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).