weight, pregnancy prolongation and umbilical artery pulsatility indices. However, it also increased the risk of pulmonary hypertension in newborns, as well as headache and flushing/rash in mothers. There were no significant differences in gestation age, perinatal mortality or major neonatal morbidity, stillbirth, neonate death, infants admitted to neonatal intensive care unit, intraventricular hemorrhage and necrotizing enterocolitis in infants, as well as pregnancy hypertension and gastrointestinal side effects in mothers between the treatment and the control groups. Discussion: Sildenafil was the most investigated PDE-5 inhibitors for FGR. Current evidence suggests that sildenafil can improve birth weight and duration of pregnancy but at the same time increase the risk of neonatal pulmonary hypertension. It remains uncertain whether the benefits of sildenafil in FGR outweigh the risks and further high-quality RCTs are warranted. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=325909.

Maternal tadalafil treatment does not increase uterine artery blood flow or oxygen delivery in the pregnant ewe

Increasing placental perfusion (PP) could improve outcomes of growth-restricted fetuses. One way of increasing PP may be by using phosphodiesterase (PDE)-5 inhibitors, which induce vasodilatation of vascular beds. We used a combination of clinically relevant magnetic resonance imaging (MRI) techniques to characterize the impact that tadalafil infusion has on maternal, placental and fetal circulations. At 116-117 days' gestational age (dGA; term, 150 days), pregnant ewes (n = 6) underwent fetal catheterization surgery. At 120-123 dGA ewes were anaesthetized and MRI scans were performed during three acquisition windows: a basal state and then ∼15-75 min (TAD 1) and ∼75-135 min (TAD 2) post maternal administration (24 mg; intravenous bolus) of tadalafil. Phase contrast MRI and T2 oximetry were used to measure blood flow and oxygen delivery. Placental diffusion and PP were assessed using the Diffusion-Relaxation Combined Imaging for Detailed Placental Evaluation-'DECIDE' technique. Uterine artery (UtA) blood flow when normalized to maternal left ventricular cardiac output (LVCO) was reduced in both TAD periods. DECIDE imaging found no impact of tadalafil on placental diffusivity or fetoplacental blood volume fraction. Maternal-placental blood volume fraction was increased in the TAD 2 period. FetalD O 2 ${D_{{{\mathrm{O}}_2}}}$ andV ̇ O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ were not affected by maternal tadalafil administration. Maternal tadalafil administration did not increase UtA blood flow and thus may not be an effective vasodilator at the level of the UtAs. The increased maternal-placental blood volume fraction may indicate local vasodilatation of the maternal intervillous space, which may have compensated for the reduced proportion of UtAD O 2 ${D_{{{\mathrm{O}}_2}}}$ .

Effects of sildenafil on Doppler parameters, maternal and neonatal outcomes in the active labor phase of low-risk pregnancies: a randomized clinical trial

OBJECTIVES

The benefits of sildenafil by increasing blood flow in the improvement of Doppler parameters of umbilical (UA), uterine (UtA), and fetal middle cerebral arteries (MCA) remain uncertain. On the other hand, insufficient blood flow during uterine contractions in labor can lead to decrease blood supply and fetal distress. Therefore, we aimed to assess the changes in fetal Doppler indices and maternal and neonatal outcomes following the use of sildenafil in the active phase of labor in low-risk pregnancies with healthy fetuses.

METHODS

This randomized double-blinded controlled trial was conducted on 70 pregnant single low-risk, pregnant women. The patients were randomly assigned into two groups receiving sildenafil (n=35) or placebo (n=35) when the active phase of labor was initiated. Doppler parameters were assessed at baseline as well as 3 h after that. Indeed, the maternal and neonatal outcomes were compared between groups.

RESULTS

The Doppler parameters including the pulsatility index of MCA, UA, and left and right UtA remained unchanged after the administration of sildenafil. Neonatal outcomes including birth weight, PH of the umbilical artery, Apgar score, respiratory distress syndrome, and neonatal intensive care unit admission as well as maternal outcomes such as cesarean section rate and the occurrence of intrapartum/postpartum hemorrhage had no difference between groups.

CONCLUSIONS

The use of sildenafil in the active phase of labor in low-risk pregnancies may not be beneficial in improving Doppler parameters in MCA, umbilical, and uterine arteries and thus may not improve pregnancy outcomes.

Interventions affecting the nitric oxide pathway versus placebo or no therapy for fetal growth restriction in pregnancy

BACKGROUND

Fetal growth restriction (FGR) is a condition of poor growth of the fetus in utero. One of the causes of FGR is placental insufficiency. Severe early-onset FGR at < 32 weeks of gestation occurs in an estimated 0.4% of pregnancies. This extreme phenotype is associated with a high risk of fetal death, neonatal mortality, and neonatal morbidity. Currently, there is no causal treatment, and management is focused on indicated preterm birth to prevent fetal death. Interest has risen in interventions that aim to improve placental function by administration of pharmacological agents affecting the nitric oxide pathway causing vasodilatation.

OBJECTIVES

The objective of this systematic review and aggregate data meta-analysis is to assess the beneficial and harmful effects of interventions affecting the nitric oxide pathway compared with placebo, no therapy, or different drugs affecting this pathway against each other, in pregnant women with severe early-onset FGR.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (16 July 2022), and reference lists of retrieved studies.

SELECTION CRITERIA

We considered all randomised controlled comparisons of interventions affecting the nitric oxide pathway compared with placebo, no therapy, or another drug affecting this pathway in pregnant women with severe early-onset FGR of placental origin, for inclusion in this review.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane Pregnancy and Childbirth methods for data collection and analysis.

MAIN RESULTS

We included a total of eight studies (679 women) in this review, all of which contributed to the data and analysis. The identified studies report on five different comparisons: sildenafil compared with placebo or no therapy, tadalafil compared with placebo or no therapy, L-arginine compared with placebo or no therapy, nitroglycerin compared with placebo or no therapy and sildenafil compared with nitroglycerin. The risk of bias of included studies was judged as low or unclear. In two studies the intervention was not blinded. The certainty of evidence for our primary outcomes was judged as moderate for the intervention sildenafil and low for tadalafil and nitroglycerine (due to low number of participants and low number of events). For the intervention L-arginine, our primary outcomes were not reported. Sildenafil citrate compared to placebo or no therapy (5 studies, 516 women) Five studies (Canada, Australia and New Zealand, the Netherlands, the UK and Brazil) involving 516 pregnant women with FGR were included. We assessed the certainty of the evidence as moderate. Compared with placebo or no therapy, sildenafil probably has little or no effect on all-cause mortality (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.80 to 1.27, 5 studies, 516 women); may reduce fetal mortality (RR 0.82, 95% CI 0.60 to 1.12, 5 studies, 516 women), and increase neonatal mortality (RR 1.45, 95% CI 0.90 to 2.33, 5 studies, 397 women), although the results are uncertain for fetal and neonatal mortality as 95% confidence intervals are wide crossing the line of no effect. Tadalafil compared with placebo or no therapy (1 study, 87 women) One study (Japan) involving 87 pregnant women with FGR was included. We assessed the certainty of the evidence as low. Compared with placebo or no therapy, tadalafil may have little or no effect on all-cause mortality (risk ratio 0.20, 95% CI 0.02 to 1.60, one study, 87 women); fetal mortality (RR 0.11, 95% CI 0.01 to 1.96, one study, 87 women); and neonatal mortality (RR 0.89, 95% CI 0.06 to 13.70, one study, 83 women). L-Arginine compared with placebo or no therapy (1 study, 43 women) One study (France) involving 43 pregnant women with FGR was included. This study did not assess our primary outcomes. Nitroglycerin compared to placebo or no therapy (1 studies, 23 women) One study (Brazil) involving 23 pregnant women with FGR was included. We assessed the certainty of the evidence as low. The effect on the primary outcomes is not estimable due to no events in women participating in both groups. Sildenafil citrate compared to nitroglycerin (1 study, 23 women) One study (Brazil) involving 23 pregnant women with FGR was included. We assessed the certainty of the evidence as low. The effect on the primary outcomes is not estimable due to no events in women participating in both groups.

AUTHORS' CONCLUSIONS

Interventions affecting the nitric oxide pathway probably do not seem to influence all-cause (fetal and neonatal) mortality in pregnant women carrying a baby with FGR, although more evidence is needed. The certainty of this evidence is moderate for sildenafil and low for tadalafil and nitroglycerin. For sildenafil a fair amount of data are available from randomised clinical trials, but with low numbers of participants. Therefore, the certainty of evidence is moderate. For the other interventions investigated in this review there are insufficient data, meaning we do not know whether these interventions improve perinatal and maternal outcomes in pregnant women with FGR.

The effects of sildenafil citrate on intrauterine growth restriction: a systematic review and meta-analysis

BACKGROUND

An increase in vascular resistance of uterine vessels is associated with intrauterine growth restriction (IUGR). Sildenafil citrate, a phosphodiesterase-5 inhibitor that stabilizes cyclic guanosine monophosphate (cGMP) and increases nitric oxide levels, improves placental perfusion by dilation of spiral arteries and is beneficial in managing IUGR. This study aims to determine the effectiveness of sildenafil citrate in improving perinatal outcomes in IUGR pregnancies.

METHODS

Meta-analysis was performed on data extracted from all studies specific to sildenafil citrate in IUGR management, searching relevant articles on PubMed, Medline, Google Scholar, Embase, and Cochrane databases. Publications identified by the manual search, based on references in reviews, were also included. Dichotomous results were presented as risk ratio (95% confidence interval), while continuous results were expressed as mean difference (MD); samples represented by the random effects model.

RESULTS

Nine trials were included where the sildenafil citrate effect was compared with a placebo or no intervention. A significant increase in birth weight [SMD (95% CI), 0.69 (0.31, 1.07)] was seen in IUGR pregnancies managed with sildenafil. However, gestational age (SMD (95% CI), 0.44 (-0.05, 0.94], fetal death rate [RR (95% CI), 0.56 (0.17, 1.79)] in IUGR pregnancies was not changed by sildenafil. Neonatal death [RR (95% CI), 0.93 (0.47, 1.86)] and neonatal intensive care unit (NICU) admissions [RR (95% CI), 0.76 (0.50, 1.17)] were not significantly different between sildenafil and control groups.

CONCLUSION

Sildenafil citrate increases birth weight and prolonged pregnancies but did not affect stillbirth rate, neonatal death, and NICU admission.

TRIAL REGISTRATION

The study was registered in PROSPERO on September 18, 2021 (CRD42021271992).

Novel therapeutic and diagnostic approaches for preeclampsia

PURPOSE OF REVIEW

This review will summarize recent findings relating to the diagnostic approach to preeclampsia and current avenues of research aimed at modifying the underlying disease process.

RECENT FINDINGS

Growing international consensus supports a broad preeclampsia definition that incorporates maternal end-organ and uteroplacental dysfunction. Recent evidence demonstrates that this definition better identifies women and babies at risk of adverse outcomes compared to the traditional definition of hypertension and proteinuria. Multiple studies have demonstrated the usefulness and cost-effectiveness of angiogenic biomarkers such as soluble fms-like tyrosine kinase-1 and placental growth factor as a clinical adjunct to diagnose and predict severity of preeclampsia associated outcomes. Current novel therapeutic approaches to preeclampsia target pathogenic pathways (e.g. antiangiogenesis) or downstream effects such as oxidative stress and nitric oxide. Recent findings relating to these promising candidates are discussed. Multicenter clinical trials are needed to evaluate their effectiveness and ability to improve fetal and maternal outcomes.

SUMMARY

We provide an updated framework of the current approaches to define and diagnose preeclampsia. Disease modifying therapies (in particular, targeting the angiogenic pathway) are being developed for the first time and promise to revolutionize the way we manage preeclampsia.

Statins in pre-eclampsia or fetal growth restriction: A systematic review and meta-analysis on maternal blood pressure and fetal growth across species

BACKGROUND

Several human randomised controlled trials (RCTs) are investigating the effects of statins on pre-eclampsia (PE) and fetal growth restriction (FGR). This cross-species meta-analysis summarises the preclinical evidence of statin use for PE and FGR.

OBJECTIVES

Evaluate the effects of statins on maternal blood pressure (MBP) and birthweight (BW) in pregnancies complicated by PE or FGR.

SEARCH STRATEGY

PubMed and Embase.com were searched on 10 May 2022 using 'statins' and 'pregnancy'.

SELECTION CRITERIA

We included RCTs and cohorts with matched control groups as well as animal studies.

DATA COLLECTION AND ANALYSIS

The main outcomes were MBP in mmHg and BW in grams. The standardised mean difference (SMD) with a 95% confidence interval (CI) was calculated. Subgroup analyses on species, statin, dose, timing and route of administration were performed if subgroups included at least three studies.

MAIN RESULTS

Our data included one human and 12 animal studies. Prenatal administration of statins significantly reduced MBP during pregnancy (SMD  -2.49 mmHg [95% CI -4.26 to -0.71], p = 0.01). There was no significant effect of statins on BW (SMD 0.69 [95% CI -0.65 to 2.03], p = 0.28). Our subgroup analyses showed no effect on MBP of different doses, species or route of administration.

CONCLUSIONS

Our cross-species meta-analyses demonstrate that statins only reduce maternal blood pressure in rodent pregnancies complicated by pre-eclampsia or fetal growth restriction and have no effect on birthweight across species. The broad confidence intervals, inconsistent direction of the observed effects across the studies and large risk of bias lead us to conclude that a solid base for further human RCTs is lacking.

Effect of pentaerythritol tetranitrate (PETN) on the development of fetal growth restriction in pregnancies with impaired uteroplacental perfusion at midgestation-a randomized trial

BACKGROUND

Fetal growth restriction is strongly associated with impaired placentation and abnormal uteroplacental blood flow. Nitric oxide donors such as pentaerythritol tetranitrate are strong vasodilators and protect the endothelium. Recently, we demonstrated in a randomized controlled pilot study a 38% relative risk reduction for the development of fetal growth restriction or perinatal death following administration of pentaerythritol tetranitrate to pregnant women at risk, identified by impaired uterine perfusion at midgestation. Results of this monocenter study prompted the hypothesis that pentaerythritol tetranitrate might have an effect in pregnancies with compromised placental function as a secondary prophylaxis.

OBJECTIVE

This study aimed to test the hypothesis that the nitric oxide donor pentaerythritol tetranitrate reduces fetal growth restriction and perinatal death in pregnant women with impaired placental perfusion at midgestation in a multicenter trial.

STUDY DESIGN

In this multicenter, randomized, double-blind, placebo-controlled trial, 2 parallel groups of pregnant women presenting with a mean uterine artery pulsatility index >95th percentile at 19+0 to 22+6 weeks of gestation were randomized to 50-mg Pentalong or placebo twice daily. Participants were assigned to high- or low-risk groups according to their medical history before randomization was performed block-wise with a fixed block length stratified by center and risk group. The primary efficacy endpoint was the composite outcome of perinatal death or development of fetal growth restriction. Secondary endpoints were neonatal and maternal outcome parameters.

RESULTS

Between August 2017 and March 2020, 317 participants were included in the study and 307 were analyzed. The cumulative incidence of the primary outcome was 41.1% in the pentaerythritol tetranitrate group and 45.5% in the placebo group (unadjusted relative risk, 0.90; 95% confidence interval, 0.69-1.17; adjusted relative risk, 0.90; 95% confidence interval, 0.69-1.17; P=.43). Secondary outcomes such as preterm birth (unadjusted relative risk, 0.73; 95% confidence interval, 0.56-0.94; adjusted relative risk, 0.73; 95% confidence interval, 0.56-0.94; P=.01) and pregnancy-induced hypertension (unadjusted relative risk, 0.65; 95% confidence interval, 0.46-0.93; adjusted relative risk, 0.65; 95% confidence interval, 0.46-0.92; P=0.01) were reduced.

CONCLUSION

Our study failed to show an impact of pentaerythritol tetranitrate on the development of fetal growth restriction and perinatal death in pregnant women with impaired uterine perfusion at midgestation. Pentaerythritol tetranitrate significantly reduced secondary outcome parameters such as the incidence of preterm birth and pregnancy-induced hypertension in these pregnancies.

Emerging pharmacologic interventions for pre-eclampsia treatment

INTRODUCTION

Pre-eclampsia is a serious pregnancy complication and a major global concern for the mortality of both mother and fetus. Existing symptomatic treatments do not delay disease progression; thus, timely delivery of the baby is the most effective measure. However, the risk of various maternal and fetal injuries remains.

AREAS COVERED

In this review, we summarize the potential strategies for pharmacologic interventions in pre-eclamptic therapy. Specifically, we discuss the pathophysiological process of various effective candidate therapeutics that act on potential pathways and molecular targets to inhibit key stages of the disease. We refer to this pathogenesis-focused drug discovery model as a pathogenesis-target-drug (P-T-D) strategy. Finally, we discuss the introduction of nanotechnologies to improve the safety and efficacy of therapeutics via their specific placental targeting ability and placental retention effects.

EXPERT OPINION

Despite the active development of novel pharmacological treatments based on our current knowledge of pre-eclamptic pathogenesis, investigations are still in the early phase. Thus, further exploration of the pathological mechanisms, integrated with the P-T-D strategy and novel nanosystems, could encourage the development of more effective and safer strategies. Such advances could lead to a shift from expectant management to mechanistic-based therapy for pre-eclampsia.

Sildenafil during the 2nd and 3rd Trimester of Pregnancy: Trials and Tribulations

Sildenafil, a phosphodiesterase 5 inhibitor with a vasodilatory and anti-remodeling effect, has been investigated concerning various conditions during pregnancy. Per indication, we herein review the rationale and the most relevant experimental and clinical studies, including systematic reviews and meta-analyses, when available. Indications for using sildenafil during the second and third trimester of pregnancy include maternal pulmonary hypertension, preeclampsia, preterm labor, fetal growth restriction, oligohydramnios, fetal distress, and congenital diaphragmatic hernia. For most indications, the rationale for administering prenatal sildenafil is based on limited, equivocal data from in vitro studies and rodent disease models. Clinical studies report mild maternal side effects and suggest good fetal tolerance and safety depending on the underlying pathology.

Effectiveness of pentoxifylline in severe early-onset fetal growth restriction: A randomized double-blinded clinical trial

OBJECTIVE

Management of pregnancy complicated by severe early-onset fetal growth restriction (FGR) is one of the most challenging obstetrical issues. So far, there has not been a proven option for the treatment or improvement of this condition. Improper immune response during placentation leads to inadequate trophoblast invasion and impaired utero-placental perfusion. Pentoxifylline improves the endothelial function and induces vasodilation by reducing the inflammatory-mediated cytokines. We have evaluated the effect of Pentoxifylline on fetal-placental perfusion, neonatal outcome, and the level of oxidative stress markers before and after the intervention in the setting of severe early-onset FGR.

MATERIALS AND METHODS

This study is a pilot randomized clinical trial on 40 pregnant women who had developed early-onset growth restricted fetus. Pentoxifylline and placebo were given with a dose of 400 mg per os two times daily until delivery. Serial ultrasound examination regarding fetal weight, amniotic fluid and also utero-placenta-fetal Doppler's were done. For the assessment of serum Antioxidant level, blood sampling was done once at the beginning of the study and again, at least, three weeks after the investigation. After delivery, umbilical-cord blood gas analysis, APGAR score at 1 and 5 min, NICU admission, and neonatal death were recorded and compared between the two groups.

RESULTS

Utero-placenta-fetal Doppler's in the Pentoxifylline group did not significantly change compared to the control group. Fetal weight gain was significantly higher in the Pentoxifylline group before (996.33 ± 317.41) and after (1616.89 ± 527.90) treatment (P = 0.002). Total serum antioxidant capacity significantly increased in the Pentoxifylline group (p < 0.036). Average 5 min Apgar score was significantly higher (P < 0.036) and the percentage of babies admitted to NICU was significantly lower (P < 0.030) in the treated group.

CONCLUSION

Using Pentoxifylline in pregnancy affected by FGR might show promising effects. In this study, Pentoxifylline improved the neonatal outcome, increased fetal weight gain, and reduced neonatal mortality by decreasing the level of oxidative stress markers and cutting down the inflammatory cascade.

Evaluation of bone marrow-derived cell-based therapies in the hindlimb ischaemia model: a protocol for a systematic review and meta-analysis

Objective

Bone marrow(BM)-derived cell-based therapies for critical limb ischamia showed less clinical benefit than expected. While this might be due to patient-specific factors, it remains possible that important details were lost in the bench-to-clinic translation. The hindlimb ischaemia model is the golden standard to evaluate cell-based therapies aimed at promoting neovascularisation. To inform future trial design and identify potential knowledge gaps, we propose a systematic review and meta-analysis of preclinical evidence to assess the efficacy of BM-derived cell administration in restoring relative perfusion in the hind limb model and identify determinants of therapeutic efficacy.

Search strategy

PubMed and EMBASE were searched for prospective studies in which the hindlimb ischaemia model was used to assess BM-derived therapies.

Screening and annotation

Studies with an outcome measure related to relative perfusion of the hindlimb will be included. Study characteristics which include model-related factors as well as details on BM therapy will be extracted.

Data management and reporting

For the primary analysis, a random effects model will be constructed using the mean difference calculated from the maximum relative perfusion for each study arm in each study. A separate model will be constructed using the relative perfusion at the latest time point in each study. We will also assess the risk of bias using the SYRCLE tool for internal validity. Subgroup analysis will be performed on animal characteristics, administration route, dose and cell characteristics such as the cell donor.

PROSPERO registration number

This protocol has been registered at PROSPERO (CRD2021226592).

Progress in preeclampsia: the contribution of animal models

Recent advances have been made in understanding the nature of placental dysfunction causing preeclampsia, and other hypertensive disorders of pregnancy. The contribution of animal studies in the understanding of the effects of inadequate placentation on blood pressure and other target organs will be explored in this review. This will include technical aspects of animal studies in pregnancy, as well as the translation of data regarding newly discovered pathological pathways, in particular the angiogenic pathway, into targets in clinical practice.

Short-term outcomes of phosphodiesterase type 5 inhibitors for fetal growth restriction: a study protocol for a systematic review with individual participant data meta-analysis, aggregate meta-analysis, and trial sequential analysis

BACKGROUND

Early onset fetal growth restriction secondary to placental insufficiency can lead to severe maternal and neonatal morbidity and mortality. Pre-clinical studies and a few small randomised clinical trials have suggested that phosphodiesterase type 5 (PDE-5) inhibitors may have protective effects against placental insufficiency in this context; however, robust evidence is lacking. The STRIDER Consortium conducted four randomised trials to investigate the use of a PDE-5 inhibitor, sildenafil, for the treatment of early onset fetal growth restriction. We present a protocol for the pre-planned systematic review with individual participant data meta-analysis, aggregate meta-analysis, and trial sequential analysis of these and other eligible trials. The main objective of this study will be to evaluate the effects of PDE-5 inhibitors on neonatal morbidity compared with placebo or no intervention among pregnancies with fetal growth restriction.

METHODS

We will search the following electronic databases with no language or date restrictions: OVID MEDLINE, OVID EMBASE, the Cochrane Controlled Register of Trials (CENTRAL), and the clinical trial registers Clinicaltrials.gov and World Health Organisation International Clinical Trials Registry Platform (ICTRP). We will identify randomised trials of PDE-5 inhibitors in singleton pregnancies with growth restriction. Two reviewers will independently screen all citations, full-text articles, and abstract data. Our primary outcome will be infant survival without evidence of serious adverse neonatal outcome. Secondary outcomes will include gestational age at birth and birth weight z-scores. We will assess bias using the Cochrane Risk of Bias 2 tool. We will conduct aggregate meta-analysis using fixed and random effects models, Trial Sequential Analysis, and individual participant data meta-analysis using one- and two-stage approaches. The certainty of evidence will be assessed with GRADE.

DISCUSSION

This pre-defined protocol will minimise bias during analysis and interpretation of results, toward the goal of providing robust evidence regarding the use of PDE-5 inhibitors for the treatment of early onset fetal growth restriction.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (CRD42017069688).

The effect of phosphodiesterase-5 inhibitors on uteroplacental and fetal cerebral perfusion in pregnancies with fetal growth restriction: A systematic review and meta-analysis

OBJECTIVES

To evaluate the effect of phosphodiesterase-5 (PDE-5) inhibitors on uteroplacental and fetal cerebral perfusion in pregnancies complicated with fetal growth restriction (FGR).

MATERIAL AND METHODS

Relevant databases were searched from inception up to June 2021. The random-effects model was used to pool the weighted mean differences (WMDs) and the corresponding 95% confidence intervals (CIs). The primary outcomes were the effect of PDE-5 inhibitors on uterine (UtA-PI), umbilical (UA-PI) and middle cerebral artery (MCA-PI) pulsatility indices. Subgroup analyses were also performed based on the type of PDE-5 inhibitor medication, the dosage of medication, duration of treatment, sample size and onset of FGR.

RESULTS

Seven clinical trials were eligible, 6 trials using sildenafil, and one using tadalafil. The random-effects models indicated PDE-5 inhibitors significantly decrease UtA-PI (WMD = -0.28, 95% CI = -0.46,-0.11) and UA-PI (WMD = -0.07, 95% CI = -0.13, -0.01); however it failed to show a significant effect on MCA-PI (WMD = 0.24, 95% CI = -0.63, 1.11). Subgroup analyses showed similar significant effects of sildenafil on UtA-PI and UA-PI; however, no significant effect was observed after treatment with tadalafil.

CONCLUSION

PDE-5 inhibitors administration, especially sildenafil, may improve uteroplacental, but not fetal cerebral blood perfusion in pregnancies complicated by FGR.

Sildenafil Citrate Downregulates PDE5A mRNA Expression in Women with Recurrent Pregnancy Loss without Altering Angiogenic Factors-A Preliminary Study

In our previous study, we showed that sildenafil citrate (SC), a selective PDE5A blocker, modulated NK cell activity in patients with recurrent pregnancy loss, which correlated with positive pregnancy outcomes. It was found that NK cells had a pivotal role in decidualization, angiogenesis, spiral artery remodeling, and the regulation of trophoblast invasion. Thus, in the current study, we determined the effects of SC on angiogenic factor expression and production, as well as idNK cell activity in the presence of nitric synthase blocker L-NMMA. Methods: NK cells (CD56⁺) were isolated from the peripheral blood of 15 patients and 15 fertile women on MACS columns and cultured in transformation media containing IL-15, TGF-β, and AZA—a methylation agent—for 7 days in hypoxia (94% N₂, 1% O₂, 5% CO₂). Cultures were set up in four variants: (1) with SC, (2) without SC, (3) with NO, a synthase blocker, and (4) with SC and NO synthase blocker. NK cell activity was determined after 7 days of culturing as CD107a expression after an additional 4h of stimulation with K562 erythroleukemia cells. The expression of the PDE5A, VEGF-A, PIGF, IL-8, and RENBP genes was determined with quantitative real-time PCR (qRT-PCR) using TaqMan probes and ELISA was used to measure the concentrations of VEGF-A, PLGF, IL-8, Ang-I, Ang-II, IFN–γ proteins in culture supernatants after SC supplementation. Results: SC downregulated PDE5A expression and had no effect on other studied angiogenic factors. VEGF-A expression was increased in RPL patients compared with fertile women. Similarly, VEGF production was enhanced in RPL patients’ supernatants and SC increased the concentration of PIGF in culture supernatants. SC did not affect the expression or concentration of other studied factors, nor idNK cell activity, regardless of NO synthase blockade.

Arterial Stiffness as a Cardiovascular Risk Factor for the Development of Preeclampsia and Pharmacopreventive Options

Arterial stiffness (AS) describes the rigidity of the arterial walls. Epidemiological studies have shown that increased AS is an independent predictive marker of cardiovascular (CV) morbidity and mortality in both pregnant and non-pregnant women. Preeclampsia (PE), a form of pregnancy-induced hypertension, affects approximately 5% of pregnancies worldwide. Preeclamptic women have a higher risk of CV disease (CVD), mainly because PE damages the heart's ability to relax between contractions. Different pharmacological approaches for the prevention of PE have been tested in clinical trials (e.g. aspirin, enoxaparin, metformin, pravastatin, and sildenafil citrate). In current clinical practice, only low-dose aspirin is used for PE pharmacoprevention. However, low-dose aspirin does not prevent term PE, which is the most common form of PE. Compromised vascular integrity precedes the onset of PE and therefore, AS assessment may constitute a promising predictive marker of PE. Several non-invasive techniques have been developed to assess AS. Compared with normotensive pregnancies, both carotid-femoral pulse wave velocity (cfPWV) and augmentation index (AIx) are increased in PE. In view of simplicity, reliability, and reproducibility, there is an interest in oscillometric AS measurements in pregnancies complicated by PE.

Evaluation and Management of Suspected Fetal Growth Restriction

Impaired fetal growth owing to placental insufficiency is a major contributor to adverse perinatal outcomes. No intervention is available that improves outcomes by changing the pathophysiologic process. Monitoring in early-onset fetal growth restriction (FGR) focuses on optimizing the timing of iatrogenic preterm delivery using cardiotocography and Doppler ultrasound. In late-onset FGR, identifying the fetus at risk for immediate hypoxia and who benefits from expedited delivery is challenging. It is likely that studies in the next decade will provide evidence how to best integrate different monitoring variables and other prognosticators in risk models that are aimed to optimize individual treatment strategies.

Prelabor and intrapartum Doppler ultrasound to predict fetal compromise

According to current estimates, over 20% of the 4 million neonatal deaths occurring globally every year are related to intrapartum hypoxic complications that happen as a result of uterine contractions against a background of inadequate placental function. Most of such intrapartum complications occur among apparently uncomplicated term pregnancies. Available evidence suggests that current risk-assessment strategies do not adequately identify many of the fetuses vulnerable to periods of intermittent hypoxia that characterize human labor. In this review, we discuss the data available on Doppler ultrasound for the evaluation of placental function before and during labor in appropriately grown fetuses; we also discuss the current strategies for ultrasound-based risk stratification, the physiology of intrapartum compromise, and the potential future treatments to prevent fetal distress in labor and reduce perinatal complications related to birth asphyxia.

Decreased Production of TNF-α and IL-6 Inflammatory Cytokines in Non-Pregnant Idiopathic RPL Women Immunomodulatory Effect of Sildenafil Citrate on the Cellular Response of Idiopathic RPL Women

Sildenafil citrate (SC), a PDE5 inhibitor, a drug for erectile dysfunction (ED) and pulmonary hypertension (PAH), was found to exert a positive effect on pregnancy outcomes when administered intravaginally before conception. In our previous studies, sildenafil increased endometrial thickness and significantly decreased peripheral blood NK cell activity after the intravaginal administration in women with recurrent pregnancy loss (RPL). No data are available to confirm the effect of sildenafil on maternal T cell populations involved in shaping fetal-maternal tolerance and NK cell activity. Thus, the present study aimed to establish if SC influences NKT cells or the axis of Th17/Treg cells and Th1/Th2 cytokine production. Materials and methods: Twenty-one healthy fertile women and twenty-two nonpregnant women with idiopathic RPL were studied. The ELISA method was used to evaluate the production of cytokines, including IL-2, IL-12p40, IL-4, IL-10, IL-6, IL-17, IL-21, TGF-β, TNF-α, and IFN-γ in PBMC culture supernatants before and after supplementation with the physiological concentration of SC. The percentages of NKT (CD56⁺CD3⁺CD44⁺CD161⁺), Treg (CD4⁺CD25⁺FOXP3⁺) and Th17 (CD4⁺CD25⁺IL-17A⁺) cells were determined with flow cytometry method. Results: Unexpectedly, we found that the PBMCs of patients with RPL produced a significantly lower level of inflammatory cytokines (TNF-α and IL-6) and a higher level of anti-inflammatory cytokines (TGF-β and IL-10). SC significantly decreased IL-6, IL-12 and increased TGF-β cytokine concentration in fertile women. In the case of RPL patients’ PBMCs, SC improved the production of TNF-α and IL-10. Conclusions: Lower concentration of proinflammatory cytokines in idiopathic RPL women compared to fertile women might suggest the exhaustion of the immune system. The emphasized production of IL-10 by SC partially explains the previously observed downregulation of NK cell activity in RPL patients. The immunomodulatory effect of the drug might be utilized in anti-inflammatory therapies and help achieve positive pregnancy outcomes in women with reproductive failure due to a Th1/Th2 imbalance.

What are the causes for low birthweight in Japan? A single hospital-based study

Low-birthweight (LBW; <2,500 g) babies are at a higher risk of poor educational achievement, disability, and metabolic diseases than normal-birthweight babies in the future. However, reliable data on factors that contribute to LBW have not been considered previously. Therefore, we aimed to examine the distribution of the causes for LBW. A retrospective review of cases involving 4,224 babies whose mothers underwent perinatal care at Keio University Hospital between 2013 and 2019 was conducted. The LBW incidence was 24% (1,028 babies). Of the 1,028 LBW babies, 231 babies were from multiple pregnancies. Of the 797 singleton LBW babies, 518 (65%) were born preterm. Obstetric complications in women with preterm LBW babies included premature rupture of membrane or labor onset (31%), hypertensive disorders of pregnancy (HDP, 64%), fetal growth restriction (24%), non-reassuring fetal status (14%), and placental previa/vasa previa (8%). Of the 279 term LBW babies, 109 (39%) were small for gestational age. Multiple logistic regression analyses revealed the following factors as LBW risk factors in term neonates: low pre-pregnancy maternal weight, inadequate gestational weight gain, birth at 37 gestational weeks, HDP, anemia during pregnancy, female sex, and neonatal congenital anomalies. HDP was an LBW risk factor not only in preterm births but also in term births. Our results suggest that both modifiable and non-modifiable factors are causes for LBW. It may be appropriate to consider a heterogeneous rather than a simple classification of LBW and to evaluate future health risks based on contributing factors.

Recurrence Risk of Fetal Growth Restriction: Management of Subsequent Pregnancies

Fetal growth restriction (FGR) is a common obstetric complication that predisposes to mortality across the lifespan. Women with a prior pregnancy affected by FGR have a 20% to 30% risk of recurrence, but effective preventive strategies are lacking. Pharmacologic interventions to prevent FGR are lacking. Low-dose aspirin may be somewhat effective, but low-molecular-weight heparin and sildenafil are not. Surveillance in a subsequent pregnancy may consist of serial ultrasonography with timing and frequency determined by the clinical severity in the index pregnancy. Once FGR is diagnosed, the principal management strategy consists of close surveillance and carefully timed delivery.

Differences in the Expression of KIR, ILT Inhibitory Receptors, and VEGF Production in the Induced Decidual NK Cell Cultures of Fertile and RPL Women

RESULTS

KIR2DL1 and ILT-2 expression on idNK cells was higher in healthy women than in RPL patients. Sildenafil enhanced NKG2A expression in RPL patients. VEGF concentration was higher in fertile woman idNK cell cultures. idNK cells were more sensitive for necrosis in RPL than in fertile women. SC did not influence VEGF production or idNK cell apoptosis.

CONCLUSIONS

A combination of hypoxia, IL-15, and AZA promotes the conversion of pbNK into idNK cells CD56+CD16--expressing KIR receptors and produces VEGF. Alterations in KIR2DL1 and ILT-2 expression as well as impaired VEGF production were associated with RPL. SC affects NKG2A expression on RPL idNK cells. SC had no effect on VEGF release or idNK cell apoptosis.

Adaptations of the human placenta to hypoxia: opportunities for interventions in fetal growth restriction

BACKGROUND

The placenta is the functional interface between the mother and the fetus during pregnancy, and a critical determinant of fetal growth and life-long health. In the first trimester, it develops under a low-oxygen environment, which is essential for the conceptus who has little defense against reactive oxygen species produced during oxidative metabolism. However, failure of invasive trophoblasts to sufficiently remodel uterine arteries toward dilated vessels by the end of the first trimester can lead to reduced/intermittent blood flow, persistent hypoxia and oxidative stress in the placenta with consequences for fetal growth. Fetal growth restriction (FGR) is observed in ∼10% of pregnancies and is frequently seen in association with other pregnancy complications, such as preeclampsia (PE). FGR is one of the main challenges for obstetricians and pediatricians, as smaller fetuses have greater perinatal risks of morbidity and mortality and postnatal risks of neurodevelopmental and cardio-metabolic disorders.

OBJECTIVE AND RATIONALE

The aim of this review was to examine the importance of placental responses to changing oxygen environments during abnormal pregnancy in terms of cellular, molecular and functional changes in order to highlight new therapeutic pathways, and to pinpoint approaches aimed at enhancing oxygen supply and/or mitigating oxidative stress in the placenta as a mean of optimizing fetal growth.

SEARCH METHODS

An extensive online search of peer-reviewed articles using PubMed was performed with combinations of search terms including pregnancy, placenta, trophoblast, oxygen, hypoxia, high altitude, FGR and PE (last updated in May 2020).

OUTCOMES

Trophoblast differentiation and placental establishment are governed by oxygen availability/hypoxia in early pregnancy. The placental response to late gestational hypoxia includes changes in syncytialization, mitochondrial functions, endoplasmic reticulum stress, hormone production, nutrient handling and angiogenic factor secretion. The nature of these changes depends on the extent of hypoxia, with some responses appearing adaptive and others appearing detrimental to the placental support of fetal growth. Emerging approaches that aim to increase placental oxygen supply and/or reduce the impacts of excessive oxidative stress are promising for their potential to prevent/treat FGR.

WIDER IMPLICATIONS

There are many risks and challenges of intervening during pregnancy that must be considered. The establishment of human trophoblast stem cell lines and organoids will allow further mechanistic studies of the effects of hypoxia and may lead to advanced screening of drugs for use in pregnancies complicated by placental insufficiency/hypoxia. Since no treatments are currently available, a better understanding of placental adaptations to hypoxia would help to develop therapies or repurpose drugs to optimize placental function and fetal growth, with life-long benefits to human health.

Novel approaches to combat preeclampsia: from new drugs to innovative delivery

Preeclampsia is a complex disease affecting 2-8% of pregnancies worldwide. It poses significant risk of maternal and perinatal morbidity and mortality. Despite the rising research interest to discover new therapeutic approaches to prevent and treat preeclampsia, options remain limited. Identifying the important pathological stages in the progression of this disease allows us to evaluate effective candidate therapeutics. Three important stages in the pathophysiology are: 1) placental hypoxia and oxidative stress, 2) excess release of anti-angiogenic and pro-inflammatory factors, and 3) widespread systemic endothelial dysfunction and vasoconstriction. Repurposing drugs already safe for use in pregnancy is an attractive option for discovery of novel therapeutics. There are many drugs currently being assessed to treat preeclampsia, including proton pump inhibitors (PPIs), metformin, statins, sulfasalazine, sofalcone, resveratrol, melatonin, and sildenafil citrate. These drugs show positive effects in preclinical studies, targeting placental and endothelial dysfunction. However, using novel therapeutics can raise safety concerns for the developing fetus. Therefore, innovative targeted delivery systems are being developed to safely administer these therapeutics directly to the placenta and/or endothelium. These include nanoparticle delivery systems, developed and used by the oncology field, now being adapted for obstetrics. This technology is currently being assessed in animal models and shows promise for treating preeclampsia. Combining effective therapeutics with targeted drug delivery could be the future of preeclampsia treatment.

Prenatal Amino Acid Supplementation to Improve Fetal Growth: A Systematic Review and Meta-Analysis

Aberrant fetal growth remains a leading cause of perinatal morbidity and mortality and is associated with a risk of developing non-communicable diseases later in life. We performed a systematic review and meta-analysis combining human and animal studies to assess whether prenatal amino acid (AA) supplementation could be a promising approach to promote healthy fetal growth. PubMed, Embase, and Cochrane libraries were searched to identify studies orally supplementing the following AA groups during gestation: (1) arginine family, (2) branched chain (BCAA), and (3) methyl donors. The primary outcome was fetal/birth weight. Twenty-two human and 89 animal studies were included in the systematic review. The arginine family and, especially, arginine itself were studied the most. Our meta-analysis showed beneficial effects of arginine and (N-Carbamyl) glutamate (NCG) but not aspartic acid and citrulline on fetal/birth weight. However, no effects were reported when an isonitrogenous control diet was included. BCAA and methyl donor supplementation did not affect fetal/birth weight. Arginine family supplementation, in particular arginine and NCG, improves fetal growth in complicated pregnancies. BCAA and methyl donor supplementation do not seem to be as promising in targeting fetal growth. Well-controlled research in complicated pregnancies is needed before ruling out AA supplements or preferring arginine above other AAs.

Type 5 phosphodiesterase (PDE5) and the vascular tree: From embryogenesis to aging and disease

•

Vascular development depends on the timely differentiation of endothelial and smooth muscle cells.

•

Vascular aging and vascular disease are influenced by endothelial and vascular smooth muscle cell compartments.

•

A survey of the literature on the role of PDE5 in vascular development, aging and disease is reported.

•

The role of PDE5 on vascular development, aging and disease needs to be further investigated by its genetic ablation.

Vascular tree development depends on the timely differentiation of endothelial and vascular smooth muscle cells. These latter are key players in the formation of the vascular scaffold that offers resistance to the blood flow. This review aims at providing an overview on the role of PDE5, the cGMP-specific phosphodiesterase that historically attracted much attention for its involvement in male impotence, in the regulation of vascular smooth muscle cell function. The overall goal is to underscore the importance of PDE5 expression and activity in this cell type in the context of the organs where its function has been extensively studied.

Hydroxychloroquine as a Preventive and Therapeutic Option in Preeclampsia - a Literature Review

Preeclampsia is one of the most feared complications of pregnancy and puerperium and represents a serious threat to mother and child. In addition, a history of preeclampsia increases the risk of future cardiovascular events. New diagnostic and therapeutic approaches are needed. New therapeutic options are currently being discussed, one of which is the administration of hydroxychloroquine. It is an antimalarial drug which is also used to treat rheumatological disease and its use in pregnancy is considered safe. A reduced incidence of preeclampsia in patients with selected rheumatological disorders after administration of hydroxychloroquine has already been shown; however, the case numbers are very low. Neither the full pathogenesis of preeclampsia nor the exact modes of action of hydroxychloroquine have been completely elucidated, but there are several common features which make hydroxychloroquine a promising option for the prevention and treatment of preeclampsia. Further research, especially prospective, randomized controlled trials, is needed to prove its efficacy. This review discusses the pathogenesis of preeclampsia and gives an overview of new options for its prevention and treatment, including the administration of hydroxychloroquine in pregnancy.

Preeclampsia beyond pregnancy: long-term consequences for mother and child

Preeclampsia is defined as new-onset hypertension after the 20th wk of gestation along with evidence of maternal organ failure. Rates of preeclampsia have steadily increased over the past 30 yr, affecting ∼4% of pregnancies in the United States and causing a high economic burden (22, 69). The pathogenesis is multifactorial, with acknowledged contributions by placental, vascular, renal, and immunological dysfunction. Treatment is limited, commonly using symptomatic management and/or early delivery of the fetus (6). Along with significant peripartum morbidity and mortality, current research continues to demonstrate that the consequences of preeclampsia extend far beyond preterm delivery. It has lasting effects for both mother and child, resulting in increased susceptibility to hypertension and chronic kidney disease (45, 54, 115, 116), yielding lifelong risk to both individuals. This review discusses recent guideline updates and recommendations along with current research on these long-term consequences of preeclampsia.

Maternal Sildenafil vs Placebo in Pregnant Women With Severe Early-Onset Fetal Growth Restriction: A Randomized Clinical Trial

Importance

Severe early onset fetal growth restriction caused by placental dysfunction leads to high rates of perinatal mortality and neonatal morbidity. The phosphodiesterase 5 inhibitor, sildenafil, inhibits cyclic guanosine monophosphate hydrolysis, thereby activating the effects of nitric oxide, and might improve uteroplacental function and subsequent perinatal outcomes.

Objective

To determine whether sildenafil reduces perinatal mortality or major morbidity.

Design, Setting, and Participants

This placebo-controlled randomized clinical trial was conducted at 10 tertiary referral centers and 1 general hospital in the Netherlands from January 20, 2015, to July 16, 2018. Participants included pregnant women between 20 and 30 weeks of gestation with severe fetal growth restriction, defined as fetal abdominal circumference below the third percentile or estimated fetal weight below the fifth percentile combined with Dopplers measurements outside reference ranges or a maternal hypertensive disorder. The trial was stopped early owing to safety concerns on July 19, 2018, whereas benefit on the primary outcome was unlikely. Data were analyzed from January 20, 2015, to January 18, 2019. The prespecified primary analysis was an intention-to-treat analysis including all randomized participants.

Interventions

Participants were randomized to sildenafil, 25 mg, 3 times a day vs placebo.

Main Outcomes and Measures

The primary outcome was a composite of perinatal mortality or major neonatal morbidity until hospital discharge.

Results

Out of 360 planned participants, a total of 216 pregnant women were included, with 108 women randomized to sildenafil (median gestational age at randomization, 24 weeks 5 days [interquartile range, 23 weeks 3 days to 25 weeks 5 days]; mean [SD] estimated fetal weight, 458 [160] g) and 108 women randomized to placebo (median gestational age, 25 weeks 0 days [interquartile range, 22 weeks 5 days to 26 weeks 3 days]; mean [SD] estimated fetal weight, 464 [186] g). In July 2018, the trial was halted owing to concerns that sildenafil may cause neonatal pulmonary hypertension, whereas benefit on the primary outcome was unlikely. The primary outcome, perinatal mortality or major neonatal morbidity, occurred in the offspring of 65 participants (60.2%) allocated to sildenafil vs 58 participants (54.2%) allocated to placebo (relative risk, 1.11; 95% CI, 0.88-1.40; P = .38). Pulmonary hypertension, a predefined outcome important for monitoring safety, occurred in 16 neonates (18.8%) in the sildenafil group vs 4 neonates (5.1%) in the placebo group (relative risk, 3.67; 95% CI, 1.28-10.51; P = .008).

Conclusions and Relevance

These findings suggest that antenatal maternal sildenafil administration for severe early onset fetal growth restriction did not reduce the risk of perinatal mortality or major neonatal morbidity. The results suggest that sildenafil may increase the risk of neonatal pulmonary hypertension.

Trial Registration

ClinicalTrials.gov Identifier: NCT02277132.

Effect of sildenafil on maternal hemodynamics in pregnancies complicated by severe early-onset fetal growth restriction: planned subgroup analysis from a multicenter randomized placebo-controlled double-blind trial

OBJECTIVES

Fetal growth restriction (FGR) is associated with maternal cardiovascular changes. Sildenafil, a phosphodiesterase type-5 inhibitor, potentiates the actions of nitric oxide, and it has been suggested that it alters maternal hemodynamics, potentially improving placental perfusion. Recently, the Dutch STRIDER trial was stopped prematurely owing to excess neonatal mortality secondary to pulmonary hypertension. The main aim of this study was to investigate the effect of sildenafil on maternal hemodynamics in pregnancies with severe early-onset FGR.

METHODS

This was a cardiovascular substudy within a UK multicenter, placebo-controlled trial, in which 135 women with a singleton pregnancy and severe early-onset FGR (defined as a combination of estimated fetal weight or abdominal circumference below the 10^th centile and absent/reversed end-diastolic flow in the umbilical artery on Doppler velocimetry, diagnosed between 22 + 0 and 29 + 6 weeks' gestation) were assigned randomly to receive either 25 mg sildenafil three times daily or placebo until 32 + 0 weeks' gestation or delivery. Maternal blood pressure (BP), heart rate (HR), augmentation index, pulse wave velocity (PWV), cardiac output, stroke volume (SV) and total peripheral resistance were recorded before randomization, 1-2 h and 48-72 h post-randomization, and 24-48 h postnatally. For continuous data, analysis was performed using repeated measures ANOVA methods including terms for timepoint, treatment allocation and their interaction.

RESULTS

Included were 134 women assigned randomly to sildenafil (n = 69) or placebo (n = 65) who had maternal BP and HR recorded at baseline. At 1-2 h post-randomization, compared with baseline values, sildenafil increased maternal HR by 4 bpm more than did placebo (mean difference, 5.00 bpm (95% CI, 1.00-12.00 bpm) vs 1.25 bpm (95% CI, -5.38 to 7.88 bpm); P = 0.004) and reduced systolic BP by 1 mmHg more (mean difference, -4.13 mmHg (95% CI, -9.94 to 1.44 mmHg) vs -2.75 mmHg (95% CI, -7.50 to 5.25 mmHg); P = 0.048). Even after adjusting for maternal mean arterial pressure, sildenafil reduced aortic PWV by 0.60 m/s more than did placebo (mean difference, -0.90 m/s (95% CI, -1.31 to -0.51 m/s) vs -0.26 m/s (95% CI, -0.75 to 0.59 m/s); P = 0.001). Sildenafil was associated with a non-significantly greater decrease in SV index after 1-2 h post-randomization than was placebo (mean difference, -5.50 mL/m² (95% CI, -11.00 to -0.50 mL/m² ) vs 0.00 mL/m² (95% CI, -5.00 to 4.00 mL/m² ); P = 0.056).

CONCLUSIONS

Sildenafil in a dose of 25 mg three times daily increases HR, reduces BP and reduces arterial stiffness in pregnancies complicated by severe early-onset FGR. These changes are short term, modest and consistent with the anticipated vasodilatory effect. They have no short- or long-term clinical impact on the mother. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Prenatal Use of Sildenafil in Fetal Growth Restriction and Its Effect on Neonatal Tissue Oxygenation-A Retrospective Analysis of Hemodynamic Data From Participants of the Dutch STRIDER Trial

Objective: Sildenafil is under investigation as a potential agent to improve uteroplacental perfusion in fetal growth restriction (FGR). However, the STRIDER RCT was halted after interim analysis due to futility and higher rates of persistent pulmonary hypertension and mortality in sildenafil-exposed neonates. This hypothesis-generating study within the Dutch STRIDER trial sought to understand what happened to these neonates by studying their regional tissue oxygen saturation (rSO₂) within the first 72 h after birth. Methods: Pregnant women with FGR received 25 mg placebo or sildenafil thrice daily within the Dutch STRIDER trial. We retrospectively analyzed the cerebral and renal rSO₂ monitored with near-infrared spectroscopy (NIRS) in a subset of neonates admitted to two participating neonatal intensive care units, in which NIRS is part of standard care. Secondarily, blood pressure and heart rate were analyzed to aid interpretation. Differences in oxygenation levels and interaction with time (slope) between placebo- and sildenafil-exposed groups were tested using mixed effects analyses with multiple comparisons tests. Results: Cerebral rSO₂ levels were not different between treatment groups (79 vs. 77%; both n = 14) with comparable slopes. Sildenafil-exposed infants (n = 5) showed lower renal rSO₂ than placebo-exposed infants (n = 6) during several time intervals on day one and two. At 69-72 h, however, the sildenafil group showed higher renal rSO₂ than the placebo group. Initially, diastolic blood pressure was higher and heart rate lower in the sildenafil than the placebo group, which changed during day two. Conclusions: Although limited by sample size, our data suggest that prenatal sildenafil alters renal but not cerebral oxygenation in FGR neonates during the first 72 post-natal hours. The observed changes in renal oxygenation could reflect a vasoconstrictive rebound from sildenafil. Similar changes observed in accompanying vital parameters support this hypothesis.

Maternal administration of tadalafil improves fetal ventricular systolic function in a Hey2 knockout mouse model of fetal heart failure

BACKGROUND

There is no established transplacental treatment for heart failure (HF) in utero, and no animal models or experimental systems of fetal HF have been established. This study aimed to investigate the effect of maternal tadalafil administration on fetal cardiovascular function and uteroplacental circulation in a murine model of fetal HF.

METHODS AND RESULTS

We first used an ultra-high-frequency ultrasound imaging system in utero and demonstrated that Hey2^-/- embryos had worsening right ventricular hypoplasia and marked left ventricular (LV) dilatation as gestation progressed. In both ventricles, fractional shortening (FS) and the E/A ratio were significantly lower in Hey2^-/- embryos than in wild-type embryos, indicating that the embryos can be used as a murine model of fetal HF. Subsequently, we evaluated the effect of tadalafil treatment (0.04 or 0.08 mg/ml; T0.04 or T0.08 groups, respectively) on fetoplacental circulation in Hey2^-/- embryos. LV FS was significantly higher in the T0.04 group than in control (P < 0.01), whereas LV dilation, mitral E/A ratio, and umbilical artery resistance index were not significantly different among all groups. The thinness of the LV compacted layer did not differ between the T0.04 and vehicle-treated Hey2^-/- embryos.

CONCLUSIONS

A phenotype comprising marked dilatation and reduced FS of the left ventricles was identified in Hey2^-/- embryos, suggesting these embryos as a murine model of fetal HF. In addition, maternal administration of tadalafil improved LV systolic function without altering LV morphological abnormalities in Hey2^-/- embryos. Our findings suggest that tadalafil is a potential agent to treat impaired fetal ventricular systolic function.

Therapeutic targeting of 3',5'-cyclic nucleotide phosphodiesterases: inhibition and beyond

Phosphodiesterases (PDEs), enzymes that degrade 3',5'-cyclic nucleotides, are being pursued as therapeutic targets for several diseases, including those affecting the nervous system, the cardiovascular system, fertility, immunity, cancer and metabolism. Clinical development programmes have focused exclusively on catalytic inhibition, which continues to be a strong focus of ongoing drug discovery efforts. However, emerging evidence supports novel strategies to therapeutically target PDE function, including enhancing catalytic activity, normalizing altered compartmentalization and modulating post-translational modifications, as well as the potential use of PDEs as disease biomarkers. Importantly, a more refined appreciation of the intramolecular mechanisms regulating PDE function and trafficking is emerging, making these pioneering drug discovery efforts tractable.

Perspective: L-arginine and L-citrulline Supplementation in Pregnancy: A Potential Strategy to Improve Birth Outcomes in Low-Resource Settings

The available data support the hypothesis that L-arginine or L-citrulline supplementation would be suitable for implementation in resource-constrained settings and will enhance placental vascular development and improve birth outcomes. In resource-constrained settings, the rates of adverse birth outcomes, including fetal growth restriction, preterm birth, and low birth weight, are disproportionately high. Complications resulting from preterm birth are now the leading cause of mortality in children <5 y of age worldwide. Despite the global health burden of adverse birth outcomes, few effective interventions are currently available and new strategies are urgently needed, especially for low-resource settings. L-arginine is a nutritionally essential amino acid in pregnancy and an immediate precursor of nitric oxide. During pregnancy, placental and embryonic growth increases the demand for L-arginine, which can exceed endogenous synthesis of L-arginine from L-citrulline, necessitating increased dietary intake. In many low-resource settings, dietary intake of L-arginine in pregnancy is inadequate owing to widespread protein malnutrition and depletion of endogenous L-arginine due to maternal infections, in particular malaria. Here we examine the role of the L-arginine-nitric oxide biosynthetic pathway in pregnancy including placental vascular development and fetal growth. We review the evidence for the relations between altered L-arginine bioavailability and pregnancy outcomes, and strategies for arginine supplementation in pregnancy. Existing studies of L-arginine supplementation in pregnancy in high-resource settings have shown improved maternal and fetal hemodynamics, prevention of pre-eclampsia, and improved birth outcomes including higher birth weight and longer gestation. Arginine supplementation studies now need to be extended to pregnant women in low-resource settings, especially those at risk of malaria.

The effects of sildenafil in maternal and fetal outcomes in pregnancy: A systematic review and meta-analysis

BACKGROUND

The number of studies associating the use of sildenafil in gestation is increasing. This drug inhibits phosphodiesterase type 5 (PDE5), an enzyme responsible for degradation of nitric oxide, and its efficacy is greater in the placental territory, as the maternal side of the placenta have more PDE5 than other sites. For this reason, promising results have been observed related to the prevention of preeclampsia and intrauterine growth restriction and to improvement of maternal-fetal morbidity in cases of placental insufficiency.

OBJECTIVE

To evaluate the benefits of using sildenafil in pregnancy.

SEARCHED STRATEGY

MEDLINE, ClinicalTrials.gov, Embase, LILACS and Cochrane databases were searched through September 2018. There was no restriction in language or year of publication. This study was registered in PROSPERO (CRD42017060288).

SELECTION CRITERIA

Randomized clinical trials which used sildenafil for treatment or prevention of obstetric diseases compared with placebo were selected.

DATA COLLECTION AND ANALYSIS

The results were obtained using the inverse variance method for continuous variables and Man-Whitney for categorical variables.

MAIN RESULTS

Among a population of 598 pregnant women from the seven clinical trials included, 139 had pre-eclampsia, 275 had intrauterine growth restriction, and 184 had oligohydramnios. A significant increase of 222.58 grams [27.75 to 417.41] was observed in the fetal weight at birth of patients taking sildenafil. The other outcomes did not show any statistical significance. This may be due to the small number of patients used in each study and the great heterogeneity between the groups.

CONCLUSIONS

Sildenafil could be associated with increasing fetal weight at birth in placental insufficiency despite the limitations of this meta-analysis, even though more studies in this field are needed to introduce this drug into obstetric clinical practice.

Low Birth Weight, Blood Pressure and Renal Susceptibility

PURPOSE OF THE REVIEW

The purpose of this review is to highlight the clinical significance of increased renal risk that has its origins in fetal life. This review will also discuss the critical need to identify therapeutic interventions for use in a pregnancy complicated by placental dysfunction and intrauterine growth restriction that can mitigate the developmental origins of kidney disease without inflicting additional harm on the developing fetus.

RECENT FINDINGS

A reduction in nephron number is a contributory factor in the pathogenesis of hypertension and kidney disease in low birth weight individuals. Reduced nephron number may heighten susceptibility to a secondary renal insult, and recent studies suggest that perinatal history including birth weight should be considered in the assessment of renal risk in kidney donors. This review highlights current findings related to placental dysfunction, intrauterine growth restriction, increased risk for renal injury and disease, and potential therapeutic interventions.

Placental effects and transfer of sildenafil in healthy and preeclamptic conditions

Background

The phosphodiesterase-5 inhibitor (PDE5) sildenafil has emerged as a promising treatment for preeclampsia (PE). However, a sildenafil trial was recently halted due to lack of effect and increased neonatal morbidity.

Methods

Ex vivo dual-sided perfusion of an isolated cotyledon and wire-myography on chorionic plate arteries were performed to study the effects of sildenafil and the non-selective PDE inhibitor vinpocetine on the response to the NO donor sodium nitroprusside (SNP) under healthy and PE conditions. Ex vivo perfusion was also used to study placental transfer of sildenafil in 6 healthy and 2 PE placentas. Furthermore, placental mRNA and protein levels of eNOS, iNOS, PDE5 and PDE1 were quantified.

Findings

Sildenafil and vinpocetine significantly enhanced SNP responses in chorionic plate arteries of healthy, but not PE placentas. Only sildenafil acutely decreased baseline tension in arteries of both healthy and PE placentas. At steady state, the foetal-to-maternal transfer ratio of sildenafil was 0·37 ± 0·03 in healthy placentas versus 0·66 and 0·47 in the 2 PE placentas. mRNA and protein levels of PDE5, eNOS and iNOS were comparable in both groups, while PDE1 levels were lower in PE.

Interpretation

The absence of sildenafil-induced NO potentiation in arteries of PE placentas, combined with the non-PDE-mediated effects of sildenafil and the lack of PDE5 upregulation in PE, argue against sildenafil as the preferred drug of use in PE. Moreover, increased placental transfer of sildenafil in PE might underlie the neonatal morbidity in the STRIDER trial.

Fund

This study was funded by an mRACE Erasmus MC grant.

Prenatal Sildenafil Therapy Improves Cardiovascular Function in Fetal Growth Restricted Offspring of Dahl Salt-Sensitive Rats

Fetal growth restriction (FGR) is associated with increased risk for cardiovascular and renal disorders in later life. Prenatal sildenafil improves birth weight in FGR animal models. Whether sildenafil treatment protects against long-term cardiovascular and renal disease in these offspring is unknown. The aim of this study is to test the hypothesis that prenatal sildenafil ameliorates cardiovascular and renal function in FGR offspring of Dahl salt-sensitive rats. Sildenafil citrate (60 mg/kg per day) or control gel diet (containing 0.3% salt) was administered from gestational day ten until birth. In male and female offspring, the mean arterial pressure was measured by telemetry in 1 subset from week 5 until week twenty. Echocardiographic parameters, glomerular filtration rate, and fractional electrolyte excretion were determined in another subset at week 9. Aortic and mesenteric artery rings were prepared to assess endothelial-dependent (acetylcholine) and -independent (sodium nitroprusside) vasorelaxation (week 10). The rise in mean arterial pressure per week was attenuated in treated versus untreated male offspring. Mesenteric arteries showed an increased endothelium-dependent relaxation and improved endothelium-independent relaxation in treated versus control male offspring. No differences in aortic relaxation, echocardiographic parameters or renal function were observed between groups. Prenatal sildenafil treatment subtly improves cardiovascular but not renal function in the offspring of this FGR rat model. Translationally, in utero treatment could be beneficial for cardiovascular programming in a sex-specific manner; however, caution is warranted since recent human trials have been halted because of potentially deleterious neonatal side effects when treating pregnancies complicated with severe FGR with sildenafil.

Pre-eclampsia: pathogenesis, novel diagnostics and therapies

Pre-eclampsia is a complication of pregnancy that is associated with substantial maternal and fetal morbidity and mortality. The disease presents with new-onset hypertension and often proteinuria in the mother, which can progress to multi-organ dysfunction, including hepatic, renal and cerebral disease, if the fetus and placenta are not delivered. Maternal endothelial dysfunction due to circulating factors of fetal origin from the placenta is a hallmark of pre-eclampsia. Risk factors for the disease include maternal comorbidities, such as chronic kidney disease, hypertension and obesity; a family history of pre-eclampsia, nulliparity or multiple pregnancies; and previous pre-eclampsia or intrauterine fetal growth restriction. In the past decade, the discovery and characterization of novel antiangiogenic pathways have been particularly impactful both in increasing understanding of the disease pathophysiology and in directing predictive and therapeutic efforts. In this Review, we discuss the pathogenic role of antiangiogenic proteins released by the placenta in the development of pre-eclampsia and review novel therapeutic strategies directed at restoring the angiogenic imbalance observed during pre-eclampsia. We also highlight other notable advances in the field, including the identification of long-term maternal and fetal risks conferred by pre-eclampsia.

Placental Origins of Preeclampsia: Potential Therapeutic Targets

Preeclampsia (PE) remains a leading cause of maternal and perinatal morbidity and mortality in obstetrics worldwide. No effective treatments to reduce its incidence and severity in clinical practice are currently available. A variety of hypotheses have been generated aiming to explain the origins of PE, notably being the genetic predispositions and placental dysfunction. As regard to placental dysfunction, much progress has been made in basic research and several potential therapeutic targets have been identified. This review will discuss in detail the potential therapeutic targets in PE models including uteroplacental blood flow, oxidative stress, vasoactive factors and inflammation/immune response, and introduce the evolving technologies for placental research nowadays.

[Potential value of placental angiogenic factors as biomarkers in preeclampsia for clinical physicians]

The role of angiogenic factors in the onset of clinical manifestations of preeclampsia was demonstrated in 2003 by the implication of sFlt-1, PlGF and VEGF, and in 2006 by the implication of soluble endoglin. Placental ischemia and inflammation observed in preeclampsia alter both the production and progression of angiogenic factors during pregnancy. During the first trimester, the combination of PlGF with clinical, biophysical and biological factors results in a better test than the conventional one. However, the clinical value of this method remains to be confirmed. During the second and third trimesters, the sFlt-1/PlGF ratio may be used, with or without pre-existing renal disease, for short-term prediction, diagnosis, and prognosis, and to evaluate the effectiveness of preeclampsia treatment. While a sFlt-1/PlGF ratio<38 and≤33, respectively, rules out the short-term onset and diagnosis of preeclampsia, a sFlt-1/PlGF ratio≥85 between 20 and 34 weeks of pregnancy and≥110 beyond 34 weeks of pregnancy confirms a diagnosis of preeclampsia. Angiogenic and non-angiogenic preeclampsia are identified by a sFlt-1PlGF≥85 and<85, respectively, with the risk of maternal and fetal complications at two weeks differing between the two. Similarly, a sFlt-1/PlGF ratio>665 and>205, respectively, is a good short-term predictor of adverse outcomes of early and late-onset preeclampsia. These values could be incorporated into future guidelines for better clinical management of preeclampsia.

STRIDER NZAus: a multicentre randomised controlled trial of sildenafil therapy in early-onset fetal growth restriction

OBJECTIVE

To assess the effect of maternal sildenafil therapy on fetal growth in pregnancies with early-onset fetal growth restriction.

DESIGN

A randomised placebo-controlled trial.

SETTING

Thirteen maternal-fetal medicine units across New Zealand and Australia.

POPULATION

Women with singleton pregnancies affected by fetal growth restriction at 22⁺⁰ to 29⁺⁶ weeks.

METHODS

Women were randomised to oral administration of 25 mg sildenafil citrate or visually matching placebo three times daily until 32⁺⁰ weeks, birth or fetal death (whichever occurred first).

MAIN OUTCOME MEASURES

The primary outcome was the proportion of pregnancies with an increase in fetal growth velocity. Secondary outcomes included live birth, survival to hospital discharge free of major neonatal morbidity and pre-eclampsia.

RESULTS

Sildenafil did not affect the proportion of pregnancies with an increase in fetal growth velocity; 32/61 (52.5%) sildenafil-treated, 39/57 (68.4%) placebo-treated [adjusted odds ratio (OR) 0.49, 95% CI 0.23-1.05] and had no effect on abdominal circumference Z-scores (P = 0.61). Sildenafil use was associated with a lower mean uterine artery pulsatility index after 48 hours of treatment (1.56 versus 1.81; P = 0.02). The live birth rate was 56/63 (88.9%) for sildenafil-treated and 47/59 (79.7%) for placebo-treated (adjusted OR 2.50, 95% CI 0.80-7.79); survival to hospital discharge free of major neonatal morbidity was 42/63 (66.7%) for sildenafil-treated and 33/59 (55.9%) for placebo-treated (adjusted OR 1.93, 95% CI 0.84-4.45); and new-onset pre-eclampsia was 9/51 (17.7%) for sildenafil-treated and 14/55 (25.5%) for placebo-treated (OR 0.67, 95% CI 0.26-1.75).

CONCLUSIONS

Maternal sildenafil use had no effect on fetal growth velocity. Prospectively planned meta-analyses will determine whether sildenafil exerts other effects on maternal and fetal/neonatal wellbeing.

TWEETABLE ABSTRACT

Maternal sildenafil use has no beneficial effect on growth in early-onset FGR, but also no evidence of harm.

Vascular changes in fetal growth restriction: clinical relevance and future therapeutics

Fetal growth restriction (FGR) affects about 5-10% pregnancies and is associated with poorer outcomes in the perinatal period. Additionally, long standing epidemiological data support its association with chronic diseases such as hypertension and diabetes. Cardiac and vascular adaptations in response to chronic hypoxemia due to utero-placental insufficiency are hallmarks of fetal adaptations. Investigators have attempted to identify these changes in the placenta at the microscopic and molecular level. The ex vivo dual perfusion model of the placenta enables the study of placental haemodynamics in growth-restricted pregnancies. Persistent arterial abnormalities (thickness and stiffness) noted on vascular ultrasound during fetal life through to the young-adult age group for those affected by FGR, seem to be a plausible link between in utero events and chronic circulatory diseases. Using these, this review reflects current thought on vascular maladaptive changes in the FGR cohorts and the role in investigating current and future therapeutics.