Effect of Supplementation During Pregnancy With L-Arginine

8/3/2019 Effect of Supplementation During Pregnancy With L-Arginine

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RESEARCH

Effect of supplementation during pregnancy with L-arginineand antioxidantvitamins inmedical foodonpre-eclampsia inhigh risk population: randomised controlled trialFelipe Vadillo-Ortega, professor,1 Otilia Perichart-Perera, titular researcher,2 Salvador Espino, associateprofessorof obstetrics andgynaecology,2 Marco Antonio Avila-Vergara, associateprofessorof obstetrics andgynaecology,3 Isabel Ibarra, associate professor,4 Roberto Ahued, professor of obstetrics and gynaecology,2

Myrna Godines, associate professor of obstetrics and gynaecology,1 Samuel Parry, associate professor andchiefof division of maternal-fetalmedicine,5 George Macones, Mitchell andElaineYanow professorandheadof obstetrics and gynaceology,5,6 Jerome F Strauss, professor of obstetrics and gynaecology and dean of School of Medicine7

ABSTRACT

Objective To test the hypothesis that a relative deficiencyin L-arginine, the substrate for synthesis of thevasodilatory gas nitric oxide, may be associated with thedevelopment of pre-eclampsia in a population at highrisk.Design Randomised, blinded, placebo controlled clinicaltrial.Setting Tertiary public hospital in Mexico City.Participants Pregnant women with a history of a previous

pregnancy complicated by pre-eclampsia, or pre-eclampsia in a first degree relative, and deemed to be atincreased risk of recurrence of the disease were studiedfrom week 14-32 of gestation and followed until delivery.Interventions Supplementation with a medical food bars containing L-arginine plus antioxidant vitamins,antioxidant vitamins alone, or placebo during pregnancy.Main outcome measure Development of pre-eclampsia/eclampsia.Results 222 women were allocated to the placebo group,228 received L-arginine plus antioxidant vitamins, and222 received antioxidant vitamins alone.Women had 4-8

prenatal visits while receiving the bars. The incidence of pre-eclampsia was reduced significantly ( 2 =19.41;P


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requirements.8 Moreover, pregnancy has beenreported to be a state of relative arginine deficiency,7

imposed by the increased formation of nitric oxide,supporting the adaptive vasodilatation of pregnancy,and use of L-arginine by the fetus.9 Pre-eclampsia isalsoassociated withincreasedconcentrationsof factors

that inhibit nitric oxide production. Concentrations of asymmetric dimethyl arginine, a competitive inhibitorof nitric oxide synthase, are raised in women with pre-eclampsia.10 Concentrations of soluble fms-like tyro-sine kinase 1, which antagonises vascular endothelialgrowth factor dependent activation of nitric oxidesynthase, have alsobeen shownto be increased in pre-eclampsia.11 Endoglin, which impairs activation of nitric oxidesynthasemediatedby transforminggrowthfactor, is also increased.12

In thepast, theroleof nutritioninthedevelopment of pre-eclampsia hasbeen a subjectofconsiderablediscus-sion. Although littleevidenceexists to show thatdietarymanipulations can prevent pre-eclampsia, the notionthat they might moderate the secondary features of thesyndrome remains in favour.13 Substantial experimen-tal data in animals and humans indicate that L-argininecould have a beneficial effect on haemodynamics.14-16

Of particular note, an expanding literature documentsthat administration of L-arginine improves vascularfunction in people with atherosclerosis and peripheralvascular disease.17-20 The oral administration of L-argi-nine to patients with cardiovascular disease has not beenassociated withany significantadverse sideeffects.This includes previous reports in the literature of useof L-arginine in pregnant women. Facchinetti et al andNeri et al infused L-arginine into women whose preg-nancies were complicated by intrauterine growth retar-dation and reported reduced myometrial activity.2122

These observations raised the possibility that supple-mental L-arginine in the diet could provide a source of substrate for nitric oxide synthesis during pregnancy,which could promote vasodilatation. More clinical stu-dies are needed in this area because we have limitedexperience in the use of L-arginine and other nitricoxide donators for preventing pre-eclampsia, as statedin the Cochrane review by Meher and Duley.23 On theother hand, evidence of endothelial damage mediatedby reactive oxygen species has been proposed asanother mechanism of endothelial damage in pre-eclampsia.24-26 Consequently, antioxidants have beenproposed as prophylactic agents for pre-eclampsia andseveral trials withantioxidants including vitaminC andtocopherols in pre-eclampsia have been published.27-29

At the time thisclinical trial wasstarted, insufficient evi-dence existed for us to discard the use of antioxidantsfor preventionof pre-eclampsia. However, recent trialsand Cochrane reviews do not support the use of anti-oxidants for this purpose.3031 We did a three arm clin-ical trial to test the hypothesis that a combination of L-arginine and antioxidant supplementation would

reduce the risk of pre-eclampsia in a high risk popula-tion in Mexico City.

METHODS

Study participantsWe enrolled pregnant women between 14 and32 weeks of gestation at high risk of pre-eclampsiwho were receiving prenatal care at the InstitutoNacional de Perinatologia Isidro Espinosa de losReyes in Mexico City between January 2001 andDecember 2005. We included patients at increasedrisk of pre-eclampsia, which we defined as eithera per-sonal history of pre-eclampsia or pre-eclampsia in afirst degree relative. Eligible participants agreed tohave their prenatal care and delivery at the institutionand provide informed consent. We excluded patientswith multiple gestation, known major fetal anomalies(as defined by ultrasound studies by the fetal medicindepartment), diabetes mellitus or gestational diabetespre-existing hypertension, pre-existing renal diseasecollagen vascular disease, cancer or strong family history of cancer in first degree relatives, and pre-existingmaternal disease needing drug treatment. Weexcluded women with type 2 diabetes, cancer, or astrong family historyof cancer because the angiogeniactions of vascular endothelial growth factor arethought to be mediated, in part, by nitric oxide.32 Allwomen were screened for gestational diabetes at week14 and again at week 24 of gestation, according to thinstitutional protocol. We decided in advance that if awoman was diagnosed as having gestational diabeteafter randomisation she would discontinue taking barsbecause of the aforementioned safety concerns. However, we includedsuch womenin thedataanalysis.Weexcluded patients with autoimmune disease becauseperoxynitrites have been implicated in the pathogen-esis of tissue damage in autoimmune disease.

Recruitment and randomisationStaff of the department of obstetrics reviewed prenatarecords to identify patients who might qualify for thstudy. A history of pre-eclampsia was confirmed byreview of the patient s records, and a family historyof pre-eclampsia was based on patients self report.Gestational age was assessed by last menstrual perioand confirmed by a first trimester ultrasound evalua-tion. The protocol for recruitment included an initialvisit in which suitability for randomisation was evaluated, an invitation to participate was tendered, a com

plete obstetric and nutritional history was taken, andwritten informed consent was obtained. Participantswere randomly assigned to receive one of the threetreatments.Theprincipalinvestigatormadethe assign-ment centrally after the patient had given informedconsent, by using a computer generated code in ran-dom size blocks with concealment of allocation bysealed envelopes.

Each participant in the L-arginine plus antioxidantvitamins group received two bars a day. The averageconsumption of L-arginine in the United States isaround 5.4 g a day,8 so we decided to supplement at least 100% of this amount in the form of an availabl

medical food (Heart Bars, Nellson Nutraceutical, CAUSA).TwoHeart Bars a daydeliver6.6g ofL-arginine

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and antioxidant vitamins.33 Table 1 shows thecompo-sition of the bars used in the study. Participants in theantioxidant vitamins alone group received two bars a day devoid of L-arginine but containing antioxidant vitamins. Participants in the placebo group receivedtwo placebo bars a day devoid of L-arginine and anti-

oxidant vitamins.The bars were packaged in similar envelopes that made them indistinguishable by appearance, andthey were flavoured such that they had the same tasteirrespective of composition. The bars were packed inboxes containing a sufficient supply for five weeks of treatment. Only the principal investigator knew thegroup codes. We asked participants to consume barsuntil the day of delivery. A basal sample of blood wastaken at the randomisation visit, and protein was mea-sured in a 24 hour urine sample before participantsstarted the consumption of bars.

Clinical follow-upParticipants were scheduled for clinical follow-upevery three to four weeks. Each visit from this point included the following: (1) Arterial pressure measure-ment. Measurements of the arterial pressure weremade according to the recommendations of theAmer-ican Heart Association (AHA) using the auscultatorymethod withmercurysphygmomanometers.34 Allstaff collecting arterial pressure measurements were certi-fied by external monitors from the AHA, who madesite visits to the hospital. (2) A sample of 10 mL of venous blood was collected for determination of L-arginine concentration. Plasma was separated and

maintained at 80C until analysis. (3) Participantswere instructed to obtain a 24 hour urine sample the

daybefore the next visit. We assessed urine protein byquantification in 24 hour urine samples with an auto-mated method (DiaSysDiagnostic Systems,Holsheim,Germany).35 (4)To measurecompliance, wegave eachpatient a personaldiary to recordconsumption ofbars,which they brought to every appointment. We also

instructed them to keep the empty envelopes of theconsumed bars, which they also brought back at eachappointment. (5) We offered nutritional education andassessment of nutritional status during pregnancyto allparticipants. We instructed them to avoid the con-sumptionof overthecounterprenatalantioxidant vita-mins and asked about non-study related vitaminingestion at each visit.

End points

We defined pre-eclampsia as hypertension (systolicblood pressure 140 mm Hg, diastolic blood pressure 90 mm Hg, or both) and proteinuria (>300 mg/24

hours) presenting after 20 weeks of gestation inwomen known to be previously normotensive. Wedefined eclampsia as non-epileptic convulsions. Wedefined mild pre-eclampsia as when hypertensionand proteinuria were present but no evidence of sys-temic organ damage was detectable. Severe pre-eclampsia was detected when proteinuria was above2.0 g/24 hours, blood pressure was 160/110 mmHg, or both. We also assessed several neonatal endpoints, including preterm birth (born before 37 weeksof gestation), birth weight, small for gestational age(according to institutional charts), and Apgar scores.

Webasedthesamplesizecalculationonconsiderationof all three twoway comparisons (placebov antioxidant vitamins alone, placebov antioxidant vitamins plusL-arginine, and antioxidant vitamins plus L-argininev antioxidant vitamins alone), assuming a 50% propor-tional reduction in pre-eclampsia in any group com-pared with placebo, an error of 0.05, a error of 0.2,and a 1:1:1 allocation ratio. We used a Bonferroni cor-rection so that a test specific error () of 0.016 (0.05/3)was used for significance testing of all primary two waycomparisons. We also used the error of 0.016 in oursamplesizeestimation.We assumeda prevalenceofpre-eclampsia in the placebo group of 30% (on the basis ofpilot data from our institution).

L-arginine assays

We measured L-arginine concentrations by high per-formance liquid chromatography after derivatisationwith the o-phthalaldehyde-ethanethiol reagent asdescribed by Lundsjo et al.36 The derivatised sampleswere separatedby using a reversed phase Kingsorb 3C18column (Phenomenex,Torrace,CA)accordingtothe standard method. We used peak areas for quantifi-cation of L-arginine concentrations, using an externalstandard as reference. We report values asM inplasma. We monitored within assay and between

assay coefficients of variation and maintained themunder 3%.

Table 1 | Composition of Heart Bar

Compound Content

Total fat 2.0 g

Saturated fat 0.5 g

Polyunsaturated fat 1.0 g

Monounsaturated fat 0.5 g

Trans fat 0 g

Cholesterol 10 mg

Sodium 65 mg

Potassium 100 mg Total carbohydrate 19 g

Dietary fibre 1.0 g

Sugars 12.0 g

Protein 9.0 g

L-arginine 3.3 g

Vitamin C 250 mg

Vitamin E 200 UI

Niacin 25 mg

Vitamin B-6 2.0 mg

Vitamin B-12 4.8 g

Folate 200 g

Each bar weighed 35 g and contained 534 kJ (130 kcal); bars for placebogroup were devoid of L-arginine and antioxidant vitamins; bars for antioxidant vitamins group were devoid of L-arginine.

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Statistical analysis

The Universidad Autonoma de Sinaloa (MAA-V) andour biostatistics group (SE and MG) did an indepen-dent analysis of the data. The analysis was based onan intention to treat principle. We compared baselinemeasures among the treatment groups by using analy-sis of variance methods and Kruskal-Wallis tests. Wecalculated the proportion of participants who devel-oped pre-eclampsia in each treatment group and didan overall test of equivalence in these proportions byusing a Pearson 2 statistic test. We calculated absoluterisk reduction and relative risk, including 95% confi-dence intervals, and statistical significance.37

RESULTS

We approached 696 women (figure. We excluded 24women because they failed to meet inclusion criteria (10 patients) or refused to participate (14 women). Sixhundred and seventy-two women met our eligibilitycriteria and agreed to participate. Forty-four (6.5%)

women had a direct relative who had developed pre-eclampsia, and they were equally distributed amongthe three arms in this study. Six hundred and twenty-eight women had a previous pregnancy complicatedby pre-eclampsia. We allocated 222women to thepla-cebo group, 228 women received the L-arginine plus

antioxidant vitamins bars, and 222 women receivedthe bars with antioxidant vitamins alone. The treat-ment groups were well balanced with regards to baseline characteristics (table 2).

Clinical follow-up was similar among the womenincluded in the analysis. All groups had a median of (range 2-9) visits during the study (Kruskal-WallisP =0.21). Less than 5% of study visits were missed foall three groups. In terms of compliance, the placebogroup consumed a mean of 1.1 (SD 0.5) bars a day, theL-arginine plus antioxidant vitamins group consumed1.2 (0.4) bars a day, and the vitamins alone group consumed 1.1 (0.43) bars a day (analysis of variance

P =

0.23). The nutritionists developed several strategieto promote compliance. Briefly, patients wereinstructedtomixbarswithotherfoodssuchasyoghurt,gelatine, milk shakes, or fruit.

Reported side effects were significantly more frequent in the group consuming L-arginine plus anti-oxidant vitamins bars than in the placebo group,including nausea (P =0.019; absolute risk reduction0.05, 95% confidence interval 0.02 to 0.08; relativrisk 1.25, 1.04 to 1.51); symptoms of dyspepsi(P =0.04; 0.03, 0.01 to 0.06; 1.34, 1.02 to 1.77); dizzness (P =0.039; 0.03, 0.01 to 0.05; 1.42, 1.02 to 1.97palpitations (P =0.019; 0.04, 0.01 to 0.07; 1.36, 1.05 to

1.76); and headache (P =

0.01; 0.06, 0.03 to 0.09; 1.26,1.06 to 1.51). None of these side effects led to a particpant dropping out of the study.

One hundred and twenty-five patients discontinuedtheir assigned treatment. However, we followed themup until the end of pregnancy and included them ana-lytically in the group to which they were randomisedFifty-six women decided to drop out of the studyvoluntarily: 18 in the placebo group, 17 in the L-arginine plus antioxidant vitamins group, and 21 in the

Assessed for eligibility (n=696)

Placebo (n=222)Received allocated intervention (n=222)

L-arginine + vitamins (n=228)Received allocated intervention (n=228)

Antioxidant vitamins (n=222)Received allocated intervention (n=222)

Excluded (n=24):Did not meet inclusion criteria (n=10)Refused to participate (n=14)

Allocation

Lost to follow-up (n=42):Diabetes (n=24)

Discontinued intervention voluntarily (n=18)





Follow-up

Analysed (n=222) Analysed (n=228) Analysed (n=222) Analysis

Flow diagram of trial

Table 2 | Baseline characteristics of participants. Values are means (SD) unless statedotherwise

CharacteristicPlacebo(n=222)

L-arginine+ vitamins

(n=228)

Vitaminsalone

(n=222) P value

Age (years) 28.2 (5.1) 28.0 (6.1) 27.6 (5.5) 0.47*

Gestationalage atenrolment (weeks) 21.1 (4.7) 20.9 (4.6) 21.1 (5.3) 0.84*

Previous gestation with pre-eclampsia/firstdegree relativewith pre-eclampsia

211/11 218/10 209/13 0.65

Median (range) parity 2 (1-9) 2 (1-6) 2 (1-6) 0.09

Median (range) vaginal deliveries 0 (0-5) 0 (0-3) 0 (0-6) 0.42

Median ( range) previous caesarean sections 1 (0-2) 1 (0-3) 1 (0-3) 0.48

Median (range) abortions 0 (0-5) 0 (0-3) 0 (0-2) 0.13

Systolic blood pressureat enrolment (mm Hg) 105.1 (9.8) 105.4 (8.8) 105.6 (8.8) 0.86*

Diastolic blood pressureat enrolment (mm Hg) 68.3(9.1) 67.2 (8.7) 67.6(7.9) 0.40*

Plasma L-arginine ( M) 21.9 (8.5) 22.7 (8.3) 21.9 (9.2) 0.52*

Pre-gestational b ody mass index 26.8 ( 4.9) 27.5 (5.3) 26.1 ( 4.1) 0.28*

Smoked during pregnancy 5 4 6 0.87

*Analysis of variance.Kruskal-Wallis test.

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antioxidant vitamins alone group. Sixty-nine partici-pantsdiscontinued theuse ofbars becauseof thedevel-opment of gestational diabetes: 24 in the placebogroup, 23 in the L-arginine plus antioxidant vitaminsgroup,and22 in theantioxidant vitamins alone group.

Primary end point

Table 3 shows the findings for the primary end point.The incidence of pre-eclampsia/eclampsia was signifi-cantly lower ( 2 =19.41; P


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DISCUSSION

Weobserveda significant reduction in theincidence of pre-eclampsia/eclampsia in pregnant women whoconsumed bars containing L-arginine plus antioxidant vitamins. The results of this trial support the proposedhypothesis that supplemental L-arginine can reducethe risk of pre-eclampsia. Consistent with the mainstudy outcome, a secondary finding of the study wasthat the L-arginine plus antioxidant vitamin supple-mentation resulted in a significant reduction in theriskof indicatedpreterm birthcomparedwithplacebo.

Methodological considerations and strengthsEndothelial nitric oxide synthase is constitutivelyexpressed in endothelial cells, and its activity dependson the level of expression of theenzyme, availability of the substrate, andconcentrations of at least three differ-ent inhibitors that have been associated with pre-eclampsia. Synthesis of nitric oxide thus depends onthe circulating concentration of L-arginine, and adap-tive synthesis of nitric oxide in the endothelium islinked to dietary consumption of this amino acid. Ourcentral hypothesis was that impaired vasodilatation inpregnancies complicated by pre-eclampsia could beprevented by supplementation with L-arginine in thediet. The existing literature suggests that L-argininehas direct effects on blood pressure in experimentalanimal models,normal humans, hypertensivepatients,women with pre-eclampsia, and healthy pregnant women.14-22

Consistent with recent research, antioxidant vita-mins alone did not show a statistically significant reduction in the incidence of pre-eclampsia/eclampsia in our study. Adding L-arginine to antioxidant vita-mins resulted in significant protection against thedevelopment of pre-eclampsia/eclampsia. Our trialwas not powered to detect the small difference wefound between the group consuming L-arginine plusantioxidant vitamins and the group consuming barscontaining only vitamins. An intriguing result is that supplementing antioxidant vitamins had a statisticallysignificant effect on reducing mild pre-eclampsia. Thisfinding is not consistent with the pooled results of theother clinical trials of antioxidant vitamins, which donot suggest a benefit from treatment.30 Recently, theNational Institutes of Health s Maternal-Fetal Medi-

cine Units completed a large trial including severalinstitutions in the United States, which reached a simi-lar conclusion.31 In addition,detrimentaleffects of sup-plemental vitamin C and vitamin E during gestationhave been reported.303839

Limitations of studyThe intervention used in this study must be evaluatedin a population of pregnant women at low risk of pre-eclampsia. This is particularly relevant because wefounda highprevalenceof recurrenceofpre-eclampsia in the studied population. Unfortunately, no informa-tion is availablefrom other Mexican centres that could

helpto identifycharacteristicsassociated withthishighrecurrence rate compared with centres in other

countries that have reported lower recurrence of pre-eclampsia.4041

At the time we started this clinical trial, no othecommercial presentation for L-arginine was availableother than supplemented bars. However, new pro-ducts containing the amino acid L-arginine in a more

palatablepresentationareemerging. This makes it fea-sible topropose a population basedstudy ofL-argininesupplementation in larger groups of women with different levels of risk for pre-eclampsia. We did noinclude a study arm that consumed only L-arginine,as the producer could not supply such bars. In addi-tion, we were aware that L-arginine metabolites mayproduce deleterious free radicals,42 so we consideredthe inclusion of antioxidant vitamins in the same barsto be beneficial.Unfortunately, ourstudydesigncouldnot define the relative contributions of L-arginine andantioxidantvitaminsto thebeneficialeffectof thecom-bination on risk of pre-eclampsia. These ingredients

may have had additive effects, or the interaction mayhave been synergistic. Further studies are needed toclarify these relations. Additionally, our trial was powered to detect a 50% reduction in pre-eclampsia andwas thus not designed to detect smaller differences irisk reduction between L-arginine plus antioxidantvitamins and antioxidant vitamins alone.

We did not find concerning side effects during thesupplementation of bars. However, caution is neededin women with peptic ulcer disease, as administrationof L-arginine may worsen their symptoms.

Theprotectiveeffect forpre-eclampsiamay begreat-est if L-arginine and antioxidant vitamins are supple

mented before 24 weeks of gestation. Although ourstudy design did not allow a rigorous test of time osupplementation and outcome, the above noted trendshould be considered in the design of future clinicatrials to evaluate the efficacy of L-argininesupplementation.

Study in context of previous studiesPrevious attempts to use L-arginine during pregnancywere designed to modify the course of established disease, using the amino acid as a hypotensive agent.43

Staff et al showed no effect of L-arginine on cliniccourse when used in women with pre-eclampsia

beyond 28 weeks of gestation.44

This is in concert with our findings, in which women who started treatment beyond 24 weeks of gestation did not seem tobenefit from treatment. Another clinical trial showedno benefits of arginine supplementation once the disease was established.45 However, preliminary evi-dence indicates that supplementing L-arginine duringpregnancy may reduce the risk of pre-eclampsia. Germain et al disclosed some initial findings in women ahigh risk of pre-eclampsia who received L-argininefrom week 10 of gestation.46 A small clinical trial of L-arginine supplementation in women with chronichypertension that showed some maternal benefit was

publishedafterwesubmittedour work forpublication,supporting the potential benefits of this intervention.47

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30 Rumbold A, Duley L, Crowther CA,Haslam RR. Antioxidants for preventingpre-eclampsia. Cochrane Database Syst Rev 2008;1:CD004227.

31 Roberts JM, Myatt L,Spong CY, ThomEA, Hauth JC, LevenoKJ, etal.VitaminsC and E to prevent complications of pregnancy-associatedhypertension. N EnglJ Med 2010;362:1282-91.

32 Papapetropoulos A, Garcia-Carde a G,MadriJA, Sessa WC. Nitricoxide productioncontributesto theangiogenicpropertiesof vascular endothelial growth factor in human endothelial cells. J Clin Invest

1997;100:3131-9.33 MaxwellAJ, AndersonBE, Cooke JP.Nutritionaltherapyfor peripheralarterialdisease:a double-blind,placebo-controlled, randomizedtrial of HeartBar. Vasc Med 2000;5:11-9.

34 Pickering TG, HallJE, Appel LJ, Falkner BE, Graves J,HillMN,et al.Recommendations for blood pressure measurement in humans andexperimental animals. Part1: blood pressuremeasurement inhumans: a statement for professionals and public educationof theAmericanHeart Association Council on High Blood PressureResearch. Hypertension 2005;45:142-61.

35 Orsonneau J, Douet P, Massoubre C, LustenbergerP, Bernard S. Animprovedpirogallol re-molybdatemethodfor determining total urineprotein. ClinChem 1989;35:2233-6.

36 Lundsjo A, HagelbergS, Palmer K, LindbladBS. Amino acid profilesby HPLCafter filter paper sampling: appropriate technology for monitoring of nutritional status. Clin Chim Acta 1990;191:201-10.

37 LevineM,Walter S,Lee H,HainesT, HolbrookA, PharmD, etal.User sguides to themedicalliterature. IV:how to usean article about harm. JAMA1994;271:1615-9.

38 PodmoreID, GriffithsHR, Herbert KE,Mistry N, MistryP, Lunec J.Vitamin C exhibitspro-oxidant properties. Nature 1998;392:559.

39 Banerjee S, ChambersA, Campbell S. Is vitamin E a safe prophylaxisfor pre-eclampsia? Am J Obstet Gynecol 2006;194:1228-33.

40 Hnat MD,Sibai BM,CaritisS, HauhtJ, Lindheimer MD,MacPherson C,et al. Perinatal outcome in women with recurrent pre-eclampsiacomparedwith women whodevelop pre-eclampsiaas nulliparas Am J Obstet Gynecol 2002;186,422-6.

41 Hjartardottir S, LeifssonB, GeirssonR, Steinhorsdottir V. Recurrenceof hypertensivedisorder in second pregnancy. Am J ObstetGynecol2006;194:916-20.

42 RubboH, Radi R,TrujilloM, Telleri R,KalyanaramanB, BarnesS, etal.Nitric oxide regulation of superoxide and peroxynitrite-dependentlipidperoxidation: formation of novel nitrogen-containing oxidizedlipid derivatives. J BiolChem 1994;269:26066-75.

43 Facchinetti F, Longo M, Piccinni F, Neri I, Volpe A. L-arginine infusionreduces blood pressurein pre-eclampticwomen through nitric oxiderelease. J SocGynecol Investig 1999;4:202-7.

44 Staff AC,BergeL, Haugen G, LorenzenB, Mikkelsen B, Henriksen T.Dietary supplementationwithL-arginine or placebo in women withpre-eclampsia. Acta Obstet Gynecol Scand 2004;83:103-7.

45 RytlewskiK, Olszanecki R, Korbut R, Zdebski Z. Effects of prolongedoralsupplementation with L-arginine on blood pressureand nitricoxidesynthesis in pre-eclampsia. Eur J Clin Invest 2005;35:32-7.

46 Germain AM, Valdez G, RomanikMC, Reyes S. Letter to theeditor:evidence supporting a beneficial role for long termL-argininesupplementation in high-risk pregnancies. Hypertension2004;44:e1.

47 Neri I, Monari F, Sgarbi L, Berardi A, Masellis G, FacchinettiF. L-argininesupplementation in women with chronic hypertension:impact onblood pressureand maternaland neonatalcomplications. J Matern Fetal Neonatal Med 2010;23:1456-60.

Accepted: 28 March 2011

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Effect of Supplementation During Pregnancy With L-Arginine