Table 2.

Screening effectiveness for selective and universal ultrasonographic screening for infants who are small and severely small for gestational age

	SGA			Severe SGA
	Yes	No	Total	Yes	No	Total
Selective ultrasonography
EFW <10th	69	69	138	28	110	138
EFW ≥10th or no scan	283	3556	3839	59	3780	3839
Total	352	3625	3977	87	3890	3977
Universal ultrasonography
EFW <10th	199	363	562	67	495	562
EFW ≥10th	153	3262	3415	20	3395	3415
Total	352	3625	3977	87	3890	3977

Selective ultrasonography shows the results of clinically indicated scans. Of the 1666 women selected for ultrasonography at 26 weeks or later, 1388 (83%) had one or two scans, 245 (15%) had three or four scans, and 33 (2%) had five or more scans. If a woman did not have a clinically indicated scan after the routine anomaly scan she was defined as screen negative by selective ultrasonography. Universal ultrasonography shows the results of the last research scan done before birth (either the 28 week scan or the 36 week scan, depending on the gestational age at delivery). Median time interval (IQR) between the last selective scan and birth was 3·1 weeks (1·6–5·6 weeks), and between the last universal scan and birth was 4·1 weeks (3·1–5·0 weeks). SGA=small for gestational age (birthweight <10th percentile; severe SGA birthweight <3rd percentile). EFW=estimated fetal weight (from the last scan before birth).