JPediatr(RioJ).2015;91(6):603---605
www.jped.com.br
LETTERS
TO
THE
EDITOR
Maternal
hypertension
and
infant
growth
夽Hipertensão
materna
e
crescimento
infantil
DearEditor,
The Jornal de Pediatria published, in its 91st volume, a veryinteresting article entitled:‘‘Growth of pretermlow birthweightinfantsuntil24monthscorrected age:effect of maternal hypertension.’’1 The authors tackled a very
importantissueinthecontextofinfantandmaternalhealth worldwide,mainlyconsideringtheimpactofthegestational periodontheoffspring’shealthanddiseasepatternduring thelife course.However,wewould liketohighlightsome pointsinordertocontributetothissubject.
According to the Task Force on Hypertension in Pregnancy,thehypertensivedisordersinpregnancyare clas-sifiedinto:preeclampsia/eclampsia;chronichypertension; preeclampsia superimposed on chronic hypertension; and gestational hypertension.2 In our unpublished systematic
review,weanalyzed45papers(from2008to2015)onthe association between hypertensive disorders in pregnancy and offspring’s medium- and long-term health outcomes. We found that the high heterogeneity of results among the studies wasmainly caused by different classifications of maternal hypertension, and by the quality of adjust-mentsperformedbytheauthors.Thus,inthisarticle,some methodologicalquestionswereraised.
Firstly,the authorsdefinedtwostudy groupsaccording to the exposure or not to gestational hypertension syn-drome;however,intheirstudydescription,itisnotclearif womenwithchronichypertensionwerealsoincludedinthe hypertensive group. Itis important tohighlight that each hypertensivedisorder hasadifferentandcomplexclinical presentation, withdiverse consequencesin theoffspring. Therefore,itisimportantthatstudiesaddressthe hyperten-sivedisordersindependently(i.e.,chronichypertensionvs. gestationalhypertensionvs.preeclampsia)intheiranalysis.
夽 Please citethisarticleas: PinheiroTV,GoldaniMZ, Bernardi
JR. Maternal hypertension and infant growth.J Pediatr (Rio J). 2015;91:603---4.
Secondly, regarding the sample selection used by the authors,allchildrenincludedinthestudywerebornpreterm (gestationalage<37weeks)andhadlowbirthweight(LBW; 1500gto2499g).ItisknownthatpretermbirthandLBWare abnormalevents,andthepathwaysthatleadtothese con-ditionsaremostlypathological,3 sonormotensive mothers
mustalsohave beenexposedtoadverseconditionsduring pregnancy.Therefore,byrestrictingthesampletopreterm infantswithLBW,theauthorsrendernormotensivemothers agreaterchanceofhavingtheseotheradverseconditions, comparedtotheaveragepopulation.Theoddsratios(OR)of 0.47forinadequateweightand0.20forinadequatelength at24monthsdescribedbytheauthorsreflectthisbias.The protectiveeffectofmaternal hypertensionongrowthwas probablyaresultofunmeasuredcausesofLBWandpreterm birthin thenormotensivegroup. Theseother unmeasured orunknowndisordersmaypossiblyinfluencechildgrowthas muchasmaternalhypertension.
Thirdly,todecreasetheselectionbias,theauthorsshould hadcontrolledtheoutcomeforthecausesofpretermbirth and LBW, such as intrauterine infection, nutritional dis-orders,smoking, alcohol and drugconsumption, violence, lower socioeconomic status, and other chronic diseases. However,theauthorslimitedtheirlogisticregressionmodel to the following variables: gestational age, gender, and adequacyof birth weightfor gestational age; achoice of variablesthat,besides beinginsufficient,maybeasource ofcollisionbias.
In conclusion, cohort studies have great importance in the scientific investigations, and the one conducted by the authors will contribute to this essential field of research.Nonetheless,theanalysisofobservationalstudies isextremelychallengingandmustbecarefullyperformed.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
References
1.Kiy AM, Rugolo LM, De Luca AK, Corrente JE. Growth of pretermlowbirthweightinfantsuntil24monthscorrectedage:
604 LETTERSTOTHEEDITOR
effect of maternal hypertension. J Pediatr (Rio J). 2015;91: 256---62.
2.AmericanCollegeofObstetriciansandGynecologists.TaskForce onHypertensioninPregnancy.Hypertensioninpregnancy.Report of the American College of Obstetricians and Gynecologists’ Task Force on Hypertension in Pregnancy. Obstet Gynecol. 2013;122:1122---31.
3.Greenwood C, Yudkin P, Sellers S, Impey L, Doyle P. Why is there a modifying effect of gestational age on risk factors for cerebralpalsy?Arch DisChild FetalNeonatalEd. 2005;90: F141---6.
TanaraVogelPinheiro,MarceloZubaranGoldani,
JulianaRombaldiBernardi∗
DepartmentofPediatrics,FacultyofMedicine,Hospital deClínicasdePortoAlegre,UniversidadeFederaldoRio GrandedoSul,PortoAlegre,RS,Brazil
∗Correspondingauthor.
E-mail:juliana.bernardi@yahoo.com.br(J.R.Bernardi).
http://dx.doi.org/10.1016/j.jped.2015.07.005
Author’s
reply:
Maternal
hypertension
and
infant
growth
夽Resposta
do
autor:
Hipertensão
materna
e
crescimento
infantil
Weappreciatethecommentsandquestionsaboutourstudy, whichdemonstratesthecarefulandcorrectassessmentthat focused on one aspect of concern in cohort studies: the possibilityofselectionbias.1
We will use this opportunity of scientific discussion to clarifysomemethodologicalaspectsofthestudyandits limi-tations,ensuringitsexternalvalidityandhelpingtoincrease knowledgeonthistopic,stillscarcelystudiedinourcountry: lowbirth-weightpretermgrowth---theeffectofmaternal hypertension.
Thefirstaspecttobediscussedreferstomaternal hyper-tension classification, which in our study was performed usingthecriteriaoftheNationalHighBloodPressure Edu-cation Program Working Group on High BloodPressure in Pregnancy.2 As shown in thefirst paragraphof theresults
section,preeclampsia wasthe predominantmanifestation inthegroupofhypertensivewomen,correspondingto80% (n=63),whichisclassicallydescribedintheliterature.3The
remaining20%ofthisgrouphadgestationalhypertension.No pregnantwomanhadchronichypertension.
Thesecondaspectisthesubjectofmuchdiscussioninthe literature:whatwouldbetheidealcontrolgroupinstudies onprognosisofpreterminfants?
In development studies, it is important to assess the damage in premature infants in relation to the general population.4 In relation to growth, this comparison is
obtainedbytheanalysisoftheZ-scoresofanthropometric measurements.
DOIofreferstoarticle:
http://dx.doi.org/10.1016/j.jped.2015.07.005
夽 Pleasecitethisarticleas:KiyAM,RugoloLM.Author’s reply:
Maternal hypertension and infant growth. J Pediatr (Rio J). 2015;91:604---5.
Our objective was to analyze the growth pattern of lowbirth weightpreterminfants andtheeffectof mater-nal hypertension, using a cohort study design. Thus, the groups were formed based on the exposure or not to maternalhypertensivesyndrome,excludingcasesof multi-plepregnancies,infection/congenitalmalformations,which areclassicfactorsassociatedwithgrowthalterations.The neonatal characteristics were similar between groups, as well asthepost-natal factorsthatareknowntoinfluence growth, such as morbidity and dietary patterns. Logistic regressionmodelswereconstructedtocontrolforpossible confoundingfactors.
Althoughthe selection of a controlgroup consisting of preterminfantsmaylimitresultinterpretation,wedonot considerthat theyshould beattributed toselection bias. The data obtained allowed us to answer the study ques-tionontheeffectofmaternalhypertensiononthegrowth of preterm low birth-weight infants: there were no risk or protective effects.Also,twoimportantandpotentially avoidablerisk factorswerehighlighted: adequacyof birth weightandgrowthinthefirstyearoflife,whichare clini-callyrelevantaspectsthatcontributetoguidetheobstetric andpediatricconductindailypractice.
Regardingthethirdquestion,theauthorsconsiderthat there is a low possibility of selection bias, as the study sample size consisted of a population treated at the Brazilian Unified Health System, quite homogeneous in socio-demographic characteristics, which did not differ betweenthetwoassessedgroups.Smokingwasinfrequent, observed in10% of hypertensive and20% ofnormotensive women(p=0.103).Itisnecessary tohighlight twoaspects ofmethodologicalrigorin ourstudy:controloftheeffect oftimeontheevolutionofanthropometricmeasurements, andpostnatal nutritionassessment,which isan important growthmodulatingfactorinthefirstyearsoflife.5
Finally,weexpectthattheaspectsdiscussedhereincan contribute toimprove theinterpretation ofourstudy and encouragenewstudiestoinvestigateotherfactorsthatcan influencegrowthinlowbirthweightpreterminfants.
Conflicts
of
interest
LETTERSTOTHEEDITOR 605
References
1.Grimes DA,Schulz KF. Cohort studies: marching towards out-comes.Lancet.2002;359:341---5.
2.Report oftheNationalHighBloodPressureEducationProgram WorkingGrouponhighbloodpressureinpregnancy.AmJObstet Gynecol.2000;183:S1---22.
3.Duley L. The global impact of pre-eclampsia and eclampsia. SeminPerinatol.2009;33:130---7.
4.Saigal S, Doyle LW. An overview of mortality and seque-lae of preterm birth from infancy to adulthood. Lancet. 2008;371:261---9.
5.Nzegwu NI, Ehrenkranz RA. Post-discharge nutrition and the VLBWinfant:tosupplementornotsupplement?Areviewofthe currentevidence.ClinPerinatol.2014;41:463---74.
AliceMariaKiya,∗,LigiaMariaSuppodeSouzaRugolob
aNeonatalUnit,HospitaldasClínicas,Faculdadede
MedicinadeBotucatu,UniversidadeEstadualPaulista (UNESP),Botucatu,SP,Brazil
bDepartmentofPediatrics,FaculdadedeMedicinade
Botucatu,UniversidadeEstadualPaulista(UNESP), Botucatu,SP,Brazil
∗Correspondingauthor.
E-mail:alicekiy@zipmail.com.br(A.M.Kiy).
