Title

Significant variance exists between customised and Hadlock

estimated fetal weight charts.

Objective

Ascertain if 100% compliance was achieved on plotting the estimated fetal weight (EFW) on

the Customized Growth Chart (GROW 2.0, Perinatal institute).

Design

Retrospective audit of CGC documentation to allow completeness of data collection.

Methods

Data were retrospectively collected from 49 consecutive singleton births over a one-week

period (22nd to 29th November 2024) in our maternity unit (West Midlands, Annual birth rate

~7400, Level 3 NICU facilities). Only live born pregnancies with a 1st trimester estimated due

date ascertained by ultrasound scan and without congenital anomalies were included. EFW

was calculated using Hadlock’s formula using the head circumference, abdominal

circumference and femur length. The EFW (g) was manually entered into GROW 2.0 by clinical

staff. Data were analysed using Microsoft Excel (Windows 365), and Graphpad Prism 5.0 for

Windows.Results

A total of 153 growth scans were undertaken in 49 women (mean 3, Range: 1-5). 65% were

not of white ethnicity- the most common ethnic minority group were women who identified

as Pakistani (27%, 13/79) ethnicity. The median BMI was 28.2 (IQR 23.3-32.7kg/m2). Scan

reported EFWs were transcribed to the GROW 2.0 in all instances.

However, our audit identified a discrepancy between the Hadlock calculated EFW (Median

50.5%, IQR 29.5-68.3) compared with GROW 2.0 (median 60.2%, IQR 38.1-80.8, Wilcoxon

matched-pairs signed rank p <0.0001). This discrepancy was more prominent when analyses

were restricted to BAME women: median EFW 52.0% (Hadlock, IQR 28.5-63.8) vs 65.0%

[GROW 2.0, (IQR 45-84.3), Wilcoxon matched-pairs signed rank p <0.0001].

10% (4/49) of the women had SGA babies (birthweight <10th centile) and none were identified

as SGA by GROW 2.0, while only one was identified as SGA during the antenatal period by the

Hadlock chart.

Conclusion

1.Although the process of inputting data into GROW 2.0 is manually undertaken in our

unit, this was completed for all patients in this audit.

2.A service evaluation project to evaluate the detection of SGA fetuses is warranted to

assess the clinical impact of using GROW 2.0 given the discrepancy between GROW

2.0 compared with population-based charts.