Reducing the risk of fetal distress with sildenafil study (RIDSTRESS): a double-blind randomised control trial

Dose Sildenafil Citrate Reduce the Incidence of Emergency Cesarean Section and Fetal Distress During Labor? A Randomized Double-Blinded Clinical Trial

Background

Fetal distress (FD) is one of the most frequent causes of emergency cesarean section (CS) due to the insufficient uteroplacental blood supply during labor. There is a theory that Sildenafil citrate (SC) may improve the uteroplacental blood supply and decrease fetal hypoxia and FD.

Methods

In a randomized double-blinded clinical trial, a total of 208 low-risk subjects who met our stringent inclusion criteria were randomly assigned into two groups: the Sildenafil citrate group (n=104) and the placebo group (n=104). These participants were referred to our referral gynecology and obstetrics department for delivery between July 2022 to September 2022. The SC group received oral SC at a dose of 50 mg every 6 hr, up to a maximum of three times. The final maternal-fetal-neonatal results were recorded and all data were analyzed using SPSS version 23.

Results

The mean age of mothers was 28.98±5.6 years and 120 cases were primigravid (57.7%). Out of a total of 208 pregnant subjects, 168 subjects delivered through normal vaginal delivery (80.8%) and 40 cases underwent emergency CS (19.2%). The number of NVD in Sildenafil group was significantly more than placebo group (87.5% vs. 74%) and SC decreased the rate of emergency CS to 87.5% (RR=2.46%, 95%CI 1.19-5.08). Also, SC decreased the rate of FD to 53.8% (RR=2.83%, 95%CI of 1-8.24).

Conclusion

The results showed that SC can effectively decrease the rate of emergency CS and FD during labor.

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.

Analysis of Factors Associated With Variability and Acidosis of the Umbilical Artery pH at Birth

Background: Perinatal asphyxia is a significant contributing factor for neonatal morbidity and mortality. The aim of this study was to investigate the clinical factors associated with umbilical artery pH variability and fetal acidosis at birth. Methods: This is a single center cross-sectional study in a public regional hospital in southeastern Spain from January to December 2019. The reference population was 1.655 newborns, final sample of 312 experimental units with validated values of umbilical cord blood pH. Results: Factors such as gestational age at term ( X ¯ at - term : 7.26 ± 0.08- X ¯ no -_at-term: 7.31 ± 0.05, p: 0.00), primiparity ( X ¯ primiparity : 7.24 ± 0.078- X ¯ multiparity : 7.27 ± 0.08, p: 0.01), induced labor ( X ¯ induced : 7.24 ± 0.07- X ¯ spontaneous : 7.26 ± 0.081, p: 0.02), vaginal delivery ( X ¯ vaginal :7.25 ± 0.08- X ¯ cesarean :7.27 ± 0.07, p: 0.01), and prolonged dilation duration ( X ¯ AboveAverage : 7.22 ± 0.07- X ¯ BelowAverage : 7.27 ± 0.08, p: 0.00), expulsion duration ( X ¯ AboveAverage : 7.23 ± 0.07- X ¯ BelowAverage : 7.26 ± 0.08, p: 0.01), and total labor duration ( X ¯ AboveAverage : 7.23 ± 0.07- X ¯ BelowAverage : 7.27 ± 0.08, p: 0.00) are associated with a decrease in umbilical artery pH at birth. However, only three factors are associated with acidosis pH (<7.20) of the umbilical artery at birth: the induction of labor [OR: 1.74 (95% CI: 0.98-3.10); p: 0.04], vaginal delivery [OR: 2.09 (95% CI: 0.95-4.61); p: 0.04], and total duration of labor [OR: 2.06 (95% CI: 1.18-3.57); p: 0.01]. Conclusions: Although several factors may affect the variability of umbilical artery pH at birth by decreasing their mean values (gestational age, primiparity, induced labor, vaginal delivery and prolonged: dilation duration, expulsion duration and total labor duration), only induction of labor, vaginal delivery and total duration of labor are associated with an acidosis (<7.20) of same.

Changes in fetoplacental Doppler indices following intrapartum maternal sildenafil citrate treatment

OBJECTIVE

Uterine contractions during labour can result in a 60 % decline in fetoplacental perfusion, predisposing the fetus to hypoxic brain injury. Sildenafil citrate (SC) has shown promise in increasing uteroplacental perfusion as well as reducing the risk of operative birth for intrapartum fetal compromise (IFC). The aim of this study was to investigate the effect of intrapartum SC administration on fetoplacental blood flow indices.

METHODS

This was a subgroup analysis from an earlier Phase II double blind randomized controlled trial; assessing the effect of intrapartum SC administration (50 mg orally 8 -hly in labour) compared to placebo for the reduction of operative birth for IFC. An ultrasound scan measuring fetoplacental Doppler indices was performed prior to and 1-4 h after the administration of the first treatment dose.

RESULTS

Of the 300 women randomized to the main study, pre-treatment ultrasound scans were performed in 261 participants who received the study medication; paired pre- and post-treatment scans were performed in 70 (26.8 %). SC resulted in an increase in the middle cerebral artery pulsatility index (PI) z-score [+0.08 (1.35) vs.-0.12 (1.15)], a decline in the umbilical artery-PI z-score [-0.07 (0.96) vs. + 0.04 (1.25)] and an increase in the cerebroplacental ratio [MCA-PI/UA-PI] (CPR) z-score [+0.10 (1.13) vs.-0.26 (1.14)] although these failed to reach statistical significance. Amongst those with a pre-treatment CPR above the 5th centile, SC significantly reduced the risk of operative birth for IFC compared to placebo [logrank p = 0.02; hazards ratio 0.48, 95 % CI 0.29-0.77, p = 0.003].

CONCLUSION

Although the differences in Doppler indices pre- and post- SC treatment were non-significant, there was a clear trend towards a reduction in the UA PI, a corresponding increase in the MCA PI and a rise in post treatment CPR values suggesting potential improvement in fetoplacental Dopplers with intrapartum SC treatment. However this study was limited by the small sample size. The results of this hypothesis generating study suggest that it may be possible to stratify women that would most benefit from this intervention based upon their pre-labour CPR.

Safety and efficacy of sildenafil citrate to reduce operative birth for intrapartum fetal compromise at term: a phase 2 randomized controlled trial

BACKGROUND AND OBJECTIVE

Sildenafil citrate is a vasodilator used in erectile dysfunction and pulmonary hypertension. We tested whether it reduces emergency operative births for fetal compromise and improves fetal or uteroplacental perfusion in labor in a phase 2 double-blind randomized controlled trial.

STUDY DESIGN

Women at term in early labor or undergoing scheduled induction of labor at Mater Mother's Hospital, Brisbane, Australia, were randomly allocated 50 mg of sildenafil citrate orally 8 hourly up to 150 mg or placebo. Intrapartum fetal monitoring followed Royal Australian and New Zealand College of Obstetricians and Gynaecologists guidelines. Primary outcomes were (1) emergency operative birth (by cesarean delivery or instrumental vaginal birth) for intrapartum fetal compromise and (2) mean indices of fetal and uteroplacental perfusion using Doppler ultrasound. Analysis was by intention-to-treat.

TRIAL REGISTRATION NUMBER

ANZCTRN12615000319572 RESULTS: Between September 2015 and January 2019, 300 women were randomized equally to sildenafil citrate or placebo. Sildenafil citrate reduced the risk of emergency operative birth by 51% (18% vs 36.7%; relative risk, 0.49, 95% confidence interval, 0.33-0.73, P=.0004, number needed to treat = 5 [3-11]). There was no difference in indices of fetal and uteroplacental perfusion, but these were ascertained in only 71 women. Sildenafil citrate reduced the risk of meconium-stained liquor or pathologic fetal heart rate patterns by 43% (25.3% vs 44.7%; relative risk, 0.57, 95% confidence interval, 0.41-0.79, P=.0005), but its effects on fetal scalp sampling rates (2.0% vs 6.7%; relative risk, 0.30, 95% confidence interval, 0.08-1.07, P=.06) and adverse neonatal outcome (20.7% vs 21.3%; relative risk, 0.97, 95% confidence interval, 0.62-1.50, P=.89) were inconclusive. Only 3.6% of maternal levels of sildenafil citrate or its metabolite were detected in cord blood. No differences in maternal adverse events were seen.

CONCLUSION

Sildenafil citrate reduced operative birth for intrapartum fetal compromise, but much larger phase 3 trials of its effects on mother and child are needed before it can be routinely recommended.

Sildenafil for Antenatal Treatment of Congenital Diaphragmatic Hernia: From Bench to Bedside

BACKGROUND

Persistent pulmonary hypertension (PPH) is one of the main causes of mortality and morbidity in infants affected by congenital diaphragmatic hernia (CDH). Since the structural changes that lead to PPH take place already in utero, a treatment starting in the prenatal phase may prevent the occurrence of this complication.

OBJECTIVE

To summarize the development process of antenatal sildenafil for CDH.

METHODS

The pharmacokinetics and efficacy of sildenafil have been assessed in the rat and the rabbit model. The transfer of the drug through the human placenta has been measured with the ex-vivo placenta perfusion model. Results from this experiment are being incorporated in a pregnancy-physiologically based pharmacokinetic (p- PBPK) model. A phase I-IIb placental transfer and safety study is ongoing.

RESULTS

Sildenafil administration to pregnant rats and rabbits led to therapeutic foetal drug levels without maternal and foetal toxicity, although it was associated with impaired vascular development in foetuses with nonhypoplastic lungs. Peak concentrations and 24-hour exposure were higher in pregnant rabbits compared to nonpregnant ones. In rat and rabbit foetuses with CDH, sildenafil rescued the lung vascular anomalies and partially improved parenchymal development. Sildenafil crossed the human placenta at a high rate ex-vivo, independently from the initial maternal concentration.

CONCLUSION

There is preclinical evidence that maternally administered sildenafil prevents the vascular changes that lead to PPH in CDH newborns. The phase I/IIb clinical study together with the p-PBPK model will define the maternal dose needed for a therapeutic effect in the foetus. Foetal safety will be investigated both in the clinical study and in the sheep. The final step will be a multicentre, randomized, placebo-controlled trial.

Differential expression of the inflammasome complex genes in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder involving heterogeneous clinical manifestations and numerous susceptibility genes. Several findings evidence the critical role of inflammasomes in the predisposition to autoimmune diseases and in SLE. We investigated whether inflammasome polymorphins could affect susceptibility to develop and/or severity SLE. Moreover, differences in inflammasome activation in peripheral blood were also evaluated in SLE patients and controls. The distribution of 13 SNPs in eight inflammasome genes was evaluated. To assess inflammasome priming in peripheral blood monocytes of SLE and controls, differential expression of selected inflammasome genes and IL-1ß production was analyzed in resting condition as well as after LPS and ATP stimulation. Results showed that the gain-of-function variant rs10754558 (NLRP3) was significantly more frequent in SLE patients with nephritis, reinforcing the concept of a key role of NLRP3 inflammasome not only in SLE but also especially in kidney disease. SLE monocytes in resting condition showed a higher level of IL-1ß expression and produced higher levels of IL-1ß when stimulated with LPS+ATP comparing to controls. The stimulation induced a significant expression of NLRP1, AIM2, CASP1, and IL1B genes, suggesting that the NLRP1 inflammasome is responsible for the IL-1ß production observed in monocytes. These data emphasized once more the important contribution of inflammasome in SLE-associated inflammation.

Does Pentaerytrithyltetranitrate reduce fetal growth restriction in pregnancies complicated by uterine mal-perfusion? Study protocol of the PETN-study: a randomized controlled multicenter-trial

BACKGROUND

Affecting approximately 10% of pregnancies, fetal growth restriction (FGR), is the most important cause of perinatal mortality and morbidity. Impaired placental function and consequent mal-perfusion of the placenta is the leading cause of FGR. Although, screening for placental insufficiency based on uterine artery Doppler measurement is well established, there is no treatment option for pregnancies threatened by FGR. The organic nitrate pentaerithrityl tetranitrate (PETN) is widely used for the treatment of cardiovascular disease and has been shown to have protective effects on human endothelial cells. In a randomized placebo controlled pilot-study our group could demonstrate a risk reduction of 39% for the development of FGR, and FGR or death, by administering PETN to patients with impaired uterine artery Doppler at mid gestation. To confirm these results a prospective randomized placebo controlled double-blinded multicentre trial was now initiated.

METHOD

The trial has been initiated in 14 centres in Germany. Inclusion criteria are abnormal uterine artery Doppler, defined by mean PI > 1.6, at 190 to 226 weeks of gestation in singleton pregnancies. Included patients will be monitored in 4-week intervals. Primary outcome measures are development of FGR (birth weight < 10th percentile), severe FGR (birth weight < 3rd centile) and perinatal death. Placental abruption, birth weight below the 3rd, 5th and 10th centile, development of FGR requiring delivery before 34 weeks` gestation, neonatal intensive care unit admission, and spontaneous preterm delivery < 34 weeks` and 37 weeks` gestation will be assessed as secondary endpoints. Patient enrolment was started in August 2017. Results are expected in 2020.

DISCUSSION

During the past decade therapeutic agents with possible perfusion optimizing potential have been evaluated in clinical trials to treat FGR. Meta-analysis and sub-analysis of trials targeting preeclampsia revealed ASS to have a potential in reducing FGR. Phosphodiesterase-type-5 inhibitors have recently been tested in a worldwide RCT for therapy of established FGR, failing to show an effect on neonatal outcome. The ongoing multicenter trial will, by confirming our previous results, finally provide a therapeutic option in cases at risk for FGR.

TRIAL REGISTRATION

DRKS00011374 registered at September 29th, 2017 and NCT03669185 , registered September 13th, 2018.

Sildenafil crosses the placenta at therapeutic levels in a dually perfused human cotyledon model

BACKGROUND

Sildenafil already is administered during gestation in patients with pulmonary hypertension and is under evaluation as a treatment for several pregnancy complications, such as preeclampsia and intrauterine growth restriction. Animal studies have shown a potential therapeutic effect of the drug in fetuses with congenital diaphragmatic hernia, rescuing peripheral pulmonary vasculature, and airway phenotype. When considering this drug for evaluation in a clinical trial, data on effective human placental drug passage are required.

OBJECTIVE

We quantified transplacental passage of sildenafil in the ex vivo dually perfused cotyledon model.

STUDY DESIGN

Six placentas that were collected after term delivery from healthy volunteers were cannulated and perfused dually. Sildenafil citrate was added to the maternal circulation at 2 different concentrations: 500 ng/mL, which represented the maximum tolerated concentration (n=3), and 50 ng/mL, which represented the therapeutic concentration (n=3). Samples were collected from both the fetal and the maternal reservoir at 0, 6, 30, 60, 90, 120, 150, and 180 minutes; the concentrations of sildenafil and its metabolite desmethyl-sildenafil were determined with the use of high performance liquid chromatography. The fetal/maternal concentration ratio was calculated for each timepoint. Transfer clearance was calculated as the rate of maternal to fetal passage/maternal concentration.

RESULTS

Sildenafil crossed the placenta at both maximal and therapeutic concentrations. Maternal and fetal levels reached a plateau at 90-120 minutes. Transfer clearance was the highest during the first hour of perfusion: 3.15 mL/min (range, 2.14-3.19 mL/min) for the maximum tolerated concentration and 3.07mL/min (range, 2.75-3.42 mL/min) for the therapeutic concentration (not significant). The fetomaternal concentration ratio significantly increased over time, up to 0.91±0.16 for the maximal concentration and 0.95±0.22 for the therapeutic concentration at the end of the perfusion (not significant). Desmethyl-sildenafil was not detected in any sample.

CONCLUSION

Sildenafil crosses the term placenta at a relatively high rate ex vivo, which suggests that there is sufficient placental transfer to reach clinically active fetal drug levels at the currently used maternal doses.

Anesthetic Treatment of Cardiac Disease During Pregnancy

PURPOSE OF REVIEW

This review summarizes the pathophysiology, peripartum treatment, and anesthetic management of parturients with cardiac disease. Valvular disease, coronary disease, and cardiomyopathy are specifically addressed in the context of the normal physiologic changes of pregnancy. We offer recommendations for anesthetic approaches, hemodynamic goals with an emphasis on interdisciplinary planning between anesthesiologists, cardiologists, cardiothoracic surgeons, obstetricians, maternal fetal medicine specialists, and neonatologists.

RECENT FINDINGS

Vaginal delivery with neuraxial analgesia can be well tolerated by many pregnant patients with cardiac disease when coordinated by an interdisciplinary team of experts. Cardiac disease in pregnancy can present a significant challenge for the interdisciplinary care team. A detailed understanding of each patient's cardiac pathology and the physiologic changes of pregnancy are critical to ensure a safe and successful labor and delivery. Optimized medical therapy in the peripartum period and neuraxial anesthesia with the judicious use of vasoactive agents can be of great benefit for these parturients. As is generally the case, cesarean delivery should be primarily reserved for obstetric indications and maternal wellbeing, with careful consideration of the fetus to guide best practices.

Acute tocolysis for uterine tachysystole or suspected fetal distress

BACKGROUND

Uterine tachysystole (more than 5 contractions per 10 minutes in 2 consecutive intervals) is common during labour, particularly with use of labour-stimulating agents. Tachysystole may reduce fetal oxygenation by interrupting maternal blood flow to the placenta during contractions. Reducing uterine contractions may improve placental blood flow, improving fetal oxygenation. This review aimed to evaluate the use of tocolytics to reduce or stop uterine contractions for improvement of the condition of the fetus in utero. This new review supersedes an earlier Cochrane Review on the same topic.

OBJECTIVES

To assess the effects of the use of acute tocolysis during labour for uterine tachysystole or suspected fetal distress, or both, on fetal, maternal and neonatal outcomes.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (2 February 2018), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) evaluating acute tocolysis for uterine tachysystole, intrapartum fetal distress, or both.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane.

MAIN RESULTS

We included eight studies (734 women), conducted in hospital settings, predominantly in high-income countries (USA, Austria, Uruguay). Two trials were conducted in upper and lower middle-income countries (South Africa, Sri Lanka). The hospital facilities all had the capacity to perform caesarean section. Overall, the studies had a low risk of bias, except for methods to maintain blinding. All of the trials used a selective beta₂ (ß₂)-adrenergic agonist in one arm, however the drug used varied, as did the comparator. Limited information was available on maternal outcomes.Selective ß₂-adrenergic agonist versus no tocolytic agent, whilst awaiting emergency deliveryThere were two stillbirths, both in the no tocolytic control group (risk ratio (RR) 0.23, 95% confidence interval (CI) 0.01 to 4.55; 2 studies, 57 women; low-quality evidence). One had gross hydrocephalus and the second occurred with vaginal delivery after waiting 55 minutes for caesarean section. The decision for caesarean section delivery was an inclusion criterion in both studies so we could not assess this as an outcome under this comparison. Abnormal fetal heart trace is probably lower with tocolytic treatment (RR 0.28, 95% CI 0.08 to 0.95; 2 studies, 43 women; moderate-quality evidence). The effects on the number of babies with Apgar score below seven were uncertain (low-quality evidence).Intravenous (IV) atosiban versus IV hexoprenaline (1 study, 26 women) One infant in the hexoprenaline group required > 24 hours in the neonatal intensive care unit (NICU) following a forceps delivery (RR 0.33, 95% CI 0.01 to 7.50; low-quality evidence). There were no fetal or neonatal mortalities and no Apgar scores below seven. There was one caesarean delivery in the IV hexoprenaline group (RR 0.33, 95% CI 0.01 to 7.50; low-quality evidence), and one case of abnormal fetal heart score in the atosiban group (RR 3.00, 95% CI 0.13 to 67.51; very low-quality evidence).IV fenoterol bromhydrate versus emergency delivery (1 study, 390 women) No data were reported for perinatal death, severe morbidity or fetal or neonatal mortality. IV fenoterol probably increases the risk of caesarean delivery (RR 1.12, 95% CI 1.04 to 1.22; moderate-quality evidence). Fenoterol may have little or no effect on the risk of Apgar scores below seven (RR 1.28, 95% CI 0.35 to 4.68; low-quality evidence).IV hexoprenaline versus no tocolytic agent, whilst awaiting emergency delivery (1 study, 37 women) No data were reported for perinatal death or severe morbidity. There were two fetal deaths in the no tocolytic control group (RR 0.23, 95% CI 0.01 to 4.55; low-quality evidence). The rate of caesarean delivery was not reported. There were two babies with Apgar scores below seven in the control group and none in the hexoprenaline group (RR 0.24, 95% CI 0.01 to 4.57; 35 women; low-quality evidence).Subcutaneous terbutaline versus IV magnesium sulphate (1 study, 46 women)No data were reported for perinatal death, severe morbidity or fetal or neonatal mortality. The decision for caesarean section was an inclusion criterion, so we could not assess this. The effects on abnormal fetal heart trace are uncertain (very low-quality evidence).Subcutaneous terbutaline with continuation of oxytocic infusion versus cessation of oxytocic infusion without tocolytic agent (1 study, 28 women) No data were reported for perinatal death, severe morbidity or fetal or neonatal mortality. There may be little or no difference in the rates of caesarean delivery in the subcutaneous terbutaline (8/15) and control groups (4/13) (RR 1.73, 95% CI 0.68 to 4.45; low-quality evidence). There were no cases of Apgar scores below seven or abnormal fetal heart trace.Subcutaneous terbutaline versus no tocolytic agent, whilst awaiting emergency delivery (1 study, 20 women) No data were reported for perinatal death or severe morbidity. There were no fetal or neonatal mortalities. The decision for caesarean section was an inclusion criterion, so we could not assess this. There were two babies with Apgar scores below seven in the control group and none in the terbutaline group (RR 0.17, 95% CI 0.01 to 3.08; low-quality evidence).IV terbutaline versus IV nitroglycerin (1 study, 110 women)No data were reported for perinatal death or severe morbidity or fetal or neonatal mortality. There may be little or no difference in the rates of caesarean delivery between the IV terbutaline (30/57) and control groups (29/53) (RR 0.96, 95% CI 0.68 to 1.36; low-quality evidence). There were no cases of Apgar scores below seven.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the effects of tocolytics for uterine tachysystole or suspected fetal distress during labour. The clinical significance for some of the improvements in measures of fetal well-being with tocolytics is unclear. The sample sizes were too small to detect effects on neonatal morbidity, mortality or serious adverse effects. The majority of studies are from high-income countries in facilities with access to caesarean section, which may limit the generalisability of the results to lower-resource settings, or settings where caesarean section is not available.Further well-designed and adequately powered RCTs are required to evaluate clinically relevant indicators of maternal and neonatal morbidity and mortality.

Pregnancy affects the pharmacokinetics of sildenafil and its metabolite in the rabbit

1. There is growing interest in the use of sildenafil during pregnancy for various maternal and fetal conditions. This study aims to investigate the effect of pregnancy on the maternal pharmacokinetics (PK) of sildenafil and its main metabolite desmethylsildenafil in rabbits. Using NONMEM, population PK modeling was performed based on plasma samples from 31 rabbits of whom 15 were pregnant and 16 were not. All received a single subcutaneous sildenafil dose of 10 mg/kg. One sample was obtained per rabbit at either 30, 60, 120, 360, 720 or 1320 min after sildenafil administration. 2. A two- and one-compartment PK-model best described the data for sildenafil and desmethylsildenafil, respectively. Compared to non-pregnant rabbits, the central and peripheral volume of distribution and inter-compartmental clearance of sildenafil were lower in pregnant rabbits [32.1 versus 12.2 L, 110 versus 44.4 L and 25.5 versus 12.1 L/h; all p < 0.05]. The formation clearance from sildenafil to desmethylsildenafil was also reduced during pregnancy [13.3 versus 7.8 L/h; p < 0.05]. 3. In contrast, the elimination clearance of desmethylsildenafil, was higher in pregnancy [73.5 versus 116. 9; p < 0.05]. In rabbits, pregnancy impacts PK parameters of sildenafil and its metabolite, leading to an increased peak concentration and 24 h exposure for sildenafil and a decreased 24 h exposure for desmethylsildenafil.

Current and future antenatal management of isolated congenital diaphragmatic hernia

Congenital diaphragmatic hernia is surgically correctable, yet the poor lung development determines mortality and morbidity. In isolated cases the outcome may be predicted prenatally by medical imaging. Cases with a poor prognosis could be treated before birth. However, prenatal modulation of lung development remains experimental. Fetoscopic endoluminal tracheal occlusion triggers lung growth and is currently being evaluated in a global clinical trial. Prenatal transplacental sildenafil administration may in due course be a therapeutic approach, reducing the occurrence of persistent pulmonary hypertension, either alone or in combination with fetal surgery.