Efficiency of first-trimester growth restriction and low pregnancy-associated plasma protein-A in predicting small for gestational age at delivery.

OBJECTIVE

To evaluate the efficiency of first-trimester fetal growth restriction (FGR), low pregnancy-associated plasma protein A (PAPP-A), and their combination for predicting small for gestational age (SGA) at delivery.

METHODS

Retrospective cohort study of women undergoing first-trimester aneuploidy screening. Fetal crown-rump lengths (CRLs) were at 10 to 14 weeks' gestation and converted to gestational age adjusted Z-scores. Low PAPP-A was defined as levels<5th percentile for GA. Receiver-operating characteristic curves were used to assess screening efficiencies.

RESULTS

Among 3269 pregnancies meeting the inclusion criteria 185 (5.7%) infants were SGA. CRL Z-score< -1.0 standard deviation was identified as the optimal definition of early FGR. Using either CRL Z-score< -1.0 standard deviation or PAPP-A<5th percentile had the highest sensitivity (33%) with a specificity of 82.1% when screening for SGA. Using a combination resulted in an increased association (adjusted odds ratio 4.23[confidence interval 1.37-13.03]) at the expense of significantly reduced sensitivity (3.13%).

CONCLUSIONS

First-trimester FGR and PAPP-A<5th percentile are associated with delivery of an SGA infant. Neither of these parameters or the combination of the two are sufficient powerful predictors of SGA to be clinically useful screening tools.