Utility of placental diffusion-weighted magnetic resonance imaging in prenatal diagnosis of small for gestational age infants and pregnancy outcome prediction.

INTRODUCTION

Ultrasound-diagnosed small for gestational age (SGA) has a particular rate of misdiagnosis. We hypothesized that diffusion-weighted magnetic resonance imaging (MRI), specifically intravoxel incoherent motion (IVIM) imaging, could identify false-positive SGA (fpSGA).

METHODS

A prospective study. Placentas were scanned at gestational weeks 28-41 on a 3.0 T MRI using 9 b-values (0-800 s/mm2). Pregnancies were suspected as complicated by SGA when fortnightly ultrasound biometries confirmed that estimated fetal weights (EFW) were <10th percentile, while final birth weight >10th percentile was considered fpSGA. A total of 28 control, 20 fpSGA and 27 SGA patients were included. The mean values of the diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f) were calculated and compared between groups.

RESULTS

In the control and fpSGA groups, D (control, 1866.61 ± 213.74 μm2/s; fpSGA, 1807.37 ± 199.89 μm2/s), D* (control, 54833.29 ±s 8174.20 μm2/s; fpSGA, 52689.20 ± 9420.63 μm2/s) and f (control, 33.31% ± 3.49%; fpSGA, 33.17% ± 2.96%) were similar. However, all three were significantly lower in the SGA group (D, 1664.32 ± 288.53 μm2/s; D*, 48279.82 ± 7497.36 μm2/s; f, 27.53% ± 3.52%) than in the other two groups (p < 0.05). The f was the best parameter in distinguishing the control and SGA groups, and the fpSGA and SGA groups.

DISCUSSION: IVIM analysis might be suitable for the noninvasive identification of fpSGA pregnancies and SGA patients as an important supplement to ultrasound biometry.