Rapid calculation of standardized placental volume at 11 to 13 weeks and the prediction of small for gestational age babies
Collins SL., Stevenson GN., Noble JA., Impey L.
Fetal growth restriction is one of the greatest risk factors for stillbirth. This pilot cohort study examined whether rapid placental volume (PlaV) calculation at 11 to 13 + 6 weeks can predict the small for gestational age (cSGA) baby. Women with singleton pregnancies were recruited (N = 145), a static three-dimensional (3-D) volume was captured, and the placental volume was computed using a semi-automated technique. Regression analysis explored the relationships between customized birth weight, placental quotient (PQ), standardized placental volume (sPlaV), and other predictors of SGA (including pregnancy-associated protein and uterine artery pulsatility index (PI). The results were examined using receiver-operating characteristic (ROC) curve analysis in the total population and then in the 2 subgroups whose members were classified as low risk or high risk at booking. Both PQ and sPlaV were significantly different for cSGA pregnancies compared to appropriate for gestational age (AGA) babies (p = 0.003 and < 0.001, respectively) but only sPlaV was normally distributed. The independent predictors of birth weight (sPlaV, pregnancy associated protein, and nuchal translucency) were combined to produce a predictive model for cSGA. The ROC curves for prediction of cSGA in all 143 women gave areas under the curve of 0.77 (0.66 to 0.87) for sPlaV alone and 0.80 (0.69 to 0.92) for the combined model. When this was applied to the low-risk group, the areas under the curve were 0.82 (0.69 to 0.94) and 0.84 (0.72 to 0.95), respectively. For the high-risk group, the areas under the curve were 0.67 (0.45 to 0.86) for sPlaV alone and 0.76 (0.55 to 0.96) for the combined model. The use of this rapid-image analysis technique and dimensionless index to correct for gestation brings the possibility of an early combined screening test for the cSGA baby a step closer. © 2013 World Federation for Ultrasound in Medicine & Biology.