Gadolinium contrast freely passes through the placenta, which by the second trimester receives 18-30% of the administered dose. The transferred gadolinium then passes into the fetal circulation where it is excreted into the urinary tract and subsequently into the amniotic fluid. Some of the gadolinium in the amniotic fluid will be reabsorbed by the maternal circulation, while some will be swallowed and reabsorbed through the fetal GI tract. Thus the fetus will receive an appreciable recirculant dose of gadolinium following maternal administration
Some fetal anomalies and intrauterine growth retardation have been observed in the fetuses of pregnant rats given high doses gadolinium contrast over prolonged periods of time. Other studies have not confirmed these results. Several studies documenting the utility of Gd in certain conditions, such as evaluation of placenta accreta and fetal central nervous system abnormalities, have not confirmed any adverse observable effects on the fetus.
Out of caution, however, gadolinium should be avoided in pregnant patients if at all possible, unless the perceived diagnostic value of information obtained exceeds these theoretical risks.