Neonatal platelet reactivity and serum thromboxane B2 production in whole blood: the effect of maternal low dose aspirin

Primary hemostasis in fetal growth restricted neonates studied via PFA-100 in cord blood samples

BACKGROUND

Platelet function of fetal growth restricted (FGR) neonates remains a field of debate. Platelet function analyzer (PFA-100) offers a quantitative in vitro assessment of primary, platelet-related hemostasis. Our aim was to examine platelet function using PFA-100 in FGR neonates and associate our results with perinatal parameters.

METHODS

PFA-100 was applied on 74 FGR neonates, 48 full-term (>37 weeks' gestation) and 26 preterm neonates (<37 weeks). The control group consisted of 118 healthy neonates. Two closure times (CTs) with COL/EPI and COL/ADP cartridges were determined on cord blood samples for each subject. Statistical analysis was performed by SAS 9.4. The statistical significance level was set at 0.05 and all tests were two-tailed.

RESULTS

COL/EPI CTs were prolonged in FGR (median 132 s, IQR 95-181 s) compared with control neonates (median 112.5 s, IQR 93-145 s), p = 0.04. Median COL/EPI CT for term and preterm FGR neonates was 126 s (IQR 90-157 s) and 137 s (IQR 104-203), respectively (p = 0.001), and COL/ADP CT was 70 s (IQR 62-80 s) for term and 75 s (IQR 68-82 s) for preterm FGR neonates (p = 0.08). Among FGR neonates, COL/EPI CT was related with delivery time (with preterm neonates exhibiting prolonged COL/EPI CTs), p = 0.05. No correlation was proved between both CTs and hematological parameters in FGR neonates.

CONCLUSION

FGR neonates showed impaired platelet function via PFA-100, with preterm FGR neonates confronting the greatest risk. Prolonged COL/EPI CTs in FGR neonates seemed to be independent of hematological parameters and could warn for closer evaluation during the first days of their lives.

Antiplatelet agents for preventing pre-eclampsia and its complications

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, low-dose aspirin in particular, might prevent or delay development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents, such as aspirin and dipyridamole, when given to women at risk of developing pre-eclampsia.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (30 March 2018), and reference lists of retrieved studies. We updated the search in September 2019 and added the results to the awaiting classification section of the review.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent were included. Studies only published in abstract format were eligible for inclusion if sufficient information was available. We would have included cluster-randomised trials in the analyses along with individually-randomised trials, if any had been identified in our search strategy. Quasi-random studies were excluded. Participants were pregnant women at risk of developing pre-eclampsia. Interventions were administration of an antiplatelet agent (such as low-dose aspirin or dipyridamole), comparisons were either placebo or no antiplatelet.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trials for inclusion and extracted data independently. For binary outcomes, we calculated risk ratio (RR) and its 95% confidence interval (CI), on an intention-to-treat basis. For this update we incorporated individual participant data (IPD) from trials with this available, alongside aggregate data (AD) from trials where it was not, in order to enable reliable subgroup analyses and inclusion of two key new outcomes. We assessed risk of bias for included studies and created a 'Summary of findings' table using GRADE.

MAIN RESULTS

Seventy-seven trials (40,249 women, and their babies) were included, although three trials (relating to 233 women) did not contribute data to the meta-analysis. Nine of the trials contributing data were large (> 1000 women recruited), accounting for 80% of women recruited. Although the trials took place in a wide range of countries, all of the nine large trials involved only women in high-income and/or upper middle-income countries. IPD were available for 36 trials (34,514 women), including all but one of the large trials. Low-dose aspirin alone was the intervention in all the large trials, and most trials overall. Dose in the large trials was 50 mg (1 trial, 1106 women), 60 mg (5 trials, 22,322 women), 75mg (1 trial, 3697 women) 100 mg (1 trial, 3294 women) and 150 mg (1 trial, 1776 women). Most studies were either low risk of bias or unclear risk of bias; and the large trials were all low risk of bas. Antiplatelet agents versus placebo/no treatment The use of antiplatelet agents reduced the risk of proteinuric pre-eclampsia by 18% (36,716 women, 60 trials, RR 0.82, 95% CI 0.77 to 0.88; high-quality evidence), number needed to treat for one women to benefit (NNTB) 61 (95% CI 45 to 92). There was a small (9%) reduction in the RR for preterm birth <37 weeks (35,212 women, 47 trials; RR 0.91, 95% CI 0.87 to 0.95, high-quality evidence), NNTB 61 (95% CI 42 to 114), and a 14% reduction infetal deaths, neonatal deaths or death before hospital discharge (35,391 babies, 52 trials; RR 0.85, 95% CI 0.76 to 0.95; high-quality evidence), NNTB 197 (95% CI 115 to 681). Antiplatelet agents slightly reduced the risk of small-for-gestational age babies (35,761 babies, 50 trials; RR 0.84, 95% CI 0.76 to 0.92; high-quality evidence), NNTB 146 (95% CI 90 to 386), and pregnancies with serious adverse outcome (a composite outcome including maternal death, baby death, pre-eclampsia, small-for-gestational age, and preterm birth) (RR 0.90, 95% CI 0.85 to 0.96; 17,382 women; 13 trials, high-quality evidence), NNTB 54 (95% CI 34 to 132). Antiplatelet agents probably slightly increase postpartum haemorrhage > 500 mL (23,769 women, 19 trials; RR 1.06, 95% CI 1.00 to 1.12; moderate-quality evidence due to clinical heterogeneity), and they probably marginally increase the risk of placental abruption, although for this outcome the evidence was downgraded due to a wide confidence interval including the possibility of no effect (30,775 women; 29 trials; RR 1.21, 95% CI 0.95 to 1.54; moderate-quality evidence). Data from two large trials which assessed children at aged 18 months (including results from over 5000 children), did not identify clear differences in development between the two groups.

AUTHORS' CONCLUSIONS

Administering low-dose aspirin to pregnant women led to small-to-moderate benefits, including reductions in pre-eclampsia (16 fewer per 1000 women treated), preterm birth (16 fewer per 1000 treated), the baby being born small-for-gestational age (seven fewer per 1000 treated) and fetal or neonatal death (five fewer per 1000 treated). Overall, administering antiplatelet agents to 1000 women led to 20 fewer pregnancies with serious adverse outcomes. The quality of evidence for all these outcomes was high. Aspirin probably slightly increased the risk of postpartum haemorrhage of more than 500 mL, however, the quality of evidence for this outcome was downgraded to moderate, due to concerns of clinical heterogeneity in measurements of blood loss. Antiplatelet agents probably marginally increase placental abruption, but the quality of the evidence was downgraded to moderate due to low event numbers and thus wide 95% CI. Overall, antiplatelet agents improved outcomes, and at these doses appear to be safe. Identifying women who are most likely to respond to low-dose aspirin would improve targeting of treatment. As almost all the women in this review were recruited to the trials after 12 weeks' gestation, it is unclear whether starting treatment before 12 weeks' would have additional benefits without any increase in adverse effects. While there was some indication that higher doses of aspirin would be more effective, further studies would be warranted to examine this.

Role for the thromboxane A2 receptor β-isoform in the pathogenesis of intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a pathology of pregnancy that results in failure of the fetus to reach its genetically determined growth potential. In developed nations the most common cause of IUGR is impaired placentation resulting from poor trophoblast function, which reduces blood flow to the fetoplacental unit, promotes hypoxia and enhances production of bioactive lipids (TXA₂ and isoprostanes) which act through the thromboxane receptor (TP). TP activation has been implicated as a pathogenic factor in pregnancy complications, including IUGR; however, the role of TP isoforms during pregnancy is poorly defined. We have determined that expression of the human-specific isoform of TP (TPβ) is increased in placentae from IUGR pregnancies, compared to healthy pregnancies. Overexpression of TPα enhanced trophoblast proliferation and syncytialisation. Conversely, TPβ attenuated these functions and inhibited migration. Expression of the TPβ transgene in mice resulted in growth restricted pups and placentae with poor syncytialisation and diminished growth characteristics. Together our data indicate that expression of TPα mediates normal placentation; however, TPβ impairs placentation, and promotes the development of IUGR, and represents an underappreciated pathogenic factor in humans.

Neonatal Platelet Function

Similarly to the development of the plasma coagulation system, which matures during the early weeks and months of life, age-dependent mechanisms and developmental changes influence platelet production and function in neonates. Platelet function testing on cord blood and peripheral blood demonstrates a generalized platelet hyporeactivity, during the first days of life. This reactivity reaches normal adult levels between the fifth and ninth day of life. The persistence of hyporeactivity after the tenth day of life might indeed suggest a platelet disorder.

Pharmacodynamic effects of clopidogrel in pediatric cardiac patients: a comparative study of platelet aggregation response

Little data on pediatric percent platelet aggregation (%PA) exist in the literature, particularly in cardiac patients and in response to clopidogrel. The objectives were to estimate the %PA range expected in pediatric patients and to measure the clopidogrel effect on %PA in the PICOLO (Platelet Inhibition in Children on Clopidogrel) trial. To estimate a neonatal/infant %PA response range, %PA induced by 5 µM adenosine diphosphate (ADP) was assessed using light transmission aggregometry in 16 cord and 11 normal adult blood samples and prior to clopidogrel therapy in 49 neonatal and 49 infant/toddler cardiac patients enrolled in PICOLO. The %PA induced by 5 µM thrombin receptor-activating peptide (TRAP) was also assessed for 10 neonates and 21 infants/toddlers enrolled in PICOLO and compared with 11 adult samples. Percent inhibition of platelet aggregation (%IPA) induced by 5 µM ADP at steady-state clopidogrel levels was assessed in 33 neonates and 39 infants/toddlers. ADP-induced %PA was lowest in cord blood samples, intermediate in study neonates and infants/toddlers, and highest in adults. Similarly, TRAP-induced platelet aggregation was lower in neonates and infants/toddlers than adults. For all groups, %PA and %IPA were highly variable, with 11% of neonates and 13% of infants/toddlers showing <10% IPA. In conclusion, ADP- and TRAP-induced %PA is lower in pediatric cardiac patients than normal adults, but highly variable in both. The lower baseline %PA may explain why the pediatric clopidogrel dose providing 30-50% IPA (0.20 mg/kg/day) is lower than a simple weight-based extrapolation of the adult dose (75 mg/day) providing similar inhibition.

VTE, thrombophilia, antithrombotic therapy, and pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

The use of anticoagulant therapy during pregnancy is challenging because of the potential for both fetal and maternal complications. This guideline focuses on the management of VTE and thrombophilia as well as the use of antithrombotic agents during pregnancy.

METHODS

The methods of this guideline follow the Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

We recommend low-molecular-weight heparin for the prevention and treatment of VTE in pregnant women instead of unfractionated heparin (Grade 1B). For pregnant women with acute VTE, we suggest that anticoagulants be continued for at least 6 weeks postpartum (for a minimum duration of therapy of 3 months) compared with shorter durations of treatment (Grade 2C). For women who fulfill the laboratory criteria for antiphospholipid antibody (APLA) syndrome and meet the clinical APLA criteria based on a history of three or more pregnancy losses, we recommend antepartum administration of prophylactic or intermediate-dose unfractionated heparin or prophylactic low-molecular-weight heparin combined with low-dose aspirin (75-100 mg/d) over no treatment (Grade 1B). For women with inherited thrombophilia and a history of pregnancy complications, we suggest not to use antithrombotic prophylaxis (Grade 2C). For women with two or more miscarriages but without APLA or thrombophilia, we recommend against antithrombotic prophylaxis (Grade 1B).

CONCLUSIONS

Most recommendations in this guideline are based on observational studies and extrapolation from other populations. There is an urgent need for appropriately designed studies in this population.

Aspirin resistance

The development of adverse cardiovascular events despite aspirin use has established an interest in a possible resistance to the drug. Several definitions have been set and various laboratory testing modalities are available. This has led to a wide range of prevalence reports in different clinical entities. The etiologic mechanism has been related to clinical, genetic, and other miscellaneous factors. The clinical implications of this phenomenon are significant and warrant concern. Management strategies are currently limited to dosing alteration and introduction of other anitplatelet agents. However, these measures have not met the expected efficacy or safety.

The role of aspirin in cardiovascular prevention: implications of aspirin resistance

Aspirin is well recognized as an effective antiplatelet drug for secondary prevention in subjects at high risk of cardiovascular events. However, most patients receiving long-term aspirin therapy still remain at substantial risk of thrombotic events due to insufficient inhibition of platelets, specifically via the thromboxane A2 pathway. Although the exact prevalence is unknown, estimates suggest that between 5.5% and 60% of patients using this drug may exhibit a degree of "aspirin resistance," depending upon the definition used and parameters measured. To date, only a limited number of clinical studies have convincingly investigated the importance of aspirin resistance. Of these, few are of a sufficient scale, well designed, and prospective, with aspirin used at standard doses. Also, most studies do not sufficiently address the issue of noncompliance to aspirin as a frequent, yet easily preventable cause of resistance to this antiplatelet drug. This review article provides a comprehensive overview of aspirin resistance, discussing its definition, prevalence, diagnosis, and therapeutic approaches. Moreover, the clinical implications of aspirin resistance are explored in various cardiovascular disease states, including diabetes mellitus, hypertension, heart failure, and other similar disorders where platelet reactivity is enhanced.

WITHDRAWN: Antiplatelet agents for preventing and treating pre-eclampsia

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a platelet-derived vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, and low dose aspirin in particular, might prevent or delay the development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents when given to women at risk of developing pre-eclampsia, and to those with established pre-eclampsia.

SEARCH STRATEGY

This review drew on the search strategy developed for the Pregnancy and Childbirth Group as a whole. The Cochrane Controlled Trials Register was also searched, The Cochrane Library 1999 Issue 1, Embase was searched from 1994-1999 and hand searches were performed of the congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent during pregnancy. Quasi random study designs were excluded. Participants were pregnant women considered to be at risk of developing pre-eclampsia, and those with pre-eclampsia before delivery. Women treated postpartum were excluded. Interventions were any comparisons of an antiplatelet agent (such as low dose aspirin or dipyridamole) with either placebo or no antiplatelet agent.

DATA COLLECTION AND ANALYSIS

Assessment of trials for inclusion in the review and extraction of data was performed independently and unblinded by two reviewers. Data were entered into the Review Manager software and double checked.

MAIN RESULTS

Forty two trials involving over 32,000 women were included in this review, with 30,563 women in the prevention trials. There is a 15% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents [32 trials with 29,331 women; relative risk (RR) 0.85, 95% confidence interval (0.78, 0.92); Number needed to treat (NNT) 89, (59, 167)]. This reduction is regardless of risk status at trial entry or whether a placebo was used, and irrespective of the dose of aspirin or gestation at randomisation.Twenty three trials (28,268 women) reported preterm delivery. There is a small (8%) reduction in the risk of delivery before 37 completed weeks [RR 0.92, (0.88, 0.97); NNT 72 (44, 200)]. Baby deaths were reported in 30 trials (30,093 women). Overall there is a 14% reduction in baby deaths in the antiplatelet group [RR 0.86, (0.75, 0.98); NNT 250 (125, >10000)]. Small for gestational age babies were reported in 25 trials (20,349 women), with no overall difference between the groups, RR 0.92, (0.84, 1.01). There were no significant differences between treatment and control groups in any other measures of outcome. Five trials compared antiplatelet agents with placebo or no antiplatelet agent for the treatment of pre-eclampsia. There are insufficient data for any firm conclusions about the possible effects of these agents when used for treatment of pre-eclampsia.

AUTHORS' CONCLUSIONS

Antiplatelet agents, in this review largely low dose aspirin, have small-moderate benefits when used for prevention of pre-eclampsia. Further information is required to assess which women are most likely to benefit, when treatment should be started, and at what dose.

Antiplatelet agents for preventing pre-eclampsia and its complications

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, low-dose aspirin in particular, might prevent or delay development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents for women at risk of developing pre-eclampsia.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (July 2006), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2005, Issue 1), EMBASE (1994 to November 2005) and handsearched congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent were included. Quasi-random studies were excluded. Participants were pregnant women at risk of developing pre-eclampsia. Interventions were any comparisons of an antiplatelet agent (such as low-dose aspirin or dipyridamole) with either placebo or no antiplatelet.

DATA COLLECTION AND ANALYSIS

Two authors assessed trials for inclusion and extracted data independently.

MAIN RESULTS

Fifty-nine trials (37,560 women) are included. There is a 17% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents ((46 trials, 32,891 women, relative risk (RR) 0.83, 95% confidence interval (CI) 0.77 to 0.89), number needed to treat (NNT) 72 (52, 119)). Although there is no statistical difference in RR based on maternal risk, there is a significant increase in the absolute risk reduction of pre-eclampsia for high risk (risk difference (RD) -5.2% (-7.5, -2.9), NNT 19 (13, 34)) compared with moderate risk women (RD -0.84 (-1.37, -0.3), NNT 119 (73, 333)). Antiplatelets were associated with an 8% reduction in the relative risk of preterm birth (29 trials, 31,151 women, RR 0.92, 95% CI 0.88 to 0.97); NNT 72 (52, 119)), a 14% reduction in fetal or neonatal deaths (40 trials, 33,098 women, RR 0.86, 95% CI 0.76 to 0.98); NNT 243 (131, 1,666) and a 10% reduction in small-for-gestational age babies (36 trials, 23,638 women, RR 0.90, 95% CI0.83 to 0.98). There were no statistically significant differences between treatment and control groups for any other outcomes.

AUTHORS' CONCLUSIONS

Antiplatelet agents, largely low-dose aspirin, have moderate benefits when used for prevention of pre-eclampsia and its consequences. Further information is required to assess which women are most likely to benefit, when treatment is best started, and at what dose.

Pathophysiology and medical management of systemic hypertension in preeclampsia

Hypertension that complicates preeclampsia in pregnancy is a disorder that requires special consideration in both prevention and pharmacologic treatment. In recent years, few advances have been made regarding the pathophysiology and prevention of preeclampsia; however, there have been some promising results from studies on possible modes of screening women for preeclampsia before clinical signs and symptoms are apparent. The recommendations for first-line drug therapy for the hypertensive complications of preeclampsia have changed little, primarily because first-line medications have had the advantage of extensive research experience. Recent clinical trials have demonstrated the efficacy and safety of various second-line drugs for the hypertensive complications of preeclampsia; whether these therapies can eventually replace the standard recommended first-line medications will require more extensive long-term investigation.

Pathophysiology and Medical Management of Systemic Hypertension in Pregnancy

Hypertension in pregnancy includes a group of distinct disorders that require special consideration in both prevention and pharmacologic treatment. In recent years, there have been few advances regarding the pathophysiology and prevention of preeclampsia or in the recommendations for first-line drug therapy for its hypertensive complications. Similarly, the recommendations for pharmacologic treatment of women with chronic hypertension antedating pregnancy have changed little primarily because first-line medications have the advantage of having had more extensive research experience. Recent clinical trials have demonstrated the efficacy and safety of various second-line drugs for the hypertensive disorders of pregnancy; whether these therapies can eventually replace the standard recommended medications will require more extensive long-term investigation.

Antirheumatic Drugs in Pregnancy and Lactation

OBJECTIVE

To review the toxicity issues of commonly used antirheumatic drugs in pregnancy and lactation.

METHODS

A review of the medical literature using Medline database via Ovid was performed to identify the toxicities of antirheumatic drugs in pregnancy and lactation.

RESULTS

Many rheumatologic diseases in women often first present during the childbearing years. In most cases, antirheumatic therapy is required for their disease control. Glucocorticoids may be used during pregnancy; however, first-trimester use should be avoided if possible and breastfeeding should occur 4 hours after the last dosing. Nonsteroidal antiinflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX-2) inhibitors should be discontinued 6 to 8 weeks before delivery. NSAIDs are compatible with lactation, although there is potential risk of jaundice and kernicterus. There is insufficient data on COX-2 inhibitors and lactation. Hydroxychloroquine and sulfasalazine may be continued throughout pregnancy and lactation. Methotrexate and leflunomide are contraindicated during pregnancy and lactation. Cyclophosphamide and mycophenolate mofetil should be avoided during pregnancy and lactation. Azathioprine and cyclosporine A could be used with caution during pregnancy if felt there is a need to suppress disease activity. They are not compatible with breastfeeding. There are insufficient data regarding tumor necrosis factor-antagonists, anakinra, and rituximab in relation to pregnancy and lactation. Male patients should be made aware of the effects methotrexate, leflunomide, sulfasalazine, and cyclophosphamide may have on their fertility.

CONCLUSIONS

Health care providers should discuss the risks and benefits of antirheumatic therapy during conception, pregnancy, and lactation with their patients. Better maternal and fetal outcomes can be expected if the pregnancy is planned, the rheumatic disease is stable, and if appropriate medication adjustments can be made ahead of time.

Platelet function in term and preterm neonates

Platelet dysfunction likely contributes to the pathophysiology of catastrophic hemorrhages in preterm neonates. In vitro studies have demonstrated that platelets of both term and preterm neonates are hyporesponsive to a variety of agonists. In contrast,template bleeding times of term neonates are shorter than those from adults. Very little is known about this and other tests of primary hemostasis in premature and sick neonates in the neonatal intensive care unit (NICU). This article covers the current knowledge of platelet function in preterm and term neonates and review show new agents (such as recombinant thrombopoietin and recombinant factor VIIa) may enhance neonatal platelet function.

Antiplatelet agents for preventing pre-eclampsia and its complications

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a platelet-derived vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, low-dose aspirin in particular, might prevent or delay the development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents when given to women at risk of developing pre-eclampsia.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (September 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2003), EMBASE (1994 to 2003) and we handsearched the congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent during pregnancy. Quasi-random study designs were excluded. Participants were pregnant women considered to be at risk of developing pre-eclampsia. Interventions were any comparisons of an antiplatelet agent (such as low-dose aspirin or dipyridamole) with either placebo or no antiplatelet agent.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trials for inclusion in the review and extracted data. We entered data into the Review Manager software and double checked.

MAIN RESULTS

Fifty-one trials involving 36,500 women are included in this review. There is a 19% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents ((43 trials, 33,439 women; relative risk (RR) 0.81, 95% confidence interval (CI) 0.75 to 0.88); number needed to treat (NNT) 69 (51, 109)).Twenty-eight trials (31,845 women) reported preterm birth. There is a small (7%) reduction in the risk of delivery before 37 completed weeks ((RR 0.93, 95% CI 0.89 to 0.98); NNT 83 (50, 238)). Fetal or neonatal deaths were reported in 38 trials (34,010 women). Overall there is a 16% reduction in baby deaths in the antiplatelet group (RR 0.84, 95% CI 0.74 to 0.96); NNT 227 (128, 909)). Small-for-gestational age babies were reported in 32 trials (24,310 women), with an 8% reduction in risk (RR 0.92, 95% CI 0.85 to 1.00). There were no significant differences between treatment and control groups in any other measures of outcome.

REVIEWER'S CONCLUSIONS

Antiplatelet agents, in this review largely low-dose aspirin, have small-moderate benefits when used for prevention of pre-eclampsia. Further information is required to assess which women are most likely to benefit, when treatment is best started, and at what dose.

Low-dose aspirin in pregnancy: maternal and neonatal aspirin concentrations and neonatal prostanoid formation

OBJECTIVE

To evaluate maternal and neonatal plasma concentrations of acetylsalicylic acid and salicylic acid and the neonatal endogenous prostanoid formation during low-dose aspirin prophylaxis (LDA; 100 mg daily) in pregnant women.

METHODS

Concentrations of acetylsalicylic acid and salicylic acid in maternal plasma after at least 4 weeks of LDA (n = 14) and in umbilical cord plasma of newborns after maternal LDA (n = 7) were determined by gas chromatography-mass spectrometry. Platelet and renal formation of thromboxane A2 and the formation of prostaglandin E2 and prostacyclin were evaluated in vivo by quantification of index metabolites in plasma and urine by gas chromatography-mass spectrometry in neonates after maternal LDA (n = 14) and in a control group.

RESULTS

In the pregnant women, acetylsalicylic acid and salicylic acid concentrations rapidly increased after ingestion of LDA. Acetylsalicylic acid was completely eliminated within 4 hours, whereas salicylic acid was detected with low concentrations at 18 and 21 hours after dosing. In the neonates, acetylsalicylic acid was not detected. Salicylic acid was detected in 1 infant only. Platelet thromboxane A2 formation in the newborn infants was significantly suppressed but recovered within 2 to 3 days after discontinuation of LDA. Renal thromboxane A2 formation and the formation of prostaglandin E2 and prostacyclin were not affected by LDA.

CONCLUSION

In pregnant women who are treated with LDA, acetylsalicylic acid is not completely inactivated in the portal circulation but reaches the uteroplacental circulation and exerts antiplatelet effects in the fetus and newborn.

Use of Antibiotic and Analgesic Drugs during Lactation

During lactation, multiple situations can arise that require maternal pharmacological treatment. Because of the many health advantages of human milk to infants, breast feeding should be interrupted only when the needed drug might be harmful to the nursing child and exposure via the breast milk will be sufficient to pose a risk. Since the majority of drugs have not been shown to cause adverse effects when used during lactation, and even temporary interruption of breast feeding can be difficult for the nursing dyad, decisions regarding maternal medication use during breast feeding should be based on accurate and up-to-date information. This article reviews available data on the most commonly used antibiotics and analgesics. The use of most antibiotics is considered compatible with breast feeding. Penicillins, aminopenicillins, clavulanic acid, cephalosporins, macrolides and metronidazole at dosages at the low end of the recommended dosage range are considered appropriate for use for lactating women. Fluoroquinolones should not be administered as first-line treatment, but if they are indicated, breast feeding should not be interrupted because the risk of adverse effects is low and the risks are justified. Paracetamol (acetaminophen), low-dose aspirin (acetylsalicylic acid) [up to 100 mg/day] and short-term treatment with NSAIDs, codeine, morphine and propoxyphene are considered compatible with breast feeding. Safer alternatives should be considered instead of dipyrone, aspirin at a dosage >100 mg/day and pethidine (meperidine). In the light of the many safe alternatives for pain control, breast-feeding mothers should not be allowed to experience pain or be made to feel that they must choose between analgesia and breast feeding.

Umbilical cord serum levels of thromboxane B2 in term infants of women who participated in a placebo-controlled trial of low-dose aspirin

OBJECTIVE

Our aim was to quantify thromboxane B2 (TXB2) in umbilical cord serum of term infants of nulliparous, low-risk women who were randomly assigned to either placebo or low-dose (60 mg) aspirin (ASA) on a daily basis from 24 weeks' gestation through delivery as part of a randomized clinical trial for prevention of preeclampsia.

METHODS

Umbilical cord sera from 230 singleton, term infants whose mothers were involved in our low-dose ASA trial were assayed for TXB2, the stable metabolite of thromboxane A2, without knowledge of treatment or outcome data. The data were related to assigned treatment group, longitudinal pattern of maternal serum TXB2 levels, and other maternal and newborn characteristics. The data also were analyzed according to whether or not maternal serum levels of TXB2 at 29-31, 34-36, and delivery were reduced > or =50% compared to values prior to initiation of the trial.

RESULTS

Umbilical cord TXB2 levels (ng/ml, mean +/- SE) were significantly lower at term in the ASA group (36.1 +/- 3.3, n = 111) than in the placebo group (56.6 +/- 5.7, n = 119; P = 0.002). Umbilical cord TXB2 levels were correlated to those in maternal serum at delivery in the ASA group (r = 0.3441; P = 0.0005) but not in the placebo group (r = 0.0626; P = 0.53). Regardless of assigned treatment group, infants whose mothers had a > or =50% longitudinal reduction in serum TXB2 had lower umbilical cord TXB2 levels (39.2 +/- 3.6, n = 114) than infants whose mothers had <50% reductions in TXB2 (54.6 +/- 5.9, n = 116; P = 0.027). Birthweights of these infants correlated inversely (r = 0.1678, P = 0.017) with maternal serum TXB2 at delivery but not to umbilical cord TXB2 levels; the best correlation between birthweight and maternal serum TXB2 was noted in pregnancies assigned to receive placebo (r = -0.2558, P = 0.009).

CONCLUSIONS

Umbilical cord serum levels of TXB2 1) are reduced in instances of long-term maternal ingestion of ASA, 2) correlate well with maternal serum levels of TXB2 at delivery when there is evidence for consistent maternal use of ASA, but 3) do not correlate with maternal serum TXB2 levels when there is no evidence for frequent maternal ingestion of cyclooxygenase inhibitors. These data suggest that the capacity for platelet production of TXA2 in fetal and maternal compartments are regulated independently. Finally, there is an inverse relationship between maternal serum TXB2 levels at delivery and birthweight of newborn infants that is most evident among the pregnancies assigned to placebo and also among pregnancies in which there was little evidence to suggest a pattern of cyclooxygenase inhibitor use during pregnancy.

Antiplatelet agents for preventing and treating pre-eclampsia

BACKGROUND

Pre-eclampsia is associated with deficient intravascular production of prostacyclin, a vasodilator, and excessive production of thromboxane, a platelet-derived vasoconstrictor and stimulant of platelet aggregation. These observations led to the hypotheses that antiplatelet agents, and low dose aspirin in particular, might prevent or delay the development of pre-eclampsia.

OBJECTIVES

To assess the effectiveness and safety of antiplatelet agents when given to women at risk of developing pre-eclampsia, and to those with established pre-eclampsia.

SEARCH STRATEGY

This review drew on the search strategy developed for the Pregnancy and Childbirth Group as a whole. The Cochrane Controlled Trials Register was also searched, The Cochrane Library 1999 Issue 1, Embase was searched from 1994-1999 and hand searches were performed of the congress proceedings of the International and European Societies for the Study of Hypertension in Pregnancy.

SELECTION CRITERIA

All randomised trials comparing antiplatelet agents with either placebo or no antiplatelet agent during pregnancy. Quasi random study designs were excluded. Participants were pregnant women considered to be at risk of developing pre-eclampsia, and those with pre-eclampsia before delivery. Women treated postpartum were excluded. Interventions were any comparisons of an antiplatelet agent (such as low dose aspirin or dipyridamole) with either placebo or no antiplatelet agent.

DATA COLLECTION AND ANALYSIS

Assessment of trials for inclusion in the review and extraction of data was performed independently and unblinded by two reviewers. Data were entered into the Review Manager software and double checked.

MAIN RESULTS

Forty two trials involving over 32,000 women were included in this review, with 30,563 women in the prevention trials. There is a 15% reduction in the risk of pre-eclampsia associated with the use of antiplatelet agents [32 trials with 29,331 women; relative risk (RR) 0.85, 95% confidence interval (0.78, 0.92); Number needed to treat (NNT) 89, (59, 167)]. This reduction is regardless of risk status at trial entry or whether a placebo was used, and irrespective of the dose of asprin or gestation at randomisation. Twenty three trials (28,268 women) reported preterm delivery. There is a small (8%) reduction in the risk of delivery before 37 completed weeks [RR 0.92, (0.88, 0.97); NNT 72 (44, 200)]. Baby deaths were reported in 30 trials (30,093 women). Overall there is a 14% reduction in baby deaths in the antiplatelet group [RR 0.86, (0. 75, 0.98); NNT 250 (125, >10000)]. Small for gestational age babies were reported in 25 trials (20,349 women), with no overall difference between the groups, RR 0.92, (0.84, 1.01). There were no significant differences between treatment and control groups in any other measures of outcome. Five trials compared antiplatelet agents with placebo or no antiplatelet agent for the treatment of pre-eclampsia. There are insufficient data for any firm conclusions about the possible effects of these agents when used for treatment of pre-eclampsia.

REVIEWER'S CONCLUSIONS

Antiplatelet agents, in this review largely low dose aspirin, have small-moderate benefits when used for prevention of pre-eclampsia. Further information is required to assess which women are most likely to benefit, when treatment should be started, and at what dose.

Prevention of preeclampsia

Preeclampsia is a multisystem disorder of unknown cause. Efforts to prevent the disease or reduce its incidence have utilized pharmacological intervention as well as dietary supplementation. Recent, large, randomized trials have not shown a benefit from the use of aspirin. Calcium supplementation has also been studied extensively and found to be similarly ineffective in reducing the incidence or severity of preeclampsia in healthy women. The studies regarding the use of magnesium, zinc, and fish oils for the prevention of preeclampsia are fewer in number, but have also found minimal to no benefit. In the same respect, numerous randomized trials have been performed using antihypertensive agents, diuretics, and low-salt diet. Results of these studies have not shown any beneficial effect. Prevention of preeclampsia is unlikely as long as the underlying origin remains unknown.

[Role of non-steroidal anti-inflammatory agents in the perioperative period. Usefulness and limitations]

Nonsteroidal antiinflammatory drugs (NSAIDs), including various chemical families of drugs, inhibit prostaglandin synthesis and act on the central nervous system. Prostaglandins are involved in regulation of regional circulations, cell turn-over in the gastrointestinal tract, and in primary haemostasis. The patterns of action of NSAIDs result in analgesic properties, but also in adverse effects. NSAIDs are increasingly used perioperatively, alone or associated with opioids or local anaesthetics, because of their analgesic and opioid sparing properties. Some of their adverse effects, especially ischaemic acute renal failure and gastrointestinal complications, can be life-threatening, and increased haemorrhagic risk is an issue for spinal or epidural anaesthesia in patients taking aspirin. Safe use of NSAIDs is possible in consideration of contraindications (elderly patient, hypovolaemia, cirrhosis, congestive heart failure, renal failure, active gastrointestinal ulcer, bleeding diathesis, pregnancy), and requires close monitoring of renal function if they must be used in patients at risk for renal failure. NSAIDs are not ulcerogenic in the short-term in healthy subjects. They must be used with caution in patients with a preexisting haemostatic defect or undergoing haemorrhagic surgical procedures.

Deficient thromboxane synthesis and response in platelets from premature infants

In vitro function of cord blood platelets from 35 premature infants (gestational age 32 +/- 3.2 wk) was compared with that of 12 full-term infants and 14 adult control subjects. In comparison with adult platelets, preterm platelets showed impaired aggregation, in response to thrombin, collagen, ADP, and U46619 [a stable analog of thromboxane A2 (TxA2)], and impaired [14C]serotonin secretion in response to collagen and U46619. The production of TxB2 (the stable TxA2 metabolite) in response to collagen was reduced in preterm platelets (30.2 +/- 5.5 ng/mL) compared with full-term (52.7 +/- 12.6 ng/mL) or adult control platelets (132.3 +/- 38.7 ng/mL). The deficient TxB2 production and U46619 response prompted further investigation of TxA2 receptor number and binding characteristics. Immunoblotting using an anti-TxA2 receptor antibody (anti-P2) identified a single, identical 55-kD band in solubilized membranes of control, full-term, and preterm platelets. Flow cytometry using anti-P2 produced histograms that did not differ between adults and neonates. Ligand binding studies using [3H]U46619 were carried out on 10 samples from each group. Scatchard analysis yielded a single class of binding sites with no significant difference among the Kd values (85 +/- 16 versus 99 +/- 12 versus 100 +/- 12 nM) or number of binding sites per platelet (1876 +/- 460 versus 2450 +/- 478 versus 2777 +/- 536) for preterm and full-term infants and adults. Therefore platelets of preterm infants show impaired TxA2 production and response. The poor response is not related to altered binding characteristics of the TxA2 receptor but may lie in the postreceptor signal transduction pathway.

The normalization period of platelet aggregation in newborns

This study was performed to investigate the normalization period of the transient platelet dysfunction of newborns. A total of 43 healthy newborns of healthy mothers who had received no medication for at least 14 days prior to delivery were included in the study. Venous blood samples of 44 healthy volunteer adults were used as control. Platelet aggregation study was performed in whole blood by impedance aggregometry. Collagen or ADP was used as the aggregating agent. In the platelet aggregation studies using collagen, maximum aggregation values in the first three days of life were lower than those of adults (p < 0.001). These lower values were improved and reached adult values between the 5th and 9th day of life. Lower maximum aggregation values were observed in newborns in comparison with those of adults when ADP was used, but the difference was not significant except for 5 microM concentration of ADP. There was no significant difference between the aggregation time of the collagen and ADP groups (p > 0.05). In conclusion, the platelet responses to ADP and collagen were increased in newborns as the age progressed and reached normal levels between 5th and 9th day of life. If platelet dysfunction does exist after the 10th day of life, this finding may be due to either simple prolongation of the physiological phenomenon or platelet disorders.

The pharmacological prevention of pre-eclampsia

The disparate results reported in the literature on the effects of low dose aspirin in preventing pre-eclampsia might be caused by non-compliance in the more recent large trials in low-risk patients. All the earlier small trials were done on identified high-risk patients who consider themselves as patients, as do their doctors. Compliance in these patients will be very high. In fact, the only study in healthy subjects in which aspirin intake was controlled for (Hauth et al 1993) showed a marked reduction in the incidence of pre-eclampsia. However, the recent large trials have demonstrated, without any doubt, that low dose aspirin is not a miracle drug. The combined literature points at a 25% reduction in the incidence of pre-eclampsia in association with the use of aspirin (Collins, 1994). The correct indication for the use of low-dose aspirin appears to be the patient that is at very high risk of developing early-onset (less than 32 weeks gestation) pre-eclampsia. Since early-onset pre-eclampsia can begin at any time after 20 weeks gestation, it is necessary to initiate low-dose aspirin therapy early in pregnancy, preferably at 10-14 weeks gestation. The results of the recent large trials emphasize the need for a reliable, sensitive method of predicting or detecting pre-eclampsia at a very early gestational age (Dekker and Sibai, 1991). Valensise et al (1993) recently confirmed earlier studies (McParland et al, 1990) on the useful combination of uteroplacental Doppler flow velocimetry and aspirin in low-risk primigravidae. Results from current large-scale trials, such as the ECPPA, the BLASP, the WHO Jamaica and the second NICHHD studies, will be available in the near future. The results of especially the second NICHHD study on low-dose aspirin, in more than 2000 high-risk women (previous pre-eclampsia/eclampsia, chronic hypertension, class B to F diabetes or multiple gestation), will hopefully give us a more definitive picture on the potential benificial effects of low-dose aspirin in high-risk patients. The effect of aspirin on placental TXA2 deserves further studies. It might be that the optimal level to inhibit placental TXA2 and lipid peroxide production is actually higher than the minimal effective doses of aspirin that are needed to inhibit platelet TXA2 production (Walsh, 1994). Low-dose aspirin appears to be safe for the fetus and neonate. If there is an increased risk of abruptio placentae, this risk appears to be minimal. The final word on the use of low-dose aspirin has not yet been reached; however, we may be getting closer to profiling patients for whom the therapy may be efficacious and beneficial to both mother and fetus. Further studies are also necessary on combinations of aspirin and other antithrombotic drugs, such as heparin or ketanserin (Tanaka et al, 1993; Bolte et al, 1994; North et al, 1994). North et al (1994) demonstrated that treatment of women with severe renal disease with heparin plus aspirin reduced the prevalence of superimposed pre-eclampsia, compared with no treatment or aspirin alone. Next to low-dose aspirin, there appear to be several new and promising pharmaceutical approaches for reducing the consequences of EC dysfunction. Among these are selective TXA2-synthetase or TXA2-receptor antagonists, Serotonin2-receptor blockers, stable PGI2 analogues and NO donors.

Neonatal and maternal platelet cytosolic calcium in normotensive and hypertensive pregnancies

A prospective study investigated platelet cytosolic calcium in non-pregnant volunteers (n = 30) and samples from the umbilical veins of babies from both normotensive (n = 18) and hypertensive (n = 15) primigravidae, and their mothers. There was no significant difference between the neonatal umbilical venous platelet cytosolic calcium concentration (p[Ca2+]i) in babies born to normotensive primigravidae or to those whose pregnancies were complicated by gestational hypertension (88 x 9 (SE) 2 x 5) in normotensive primagravidae, 80 x 6 (2 x 8) in pregnancy induced hypertension without proteinuria, and 89 x 3 (3 x 2) nmol/l in pre-eclampsia. There was also no significant difference in the p[Ca2+]i from the umbilical veins of the pregnancies studied and those of non-pregnant female volunteers in the follicular phase of their menstrual cycle. This was despite a gradual and significant rise in p[Ca2+]i with increasing severity of disease in the mothers of the babies studied (119 x 9 (4 x 1) in normotensive primagravidae, 130 x 8 (7 x 3) in pregnancy induced hypertension without proteinuria, and 148 x 2 (4 x 5 ) nmol/l in pre-eclampsia). The mean maternal p[Ca2+]i in the three samples returned to concentrations comparable with those in non-pregnant subjects by 12 weeks after birth. These data demonstrate no significant difference between the mean p[Ca2+]i in non-pregnant women and those obtained from the umbilical venous blood of normotensive or hypertensive primigravidae. They suggest that the functional hypoactivity of neonatal platelets is probably not secondary to a decrease in basal p[Ca2+]i. They also suggest that the progressively raised p[Ca2+]i in normal and hypertensive pregnancies might be due to a pregnancy specific factor that does not cross the placenta,