Interpretation
The results of our analyses have immediate clinical utility for
antenatal surveillance of fetal growth. Firstly, the
11th centile as a threshold for the whole population,
regardless of risk assessment, confirms that the conventional
10th centile for SGA remains a useful general
standard. The 15th centile as best cut-off to assess
stillbirth risk in a low risk population (Figure 2) is a new finding and
may be a useful limit for fundal height measurements but requires
further investigation. A similar cut-off has been proposed for the
assessment of risk of neonatal death 32.
Secondly, the observed optimal threshold of the 2.7thcentile in high risk pregnancies would confirm the 3rdcentile line as an appropriate cut-off to indicate the presence of fetal
growth restriction, as proposed in the NHS England guidelines33 and the new GAP care pathway 34.
The recommendation is that a fetus with a weight below
3rd centile should be considered for delivery by 37
weeks, regardless of the results of umbilical artery Doppler
investigation because of its limited effectiveness for the assessment of
growth status late in third trimester 9. Fetuses with
a weight between the 3rd and 10thcentile are also at risk, but delivery can be delayed until 39 weeks if
Doppler indices more suitable for assessment at term (uterine artery and
middle cerebral artery) remain normal. 9,33,34