First-Trimester Uterine Artery Doppler for the Prediction of SGA at Birth: The Great Obstetrical Syndromes Study

Objective: To estimate the role of first-trimester uterine artery pulsatility index (UtA-PI) for the prediction of small-for-gestational age (SGA).

Methods: We conducted a prospective cohort study of nulliparous women with singleton pregnancy (Great Obstetrical Syndromes study). UtA-PI was performed at 11 + 0 to 13 + 6 weeks and was reported in multiple of median (MoM). SGA was defined as birth weight below the 10th percentile and stratified as term or preterm SGA. Receiver operating characteristic curves analyses with their area under the curve (AUC) were used to estimate the predictive values of UtA-PI, alone and UtA-PI combined with maternal characteristics. We computed the detection rate and false-positive rate (FPR) of the SOGC SGA screening guidelines in our population.

Results: Of 4610 participants, SGA was identified in 486 pregnancies (10.3%), including 15 (0.3%) associated with preterm delivery. Compared with unaffected pregnancies, the mean log UtA-PI was significantly higher in term SGA and preterm SGA. The difference between preterm SGA and unaffected pregnancies remains significant after exclusion of SGA without preeclampsia. First-trimester UtA-PI was more predictive of preterm (AUC: 0.89) than term (AUC: 0.60) SGA (P < 0.01). Combined with maternal characteristics, UtA-PI could have predicted 64% of preterm and 20% of term SGA (10% FPR). The SOGC guidelines criteria for early screening of SGA had a detection rate of 21% for a FPR of 21%.

Conclusions: First-trimester UtA-PI can be used to predict SGA, but mainly preterm SGA. The current SOGC guidelines criteria for SGA screening are not efficient in nulliparous women.