Thesmallbabyongestationalultrasoundscan DillyO.C.Anumba ConsultantObstetricianandGynaecologist,SubspecialistinFetomaternalMedicine,HonorarySeniorClinicalLecturerinObstetricsand Gynaecology,TheJessopWing,She/eldTeachingHospitalsNHSTrust,TreeRootWalk,She/eldS102SF,UK KEYWORDS smallbaby;fetalgrowth; ultrasound;pregnancy; biophysicalpro¢le Summary Intrauterinefetalgrowthrestrictionisamajorcauseofperinatalmorbid- ityandmortalityindevelopedcountries.Establishingthisdiagnosisisdi/cult.Whenthis problem is eventually identi¢ed, the management of the a¡ected pregnancy is often challenging.Thisisbecause distinguishing the smallbaby thatisconstitutionallynormal, fromthebabywithanintrinsicproblem,orsu¡eringfromplacentalinsu/ciency,isdif- ¢cult.Afteraccuratelyidentifyingthefetusatriskofhypoxiafromuteroplacentalinsu/- ciency, there is the dilemma of determining the optimum time of delivery.The risk of prematuredeliveryhastobeweighedagainsttheriskoffetaldemisefromintrauterine hypoxia.Thisreviewoutlinesthefetalbiometricindicesbywhichthediagnosisofafetus thatis‘smallforgestationalage’ismade.Theplaceofserialscansforfetalbiometry,and the range of functional studies for fetal surveillance are discussed.Factors that should in£uencethetimingofdeliveryarementionedandsomerecentadvancesinfetalsurveil- lancearehighlighted.  c 2002ElsevierScienceLtd INTRODUCTION The majority of perinatal losses occur in babies with birthweightsoflessthan2500g.Asmanyas20^30%of thesebabiesaresmallforgestationalage(SGA),butthe proportionofthesebabiesthataregrowthrestrictedis unknown.Growthrestrictionmaycausefetaldemise in utero,andantenataldiagnosticstrategieshaveevolvedin an attempt to prevent this. Fetal growth restriction (FGR)isassociatedwithanincreaseinperinatalmorbid- ity from prematurity, congenital malformations, meta- bolic problems (hypoglycaemia, and hypothermia) and asphyxia.There is still an excess of adverse outcomes evenwhenfactorsrelatedtoprematurityarecontrolled for. A study in Scotland demonstrated that premature SGAinfantsbornalivehaveamortalityof12%compared with 5% in premature babies of appropriate weight. There is also an increase in long-term neuro-develop- mental sequelae, and the risk of hypertension and dia- betesinlaterlife. Identi¢cation and management of the growth-re- strictedbabyisamajorchallengeforeveryperinatolo- gist. Clinical estimation of fetal size by abdominal palpationisfraughtwithinaccuracies.Objectiveassess- ment by symphysio-fundal height measurement is a poorpredictorofFGR,withasensitivityandspeci¢city of 27% and 88%, respectively. Over the last 20 years, ultrasound has become the major diagnostic tool for FGR.However,di¡erentiatingthenormal,constitution- ally small baby from one that is growth restricted re- mains problematic. Inappropriate premature delivery mayleadtosubstantialneonatalmorbidityandmortal- ity,whilstexpectantmanagementisoftenattheriskof fetaldemise.Thepurposeofantenatalsurveillanceofthe smallbabyistodeterminewhentherisksofcontinuing the pregnancy outweigh those of premature delivery. This determination is di/cult, controversial and often variesfromoneclinicalscenariotoanother. In this review, current options for the diagnosis and managementofthesmallbabyongestationalultrasound areoutlined,andclinicalpracticepointsandfuturere- searcharementioned. DEFINITIONS Theterm‘smallforgestationalage(SGA)’isbasedona statisticalde¢nitionthatincludesallinfantsbornbelow the lower con¢dence limit of a normal curve of birth weightplottedagainstgestationalageatbirthinweeks. Variations in birth weight charts for di¡erent popula- tions,racialgroups,altitudeandfetalgendermeanthat ababyconsideredappropriatelygrownbyonestandard maybeconsideredsmallbyanother.Theidealchartfor eachinstitutionshouldbederivedfromthelocalunse- lectedpopulationofpregnantwomen.De¢nitionsvary anddi¡erentworkersadvocatealowercon¢dencelimit ofthe3rd,5th,or10thcentileorof  1or 2standard Correspondenceto:DOCA.Tel.:+441142268172;Fax:+44114 2268176;E-mail:d.o.c.anumba@she/eld.ac.uk Current Obstetrics & Gynaecology (2002) 12, 286^292  c 2002ElsevierScienceLtd doi:10.1054/ycuog.0276availableonlineathttp://www.idealibrary.comon