INTRODUCTION
Low birthweight is one of the three important causes accounting for 78% of all neonatal deaths in India, neonatal infections and birth asphyxia being the other two1. Low birthweight can be consequent to pre-term birth, fetal growth restriction or a constitutionally small baby. Assessment of fetal growth for early diagnosis and timely intervention can reduce the adverse perinatal outcomes associated with growth restricted fetuses.
There are various methods for detection of small for gestational age (SGA) fetuses. Conventionally, it is done by clinical palpation of fundal height. The assessment is based on the relative position of the level of fundal height from an imaginary line passing through the upper border of the umbilicus dividing the abdomen into two parts. Serial ultrasound scans in the third trimester is another tool for early diagnosis of foetal growth disorders2. However, it is not a cost-effective screening tool in low resource settings.
Serial measurement of symphysio-fundal height plotted on customized charts is considered a reliable objective tool for monitoring growth of a fetus3. The International Symphysis Fundal Height Standards Chart by Intergrowth 21st Project study created international standards to measure symphysis fundal height as first level screening tool for foetal growth disturbance4. It also provides a graphical record of the changes in fundal height with the advancement of gestational age and is likely to minimize the subjective variation with the conventional method.
Small for gestational age being an important predictor of poor perinatal outcome, warrants studies to find a simple tool for low resource settings which is cost effective and accurate in early detection of growth restriction.
Hence, the current study was designed to compare the screening accuracy of clinical assessment of fundal height by palpation with symphysio fundal height measurement charted on Intergrowth 21 Project standard charts for early detection of small for gestational age fetuses.
MATERIALS AND METHODS :
Study design and selection criteria: This prospective observational analytic study was conducted in the antenatal clinic and antenatal wards of Department of Obstetrics and Gynaecology, Shrimati Sucheta Kriplani Hospital and Lady Hardinge Medical College, Delhi, India from November 2019 to October 2021.
The study population comprised of 500 pregnant women with singleton pregnancy, with good dating based on regular menstrual cycles and confirmed date of last menstrual period based on foetal crown rump length on ultrasound between 9 to 13 weeks gestation. They were recruited at or beyond 28 weeks of gestation.
Pregnant women with any factor affecting fundal height assessment such as multiple pregnancies, hydramnios, fibroid uterus, uterine malformation, abdominal mass, women with diabetes mellitus or malpresentation were excluded.
Materials: The test tools included:
1. International Symphysis Fundal Height Standards C/hart: The international standard for symphysio fundal height measurement based on serial measurement by prospective longitudinal study from Foetal Growth Longitudinal Study of Intergrowth project4.
2. International Foetal Growth Standards Estimated Foetal Weight Chart: The international foetal growth standards estimated foetal weight chart based on serial ultrasound assessment of foetal anthropometric measurements in pregnant women involved in Foetal Growth Longitudinal Study of 21st Intergrowth project4.
Methodology : Ethical clearance was taken from the Institutional Ethical Committee. All women fulfilling selection criteria were recruited from antenatal clinic and antenatal wards of Lady Hardinge Medical College and Smt. Sucheta Kriplani Hospital in third trimester and serially followed up. Informed consent was obtained from all subjects.
Fundal height (FH) was assessed by the conventional method of palpation by the primary investigator and recorded. For symphysio-fundal height (SFH) measurement, a metric tape of non-elastic material was used. With patient lying supine after voiding the bladder, the upper border of the symphysis pubis was marked, and the 0 cm marking of the metric tape was secured at this point. The tape was then passed in a straight line from the symphysis pubis over to the fundus of the uterus till a resistance was felt on the abdominal wall. The tape was sustained at this point on the fundus of uterus and the measurement was recorded in centimetres as described in Intergrowth 21st study.
Serial SFH measurements were taken during each follow up antenatal visit, and findings were plotted against gestational age in International Symphysis Fundal Height Graph. Any woman with suspected small for gestational age foetus was admitted and managed as per hospital protocol.
Small for gestational age was suspected if,
There was a difference of more than 3 weeks in gestational age assessment by clinical palpation as compared to the calculated period of gestation.
The measured symphysio-fundal height was less than 10th percentile of the standard symphysio-fundal height for that gestational age.
All women were serially followed up with conventional assessment and SFH measurement on each visit till delivery. The birthweight of new-borns was documented and charted on International Foetal Growth Standards Chart from Intergrowth 21st Project. New-born weight less than 10th centile was considered as small for gestational age (SGA).
Sample size estimation: Taking expected proportion of small for gestational age detected by conventional method to be 10%, and proportion of small for gestational age detected by SFH measurement to be 15% and a confidence interval of 95%, sample size was calculated using formula applied for comparison of two proportions
n = (Zα/2 + Zβ)2 * (p1(1-p1) + p2 (1-p2))/ (p1-p2)2
Sample size calculated was 683. For convenience, sample size of 500 was taken.
Statistical analysis : Data entry was done using Microsoft Excel sheet and analysed. Diagnostic accuracy of conventional FH method and SFH measurement was compared by computing sensitivity, specificity, positive predictive value, negative predictive value of the two tests. The 95% confidence interval was calculated wherever applicable. Agreement between the two tests was calculated using kappa statistic (κ).