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/mm). 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 μm/s; fpSGA, 1807.37 ± 199.89 μm/s), D* (control, 54833.29 ±s 8174.20 μm/s; fpSGA, 52689.20 ± 9420.63 μm/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 μm/s; D*, 48279.82 ± 7497.36 μm/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.