Reference charts of foetal biometry in Asians.

OBJECTIVES

To construct reference ranges for foetal biometry measurements of biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), humerus length (HL) and mandible length (ML) for the Asian population in Singapore.

DESIGN

A prospective, cross-sectional study.

SETTING

The obstetric ultrasound services and the labour ward of the department of Obstetrics and Gynaecology in Singapore General Hospital.

SUBJECTS

The foetuses of 6,374 women whose delivery date was within 2 weeks of their estimated date of delivery (EDD) as calculated from the last menstrual period.

METHOD

During the period August 1, 1989 and December 31, 1993, 17,005 obstetric ultrasound scans were retrieved from the computerised database. These ultrasound scans were cross-referenced with the delivery database and the earliest ultrasound scan of 6,374 women who delivered within 2 weeks of their EDD were retrieved for analysis. Different growth models were fitted using regression analysis to estimate the mean and standard deviations as functions of gestational age. Centiles were then derived after confirming a normal distribution of measurements at each gestation.

RESULTS

A total of 6,131 measurements of the BPD, 6,117 measurements of the HC, 6,017 measurements of the AC, 6,078 measurements of the FL, 2,863 measurements of the HL and 2,029 measurements of the ML were obtained. Regression analysis using the linear-cubic formula was used to model the mean values; a separate linear regression analysis was used to model the standard deviations.

CONCLUSION

These are the regressed reference charts from 6,374 Asian foetuses using parametric analysis of cross-sectional data. The authors encourage their use in Asian foetuses.