New Sri Lankan Crown Rump Length Chart ()
ABSTRACT
Introduction Accurate pregnancy dating is important for many aspects of obstetric care at individual level as well as
population level. Traditionally, pregnancy dating has done by adding 9 months and 7 days to the last menstrual
period (LMP) using Naegele’s formula. Determination of gestational age by
ultrasound is more precise. Most commonly used parameters are mean sac diameter,
gestation sac volume, crown-rump
length (CRL), biparietal diameter (BPD), head circumference (HC) and femur
length (FL). After 24 weeks, gestational age cannot be accurately determined by ultrasound scans. The
biological variability of CRL is small and growth is very rapid. There are many factors that can affect CRL such as measurement errors, differences in growth rates
between individuals, fetal sex and maternal conditions such as diabetes mellitus. A correctly performed measurement of CRL
is the most accurate way of estimating the gestational age in early
pregnancy from 8 weeks to 13 weeks + 6 days. Objectives Our study aims
were to prepare a new Crown Rump Length chart with Sri Lankan population data
and to compare new CRL chart with existing
intergrowth CRL chart. Method Prospective observational study
with recruitment of subjects by Quota sampling technique was carried out from
April 2015 to March 2016. Spontaneously conceived uncomplicated singleton
pregnancies with normal Body Mass Index (BMI) 18.5 - 23 kg/m2 were
recruited at the time of registration to antenatal care. Consenting woman with
known LMP with regular cycles in preceding 3 months were undergone ultrasound
examination only once at gestational age (GA) ranging from 8 weeks to 13 weeks
+ 6 days. If ultrasound dating was different from LMP dating by more than 5 days in pregnancies with POA
less than 9 weeks and dating differences more than 7 days in pregnancies between 9 weeks and
14 weeks were excluded. Pregnancies complicated with uncertain viability, congenital anomalies
and spontaneous miscarriage were excluded from statistical analysis. Data
collection done with pre-tested interviewer administered form and analysis was
carried out using the Statistical Package for Social Sciences (SPSS) version
21. Results A total of 653 subjects were recruited for the study and 557
turned up for ultrasound dating assessment. Dating discrepancy and multiple
pregnancies excluded 31 subjects, uncertain viability and spontaneous
miscarriage excluded 15 subjects resulting 511 subjects for final statistical
analysis. The mean CRL increased with GA almost linearly from day 56 to 97. Conclusions We have produced new CRL chart based on Sri Lankan data and it can be used
for clinical practice in Sri Lanka. There is no statistically significant
difference between our CRL chart and intergrowth CRL chart.
Share and Cite:
Jayasinghe, K. , Kulatunga, S. and Ratnasiri, U. (2022) New Sri Lankan Crown Rump Length Chart.
Open Journal of Obstetrics and Gynecology,
12, 11-24. doi:
10.4236/ojog.2022.121002.
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