Compare performance of antental growth charts by WHO and INTERGROWTH-21 in Indian population.

INTRODUCTION

Fetal growth is monitored in pregnancies to ensure fetalwell-being and to intervene in the context of maternal or fetal pathology 1-3.  Fetuses that fail to meet their growthpotential in-utero are at risk for adverse antenatal and postnatal events suchas stillbirth, preterm birth, and adverse neonatal and long term healthoutcomes4-7. Therefore, antenatal recognition and monitoring offetal growth is extremely important.

Screening for fetal growth isan important and one of the main purposes of antenatal care. It is done byvarious methods one being serial measurement of fetal size by ultrasound andplotting it against gestational age. To help in clinical management of pregnantwomen, there are several growth charts available like- customised charts or populationbased charts, INTERGROWTH-21 antenatal charts and World Health Organisation (WHO)growth charts. The use of first two types of charts is limited by the fact thatthey are derived from single population from high income countries. Hence, leadto misclassification when applied in low or middle income countries.

WHO and INTERGROWTH-21 provided fetal growth charts for estimatedfetal weights and ultrasound biometric measurements, which were intended forworldwide use. Both were made with a similar aim to design standard growthcharts internationally based on multiple population to be made available forgeneral use. However, the conclusions of both the studies were different.

We are going to compare antenatal growth by plotting biometry on boththese charts and correlating with birth weight and evaluate the performance ofthese charts in our population.

 LACUNAE IN EXISTING KNOWLEDGE

INTERGROWTH-21and WHO both made initial assumption, that there would be no differences internationallyamong countries or racial/ethnic groups in fetal growth with optimal conditionslike nutrition, health, environmental conditions but WHO fetal growth charts showsvariations in different parts of the world while INTERGROWTH-21 showed similarityof all fetal skeletal measurements across the study sites.

Tothe best of our knowledge, there is sparse literature regarding the comparisonof these antenatal growth charts in Indian population.

     REVIEW OF LITERATURE

Fetalgrowth is monitored by several methods like abdominal palpation, symphysio-fundalheight measurement, ultrasound scanning and fetal biometry, and growth charts.

The challenge is to identify these high-riskpregnancies using the most effective screening methods.

Ultrasound estimation of fetal weight before birth iswidely used in clinical practice. And this can be serially plotted on growthcharts for fetal growth monitoring. There are several reference charts aboutfetal growth: customised charts, population based charts, INTERGROWTH-21st 8, 9  and World Health Organizationantenatal growth charts 10. However, each has slightlydifferent research aims that impact interpretation of findings.

The INTERGROWTH andWorld Health Organization Fetal studies had a similar approach of using aprescriptive concept that assumes that under optimal socioeconomic andnutritional conditions all fetuses follow one growth standard regardless ofethnic variations. INTERGROWTH-21 observed that there were no differencesinternationally among countries or racial/ethnic groups in fetal growth whenconditions were optimal. Thus they designed a single growth standard. The WorldHealth Organization Multicentre Growth Reference Study found that fetal growthshowed considerable natural variation by ethnicity and to a smaller extent by maternalage, height, weight, parity, fetal sex.

 Vinod Paul et al in 2003 devised an Indian population based growthchart- National Neonatal Perinatal Dtabase (NNPD charts) and concluded that amajor difference existed in prevalence of SGA when using NNPD charts versusINTERGROWTH-21 charts11.

 P. Acharya in 2010 devised fetal biometry and growth curves for Indianpopulation to prevent over-diagnosis of intrauterine growth retardation, underdiagnosis of fetal macrosomia and correct prediction of fetal age in Indianpopulation12.

 Torvid Kiserud et al in 2016 provided that WHOfetal growth charts for EFW and common ultrasound biometric measurements, andshows variations between different parts of the world. Fetal growth showedconsiderable natural variations, differing significantly between countries. Growthwas influenced by maternal age, height, weight, and parity, and by fetal sex.Similarly, birthweight varied significantly between countries, even afteradjustment for differences in the length of pregnancy10.

 Villar etal in 2014 iinterpreted that fetal growth and newborn length are similar acrossdifferent geographical settings when mothers’ nutritional and health needs aremet, and environmental constraints on growth are low. Therefore these resultsprovide the conceptual frame to create international standards for fetal growth13.

 Papageorghiouet al in 2014 recommend Intergrowth -21 charts can be used as internationalfetal growth standards for the clinical interpretation of routinely takenultrasound measurements and for comparisons across populations8.

 J Villaret al in 2012 presented that  inultrasound screening, use of the charts is likely to result in fewerunnecessary interventions, such as caesarean sections, because of an incorrectdiagnosis of IUGR14.

 Arun S Kinare et al in 2010 hypothesised that significant differenceexisted in patterns of fetal growth in rural Indian cohort and western Europeanpopulation. It concluded that fetal size is smaller in a rural Indianpopulation than in European or urban Indian populations, even in mid pregnancy15.

              AIMS AND OBJECTIVES

 1.    To plot fetal growth using WHO growth charts andINTERGROWTH-21 growth charts.

2.    Compare the growth centiles between WHO growth charts andINTERGROWTH-21 growth charts.

3.    To correlate the above with NNPD birth weight centiles.

MATERIALS AND METHODS

PLACE OF STUDY: The study will beconducted in Department of Obstetrics and Gynaecology, Maulana Azad MedicalCollege & associated Lok Nayak Hospital, New Delhi

 STUDYDESIGN: Prospective observational study

 DURATIONOF STUDY: One year

 STUDYPOPULATION: Pregnant females attending antenatal OPD in LNJP hospital

 INCLUSIONCRITERIA:

Participantswith low risk pregnancy will be invited to participate in the study if:

1.     Singletonpregnancy;

2.     Gestationalage at entry is between up to 16 weeks based on LMP (confirmed by ultrasonography)

3.     Dietaryintake of more than 1800 kcal/day

4.      There is no evidence of long-term medication

5.     There isno evidence in the present pregnancy of congenital disease or fetal anomaly.

  EXCLUSIONCRITERIA:

1.     History ofrecurrent miscarriages

2.      Previouspreterm delivery (*<*37 wk)

3.     PreviousFGR

4.     History ofsmoking cigarettes in the past six months

5.      Used illicit drugs in the past year

6.     Having atleast 1 alcoholic drink per day

 OUTCOMES**:**

1. Percentageof fetuses falling under various centiles in antenatal charts by INTERGROWTH-21and WHO, that is, below 3rd centile, below 10th centile,below 50th centile, below 90th centile, above 90thcentile.

2. UsingNNPD (National Neonatal Perinatal Database) charts for correlating fetal growthcentiles with birth weight centiles.

   SAMPLE****SIZE

•      At 95% confidence level and absolute precision as 45% and standard deviationas 267 by intergrowth chart (Paul V et al)11 sample size wascalculated as 135

•      Formula:

Where,

σ  : Standard deviation

d : Precision

1-   Î±/2 : Desired Confidence level

Considering loss of followup of about 10% andfetal anomaly or fetal demise of about 2-3% the sample size for our study willbe 160.

 METHODOLOGY

Pregnantwomen attending ANC OPD up to 16 weeks period of gestation will beevaluated by history and clinical examination. Women will be fully informedabout the study objectives and procedures. Those women who consent toparticipate in the study will be enrolled into the study. A study proformashall be filled that will include baseline information (age, height, weight,drug history of the patient, dietary history).

     Maternalanthropometry and nutritional assessment: Weight will be measured to thenearest 0.1 kg. Height of the mother will be measured in the standing position.The 24-hour diet recall assessment will be carried out.

Women willbe scanned in the first trimester for the estimation of gestational age byusing reference charts published by Robinson and Fleming16. Reliable information on LMP (confirmed by a measurement ofcrown–rump length/biparietal diameter) will be used as the basis forcalculation of period of gestation (POG). Patients whose LMP and USG CRL/BPDwill have discrepancy of </= 1 week will be included in the study.

 A full morphologicalevaluation (anomaly scan) and biometry (BPD, HC, AC, FL) will be conducted at18–20 weeks following standard practices. Fetuses with major abnormalities willbe excluded from further study.

 The ultrasoundbiometry will be performed at following periods of gestation

20+/-2 weeks, 28+/-2 weeks, 36+/-2 weeks

The followingbiometrical parameters assessed will be-

Biparietaldiameter (BPD)

Headcircumference (HC)

Abdominalcircumference (AC)

Femurlength (FL)

Estimatedfetal weight (EFW)

 Thefetuses in whom anomaly is detected or have intrauterine demise during thecourse of study will be excluded from analysis.

 Assessmentof biometric parameters:

Ultra-soundexamination of fetal biometric parameters will be performed using an ultrasoundmachine with 2-5 MHz trans-abdominal transducer and curvilinear probe.

Trans-abdominalapproach will be used.

Pregnantwomen will be examined with partially full bladder and positioned insupine        position.

The measurement willbe obtained as follows:

•Biparietal Diameter:Measured from the outer-outer (BPD 1) and outer – inner (BPD 2) edges of theparietal bones in a cross-sectional view of the fetal head at the level of thethalami and cavum septum pellucidum or cerebral peduncles. The cerebellum isnot to be included. The measurement should be obtained from an image with themidline echo as close as possible to the horizontal plane with the angle ofinsonation of the ultrasound beam at 90 degrees.

•Head Circumference:Obtained from the same image as BPD as follows. Measurement of occipito-frontaldiameter (OFD) obtained by placing calipers on the outer borders of theoccipital and frontal edges of the skull at the point of the midline of theskull and the ellipse facility will be used to follow the outer perimeter ofthe skull to calculate HC.

•AbdominalCircumference: The sonographer will visualize the transverse section of thefetal abdomen as “close as possible†to circular including the stomach and thejunction of the umbilical vein and portal sinus. The anterior-posterior (A-P)and transverse diameters will be measured with calipers placed on the outerborders of the body outline. The A-P diameter will be measured from the spineat 3’o clock or 9’o clock position to the anterior abdominal wall andtransverse diameter at a right angle to the A-P diameter. The ellipse facilitywill be used to calculate AC as outlined above.

•Femoral Length:Measured from an image of the full femoral shaft in a plane as close aspossible to a right angle to the ultrasound beam. The distal femoral epiphysisis to be excluded

 EFW will be calculatedusing

INTERGROWTH-21: Formula based on HC and AC

Log(EFW) = 5.084820 −54.06633×(AC/100)3 âˆ’ 95.80076×(AC/100)3×log(AC/100) +

3.136370 ×(HC/100) 17

WHO: Based on HC, AC and FL18

Log10 weight = 1.326 − 0.00326AC × FL + 0.0107 HC + 0.0438 AC + 0.158 FL

 The above data will be then plotted on WHOand INTERGROWTH-21 charts simultaneously for each fetus at differentgestational ages.

 Neonatalbirth weight assessment:

Birth weight will be measured at delivery andrecorded. The birth weight will be plotted on NNPD charts to determine thecentiles. The birth weight centiles will be then compared with EFW centiles onboth growth charts.

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STATISTICAL ANALYSIS

·      The collected data will be entered in MS-Excel and then analysed andstatistically evaluated using SPSS version 25.

·      Quantitative data will be expressed by mean and standard deviation andsignificant level of difference between means will be tested by t-test or MannWhitney test.

·      Association will be measured by Spearman Rank   Correlation Coefficient. P-value of<0.05will be considered statistically significant.