The potential use of nuclear magnetic resonance imaging in pregnancy

Nuclear magnetic resonance (NMR) imaging is a new technique for in-vivo human imaging. The technique does not use ionizing radiation but employs a radiofrequency pulse and a strong magnetic field to map the hydrogen proton distribution in the body. Since most of the hydrogen in the body is present in either water or fat it is the best imaging method yet devised for displaying the soft tissues of the body. The principles of NMR imaging are briefly described in simple terms for the benefit of the reader not yet familiar with the technique before discussing its potential use in the study of the developing fetus. The absence of ionizing radiation together with the good resolution soft tissue images allow for accurate demonstration of the uterus, placenta and fetus in the pregnant patient. Prior to 22 weeks gestation the fetus may be difficult to image due to its movement during imaging. After 26 weeks the fetus is generally well demonstrated and measurements of fetal size easily made. Observations of the fetal brain, lungs, heart, liver and genito-urinary tract are possible and by measuring the strength of the NMR signal the development of these fetal organs may be made. In the fetus of the diabetic mother measurement of the fetal subcutaneous fat is possible and may be of use in assessing gestational age. The placenta is easily localized even when situated posteriorly. Observations of maternal organs are also possible, especially the kidneys and spine.