A comparison of SMFMS and ISUOG criteria in the prediction of infants with features of growth restriction
By Christopher Owen, NHS Scotland
Correctly identifying a fetus with growth restriction (FGR) remains challenging. Unlike small for gestational age (SGA) fetuses, there is no widely adopted antenatal criteria to diagnose FGR. It is well documented that most adverse outcomes are in growth restricted rather than SGA fetuses.
Our objective was to compare the test performances of 1. Published consensus-based ultrasound criteria (ISUOG) and 2. Published SMFMS ultrasound criteria in the diagnosis of malnourished newborns.
Methods
Both ISUOG and SMFMS criteria were applied to previously described prospectively collected data from 269 low-risk pregnancies undergoing serial EFW, umbilical artery Doppler and neonatal anthropometric measurements. The ISUOG criteria are 1. Estimated Fetal Weight (EFW) <3rd centile or 2. Two out of three from EFW <10th centile, EFW crossing >50 centiles or umbilical artery pulsatility index (PI) >95th centile. The SMFMS criterion is EFW<10th centile. Neonatal malnourishment (preceding FGR) was determined by a skinfold thickness measurement (SFT) <10th centile. Test performance is reported as sensitivity, specificity, PPV, NPV, +LR and –LR.
Results
ISUOG - Sens 57%, spec 84%, PPV 33%, NPV 93%, LR+ 3.6, LR - 0.51
SMFMS - Sens 68%, spec 78%, PPV 30%, NPV 95%, LR+ 3.1, LR- 0.41
Discussion
There are no published comparisons of the ISUOG and SMFMS criteria of FGR in the prediction of malnourished newborns. The test performances of both criteria are similar and modest with low LR+ results.
As with most tests in obstetric practice, both criteria are useful in ruling out growth restriction (high NPV). A limitation of our study is our inability to calculate the cerebroplacental ratio, a metric included in the ISUOG criteria, so there remains the possibility that our study has underestimated the potential of the ISUOG criteria.