MRI does not change fetal cardiotocographic parameters

Abstract

The aim of this study was to determine whether magnetic resonance imaging (MRI) has any effect on fetal cardiotocographic (CTG) parameters or movement incidence. Sixteen mothers were examined during the last trimester at 28-39 weeks (mean 33 weeks; SD 4) of gestation due to a suspected fetal anomaly found in antenatal ultrasonography (US). MR imaging was performed using Siemens Magnetom Vision 1.5 T equipment with a 25 mT/m peak gradient amplitude. T2-weighted images were produced with HASTE and TRUE-FISP sequences and T1-weighted images with a 2D FLASH sequence. A four-element phase-array coil was used as the receiver. Before and after MRI-examination, a computerized analysis of the fetal heart rate (FHR) was produced. Basal FHR, short-term variation (STV) and fetal movements were calculated. The mean basal FHR was 136 beats/min (SD 11.6) before, and 133 beats/min (SD 8.9) after (P = 0.158). Short-term variation was in the normal range for both CTG-tracings: mean 9.7 ms (SD 2.7) and 8.8 ms (SD 2.8) (P = 0.196). The median for fetal movements before MRI was 48/h, and after MRI 24.5/h (P = 0.98). MRI at high field strength with powerful gradients did not affect fetal heart activity or movement incidence.