INTRODUCTION

Fetal growth is monitored in pregnancies to ensure fetal well-being and to intervene in the context of maternal or fetal pathology ^1-3.  Fetuses that fail to meet their growth potential in-utero are at risk for adverse antenatal and postnatal events such as stillbirth, preterm birth, and adverse neonatal and long term health outcomes^4-7. Therefore, antenatal recognition and monitoring of fetal growth is extremely important.

 Screening for fetal growth is an important and one of the main purposes of antenatal care. It is done by various methods one being serial measurement of fetal size by ultrasound and plotting it against gestational age. To help in clinical management of pregnant women, there are several growth charts available like- customised charts or population based 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 that they are derived from single population from high income countries. Hence, lead to misclassification when applied in low or middle income countries.

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

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

LACUNAE IN EXISTING KNOWLEDGE

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

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

 REVIEW OF LITERATURE

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

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

Ultrasound estimation of fetal weight before birth is widely used in clinical practice. And this can be serially plotted on growth charts for fetal growth monitoring. There are several reference charts about fetal growth: customised charts, population based charts, INTERGROWTH-21^{st 8, 9}  and World Health Organization antenatal growth charts ¹⁰. However, each has slightly different research aims that impact interpretation of findings.

 The INTERGROWTH and World Health Organization Fetal studies had a similar approach of using a prescriptive concept that assumes that under optimal socioeconomic and nutritional conditions all fetuses follow one growth standard regardless of ethnic variations. INTERGROWTH-21 observed that there were no differences internationally among countries or racial/ethnic groups in fetal growth when conditions were optimal. Thus they designed a single growth standard. The World Health Organization Multicentre Growth Reference Study found that fetal growth showed considerable natural variation by ethnicity and to a smaller extent by maternal age, height, weight, parity, fetal sex.

Vinod Paul et al in 2003 devised an Indian population based growth chart- National Neonatal Perinatal Dtabase (NNPD charts) and concluded that a major difference existed in prevalence of SGA when using NNPD charts versus INTERGROWTH-21 charts¹¹.

P. Acharya in 2010 devised fetal biometry and growth curves for Indian population to prevent over-diagnosis of intrauterine growth retardation, under diagnosis of fetal macrosomia and correct prediction of fetal age in Indian population¹².

 Torvid Kiserud et al in 2016 provided that WHO fetal growth charts for EFW and common ultrasound biometric measurements, and shows variations between different parts of the world. Fetal growth showed considerable natural variations, differing significantly between countries. Growth was influenced by maternal age, height, weight, and parity, and by fetal sex. Similarly, birthweight varied significantly between countries, even after adjustment for differences in the length of pregnancy¹⁰.

Villar et al in 2014 iinterpreted that fetal growth and newborn length are similar across different geographical settings when mothers’ nutritional and health needs are met, and environmental constraints on growth are low. Therefore these results provide the conceptual frame to create international standards for fetal growth¹³.

Papageorghiou et al in 2014 recommend Intergrowth -21 charts can be used as international fetal growth standards for the clinical interpretation of routinely taken ultrasound measurements and for comparisons across populations⁸.

J Villar et al in 2012 presented that  in ultrasound screening, use of the charts is likely to result in fewer unnecessary interventions, such as caesarean sections, because of an incorrect diagnosis of IUGR¹⁴.

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

AIMS AND OBJECTIVES

1.     To plot fetal growth using WHO growth charts and INTERGROWTH-21 growth charts.

2.     Compare the growth centiles between WHO growth charts and INTERGROWTH-21 growth charts.

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

MATERIALS AND METHODS

 PLACE OF STUDY: The study will be conducted in Department of Obstetrics and Gynaecology, Maulana Azad Medical College & associated Lok Nayak Hospital, New Delhi

STUDY DESIGN: Prospective observational study

DURATION OF STUDY: One year

STUDY POPULATION: Pregnant females attending antenatal OPD in LNJP hospital

INCLUSION CRITERIA:

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

1.     Singleton pregnancy;

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

3.     Dietary intake of more than 1800 kcal/day

4.      There is no evidence of long-term medication

5.     There is no evidence in the present pregnancy of congenital disease or fetal anomaly.

EXCLUSION CRITERIA:

1.     History of recurrent miscarriages

2.      Previous preterm delivery (<37 wk)

3.     Previous FGR

4.     History of smoking cigarettes in the past six months

5.      Used illicit drugs in the past year

6.     Having at least 1 alcoholic drink per day

                                                            OUTCOMES:

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

2) Using NNPD (National Neonatal Perinatal Database) charts for correlating fetal growth centiles with birth weight centiles.

SAMPLE SIZE

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

•       Formula:

Where,

σ  : Standard deviation

d : Precision

1-    α/2 : Desired Confidence level

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

METHODOLOGY

Pregnant women attending ANC OPD up to 16 weeks period of gestation will be evaluated by history and clinical examination. Women will be fully informed about the study objectives and procedures. Those women who consent to participate in the study will be enrolled into the study. A study proforma shall be filled that will include baseline information (age, height, weight, drug history of the patient, dietary history).

 Maternal anthropometry and nutritional assessment: Weight will be measured to the nearest 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 will be scanned in the first trimester for the estimation of gestational age by using reference charts published by Robinson and Fleming¹⁶. Reliable information on LMP (confirmed by a measurement of crown–rump length/biparietal diameter) will be used as the basis for calculation of period of gestation (POG). Patients whose LMP and USG CRL/BPD will have discrepancy of </= 1 week will be included in the study.

A full morphological evaluation (anomaly scan) and biometry (BPD, HC, AC, FL) will be conducted at 18–20 weeks following standard practices. Fetuses with major abnormalities will be excluded from further study.

 The ultrasound biometry will be performed at following periods of gestation

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

The following biometrical parameters assessed will be-

Biparietal diameter (BPD)

Head circumference (HC)

Abdominal circumference (AC)

Femur length (FL)

Estimated fetal weight (EFW)

The fetuses in whom anomaly is detected or have intrauterine demise during the course of study will be excluded from analysis.

         Assessment of biometric parameters:

Ultra-sound examination of fetal biometric parameters will be performed using an ultrasound machine with 2-5 MHz trans-abdominal transducer and curvilinear probe.

Trans-abdominal approach will be used.

        Pregnant women will be examined with partially full bladder and positioned in supine        position.  

The measurement will be obtained as follows:

•Biparietal Diameter: Measured from the outer-outer (BPD 1) and outer – inner (BPD 2) edges of the parietal bones in a cross-sectional view of the fetal head at the level of the thalami and cavum septum pellucidum or cerebral peduncles. The cerebellum is not to be included. The measurement should be obtained from an image with the midline echo as close as possible to the horizontal plane with the angle of insonation of the ultrasound beam at 90 degrees.

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

•Abdominal Circumference: The sonographer will visualize the transverse section of the fetal abdomen as “close as possible” to circular including the stomach and the junction of the umbilical vein and portal sinus. The anterior-posterior (A-P) and transverse diameters will be measured with calipers placed on the outer borders of the body outline. The A-P diameter will be measured from the spine at 3’o clock or 9’o clock position to the anterior abdominal wall and transverse diameter at a right angle to the A-P diameter. The ellipse facility will be used to calculate AC as outlined above.

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

EFW will be calculated using

          INTERGROWTH-21: Formula based on HC and AC

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

          3.136370 ×(HC/100) ¹⁷

           WHO: Based on HC, AC and FL¹⁸

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

  The above data will be then plotted on WHO and INTERGROWTH-21 charts simultaneously for each fetus at different gestational ages.

Neonatal birth weight assessment:

 Birth weight will be measured at delivery and recorded. The birth weight will be plotted on NNPD charts to determine the centiles. The birth weight centiles will be then compared with EFW centiles on both growth charts.

STATISTICAL ANALYSIS

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

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

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