Does serial 3rd trimester ultrasound improve detection of small for gestational age babies: Comparison of screening policies in 2 European maternity units.

Objective: Methods for the antenatal detection of small for gestational age babies (SGA) differ between countries. The aim of this study was to compare the diagnostic accuracy of routine versus selective small for gestational age babies screening policy using data from two European Maternity Units.

Study Design: This was a retrospective cohort study from Liverpool Women's Hospital, UK, that uses selective third trimester sonography and from the University Hospital Centre Zagreb, Croatia, that uses routine third trimester sonography for SGA detection. Screen positive cases were defined as pregnancies with estimated fetal weight (EFW) <10th centile at the last 3rd trimester scan. True positives had both EFW and birth weight <10th centile. Pregnancy management data and perinatal outcomes were retrieved from hospital electronic data and special care baby unit (SCBU) reports.

Results: The proportion of small for gestational age babies was higher in Liverpool (7.8%) compared with Zagreb (4%); P<0.001. Sensitivity for detection of SGA babies in Zagreb was 27% (95%CI 15%-44%) and 33% (95%CI 23%-45%) in Liverpool. The specificity was high in both centres (Zagreb 100% (95%CI); Liverpool 98% (95%CI)). The induction of labour for antenatally diagnosed SGA babies was more common in Liverpool (38.5%) than in Zagreb (9.1%). In both centres, all antenatally diagnosed SGA babies admitted to SCBU were preterm babies. Their indications for admission to SCBU were complications related to prematurity.

Conclusion: The effectiveness of selective SGA screening policy is comparable to universal third trimester ultrasound screening. Further prospective evaluations of SGA screening policies are warranted and they should include full cost-effectiveness analysis and assessment of possible harm from increased interventions leading to more preterm births.