Abstract

Detection of the small for gestational age (SFGA) or large for gestational age (LFGA) fetus is important because they are associated with poor perinatal outcome. Ultrasound can be used to predict estimated fetal weight (EFW).

A retrospective cohort study was performed using computerised records of all non-diabetic women referred for ultrasound growth scan (USS) with clinically suspected SFGA or LFGA singleton fetuses from 35-week gestation to the Norfolk and Norwich University Hospital between October 2008 and March 2009 (n=185). The study's aim was to determine the accuracy of EFW by ultrasound; the impact of inaccuracy on labour outcomes; and the efficacy of routine antenatal care at identifying SFGA and LFGA fetuses.

The authors calculated expected birth weights (no. days USS to birth ×25 g, Owen et al1) to determine accuracy of USS EFW determination against actual birth weight. The authors identified the number of SFGA and LFGA infants born within this time period to determine detection rates. Intervention rates of labour induction or elective abdominal delivery were collected for our cohort.

The study found that ultrasound EFW is inaccurate. However it did not significantly impact on rates of labour induction. 79% of growth scans were performed on well-grown fetuses. 87% of SFGA and LFGA fetuses were not identified by clinicians during routine antenatal care.