Babies found to have an AC <3^rd centile at the time of routine anomaly scan should be referred to a fetal medicine specialist within the unit. Serological screening for cytomegalovirus and toxoplasmosis should be offered along with invasive testing for full karyotype and microarray.

The purpose of monitoring is to identify those babies suspected to have FGR and therefore at greater risk of adverse perinatal outcome. Birth timing balances risk of stillbirth against risk of prematurity including adverse outcomes associated with early term birth (37+0 - 38+6wks).

For babies identified as SGA with no features of FGR suitable surveillance is ultrasound every 2wks for biometry, umbilical artery doppler and liqor volume. In the absence of fetal or maternal compromise birth should be offered at 39+0wks. Examples of fetal or maternal compromise include hypertension, reduced fetal movements, reduced liqor volume or abnormal CTG.

For babies identified as early onset FGR, fetal biometry should be performed every 2wks with weekly liqor volume and umbilical artery doppler. If there is absent or reversed EDF prior to 32+0wks then twice weekly doppler should be performed and birth is indicated if the ductus venosus a wave is absent or reversed.

Cardiotocograph (CTG) can be performed from 26+0wks. If computerised CTG is available then short term variability (STV) should be used to guide birth timing. STV <2.6ms between 26+0 and 28+6wks or <3.0ms between 29+0 and 31+6wks indicates birth should be offered as does the presence of persistent unprovoked decelerations at any gestation. Frequency of CTG monitoring will be determined by the individual circumstances.

For babies identified as late onset FGR, fetal biometry should be performed every 2wks with weekly liqor volume and umbilical artery doppler. Middle cerebral artery doppler performed after 34wks gestation may guide timing of birth but further evidence is awaited on this.  

Frequency of CTG monitoring will depend on individual circumstances. If computerised CTG is available then birth is indicated if STV is <3.5ms between 32+0 and 33+6 or < 4.5ms at gestations >34wks, or in the presence of persistent unprovoked decelerations at any time.

Birth is indicated between 32+0 and 33+6wks if the umbilical artery EDF is reversed. Birth >34wks is indicated if umbilical artery EDF is absent or reversed. Early birth may also be indicated by other evidence of fetal compromise such as decreased liqor volume, maternal hypertension or reduced fetal movements.

If monitoring is reassuring then birth can be offered at 37wks for babies with suspected FGR.

A proportion of babies who are growth restricted will not be SGA, particularly those presenting late in the third trimester.

Evidence of reduced growth velocity or “tailing growth”  is defined as a drop of 50 centiles  on sequential scanning for example a drop from the 70^th to the 20^th percentile. This should prompt further ultrasound in two weeks with birth offered at 37wks, earlier if there is evidence of fetal or maternal compromise as outlined above. If EFW falls below 10^th centile or there are abnormal dopplers then ongoing monitoring and birth timing is as for late onset FGR babies.