Physiopathologie de la pré-éclampsie

Preeclampsia and Venous Thromboembolism: Pathophysiology and Potential Therapy

Preeclampsia (PET) is a multisystem inflammatory disorder that represents a leading cause of feto-maternal morbidity and mortality, complicating 2-5% of all pregnancies. PET incurs an increased risk of venous thromboembolism, which is one of the leading causes of death in pregnancy and in the postpartum period. This prothrombotic phenotype is attributable to the maternal phase of PET, which is characterized by a systemic inflammatory response and coagulation activation. Research continues to be undertaken in terms of preventative measures, however, currently revolves around pharmacological low dose aspirin initiated in the first trimester of pregnancy for those with risk factors. Treatment involves antenatal corticosteroids for fetal lung development in preterm birth, parenteral magnesium sulfate for fetal neuroprotection and maternal seizure prophylaxis, and timely birth of the fetus and placenta being the only definitive treatment of PET. Patients with a venous thromboembolism (VTE) risk deemed to be >1-3% are treated with pharmacological thromboprophylaxis in the form of low molecular weight heparin. Completing each woman's VTE risk assessment is crucial, particularly in the setting of PET, as there is also a proven associated competing hemorrhagic risk.

Role of oxidative stress in the dysfunction of the placental endothelial nitric oxide synthase in preeclampsia

Preeclampsia (PE) is a multifactorial pregnancy disease, characterized by new-onset gestational hypertension with (or without) proteinuria or end-organ failure, exclusively observed in humans. It is a leading cause of maternal morbidity affecting 3–7% of pregnant women worldwide. PE pathophysiology could result from abnormal placentation due to a defective trophoblastic invasion and an impaired remodeling of uterine spiral arteries, leading to a poor adaptation of utero-placental circulation. This would be associated with hypoxia/reoxygenation phenomena, oxygen gradient fluctuations, altered antioxidant capacity, oxidative stress, and reduced nitric oxide (NO) bioavailability. This results in part from the reaction of NO with the radical anion superoxide (O₂^•−), which produces peroxynitrite ONOO^-, a powerful pro-oxidant and inflammatory agent. Another mechanism is the progressive inhibition of the placental endothelial nitric oxide synthase (eNOS) by oxidative stress, which results in eNOS uncoupling via several events such as a depletion of the eNOS substrate L-arginine due to increased arginase activity, an oxidation of the eNOS cofactor tetrahydrobiopterin (BH4), or eNOS post-translational modifications (for instance by S-glutathionylation). The uncoupling of eNOS triggers a switch of its activity from a NO-producing enzyme to a NADPH oxidase-like system generating O₂^•−, thereby potentiating ROS production and oxidative stress. Moreover, in PE placentas, eNOS could be post-translationally modified by lipid peroxidation-derived aldehydes such as 4-oxononenal (ONE) a highly bioreactive agent, able to inhibit eNOS activity and NO production. This review summarizes the dysfunction of placental eNOS evoked by oxidative stress and lipid peroxidation products, and the potential consequences on PE pathogenesis.

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Physiological ROS production is enhanced during pregnancy.

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eNOS is one of the main target of oxidative stress in PE placenta.

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eNOS is S-glutathionylated in PE placentas.

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eNOS is modified by lipid oxidation products in PE placentas.

The cause of birth is associated with neonatal prognosis in late preterm singletons

INTRODUCTION

Recent studies have shown that the cause of very preterm births may be related to neonatal morbidity and mortality. Even though these risks are lower among late preterm births, this group accounts for the vast majority of all preterm births. The objective of this study was to evaluate the relation of neonatal morbidity and mortality to the cause of late preterm birth.

MATERIALS AND METHODS

This retrospective observational cohort study included all women who gave birth to liveborn singletons from 34 to 36 weeks+6 days of gestation in a French level III maternity hospital in the 5-year period 2013-2017. The causes of preterm delivery were divided into 6 mutually exclusive groups. The main outcome was a composite neonatal morbidity criterion, defined by at least one among the following criteria: neonatal respiratory distress, neurological complications, neonatal sepsis, severe necrotizing enterocolitis, and neonatal hypoglycemia. We analyzed the association between cause of preterm delivery and neonatal morbidity after adjustment for gestational age and antenatal corticosteroid therapy. The reference group was preterm labor, defined by spontaneous preterm labor with intact membranes.

RESULTS

During the study period, there were a total of 27 110 births, including 1114 singleton births at 34 to 36 weeks of gestation + 6 days (4.1%). Among the 968 late preterm births included, the risk of neonatal morbidity in the group with preterm premature rupture of membranes (PPROM) was similar to that in the preterm labor (reference) group: adjusted odds ratio (aOR) 1.2 (95% CI, 0.8-1.8). All the other causes of late preterm birth were associated with a higher risk of neonatal morbidity than the reference group: aOR 2.0 [95% CI, 1.1-3.5] for hypertensive disorders without suspected fetal growth restriction (FGR) (9.1% of cases), aOR 2.4 [95% CI, 1.4-4.2] for hypertensive disorders with suspected FGR (8.9%), aOR 4.2 [95% CI, 2.2-8.0] for suspected FGR without hypertensive disorders (5.8%), and aOR 4.4 [95% CI, 2.2-8.8] for vaginal bleeding related to abnormal placental insertion (4.7%).

CONCLUSION

Among infants born from 34 to 36 weeks + 6 days of gestation, PPROM and preterm labor had similar risks of neonatal morbidity, while the other causes were associated with a risk of neonatal morbidity at least twice that with preterm labor.

Aspirin for prevention of preeclampsia and fetal growth restriction

For the past decades, growing attention has been given to aspirin use during pregnancy. It favors placentation by its proangiogenic, antithrombotic, and anti-inflammatory effects. Therefore, low doses of aspirin are prescribed in the prevention of placenta-mediated complications, mainly preeclampsia and fetal growth restriction. However, questions regarding its clinical application are still debated. Aspirin is effective in preventing preeclampsia in a high-risk population. Most guidelines recommend that risk stratification should rely on medical history. Nevertheless, screening performances dramatically improve if biochemical and biophysical markers are included. Concerning the appropriate timing and dose, latest studies suggest aspirin should be started before 16 weeks of pregnancy and at a daily dose of 100 mg or more. Further studies are needed to improve the identification of patients likely to benefit from prophylactic aspirin. Besides, the role of aspirin in the prevention of fetal growth restriction is still questioned.

[Cell-free DNA fraction: Can it be used to evaluate the risk of obstetrical issues?]

OBJECTIVE

The aim of the study was to evaluate if fetal cell-free DNA (cfDNA) fraction circulating in maternal blood at the beginning of the second trimester is associated with obstetrical complications.

METHODS

This is a retrospective unicentric study conducted at the hospital of Poissy Saint Germain between the 1^st January 2015, and the 31^st. December 2016, Each woman who had a genetic counseling in order to realize a non-invasive prenatal test (NIPT) was included. Only singleton pregnancies with a documented-issue were analysed. The primary criteria was a composite criteria, defined as the occurrence of preeclampsia, in utero fetal growth, or a spontaneous preterm delivery. A descriptive analyse was first conducted, secondly completed by a sub-group one: "high fetal fraction" (>90^th percentile) group, "low fetal-fraction" group (<10^th percentile) and "medium fetal-fraction" (control group) group.

RESULTS

A total of 417 women had a cfDNA test, which was performed at a mean gestational age of 17.1 weeks of gestation. A total of 17% of pregnancies met the primary criteria. Among them, there were 8 (1.9%) pre-eclampsia, 49 (11.8%) intra-uterine growth restriction and 14 (3.4%) preterm births. There was no significant difference for the occurrence of the primary criteria (P>0.99) and of each obstetrical complication between each group.

CONCLUSION

Fetal cf-DNA fraction measured at the beginning of the second trimester is not associated with common obstetrical complications.

Selective feticide as a treatment of severe preeclampsia in discordant twins

Multifetal gestation is often complicated by the development of preeclampsia. In some twin gestations, preeclampsia develops in association with restricted fetal growth of only one fetus. Instead of termination of the entire pregnancy, we investigated an alternative approach to the management of such pregnancies that might allow unharmed survival of the normal twin. We present a case of preeclampsia in twin discordance with severe fetal growth restriction at 25 weeks of gestation. Preeclampsia was linked to a lethal condition in one twin and was treated with selective feticide in an effort to reverse preeclampsia. Inasmuch as the fetal prognosis was extremely poor for the abnormal fetus, selective feticide was a reasonable therapeutic option. Maternal symptoms resolved, allowing continuation of the pregnancy for 4 weeks before delivery of the healthy fetus. We maintain that selective termination induced a decrease in the release of substances involved in the physiopathology of preeclampsia, which allowed the continuation of the pregnancy with close follow-up. This report highlights the link between placental pathology and the disease process of preeclampsia and further supports selective termination as a reasonable management strategy in carefully selected cases of discordant twins.

[Targeted screening for pre-eclampsia in the first trimester of pregnancy at Toulouse University Hospital]

GOALS

Preeclampsia (PE) is a leading cause of maternal and neonatal morbidity and mortality. Early treatment by aspirin has been shown to significantly reduce PE risk before 37weeks supporting the implementation of first-trimester screening.

SUBJECTS AND METHODS

A targeted screening was recently implemented at Toulouse University Hospital for women in their first pregnancy or those with personal or familial history of PE. It uses Fetal Medicine Foundation (FMF) algorithm that combines maternal characteristics, clinical, biophysical and biochemical (PAPP-A, Pregnancy Associated Plasma Protein-A, and PlGF, Placental Growth Factor) data. We describe this first population of pregnant women and compare our results with those of a mini-test that excludes PlGF and biophysical data.

RESULTS

Between October 2016 and September 2017, 500women have benefited from this screening. In such targeted population, we identified 3,6 % (n=18) of women at high risk to develop PE before 34weeks and 9,6 % (n=48) of women at high risk to develop PE between 34 and 37weeks. When we recalculated the risk using the mini-test, only 10women (56 %) were identified at high risk of early PE.

CONCLUSION

For the first time in France, we report the result of a targeted screening of PE during the first trimester using the FMF algorithm. We describe the screened population and show that it is more efficient than the mini-test.