Morphometric and textural analyses of magnetic resonance imaging (MRI) can point out subtle architectural deviations that are associated with fetal growth restriction (FGR) during the second half of pregnancy. The first-time finding hints at the potential to spot otherwise hidden placental woes earlier and intervene in a more timely fashion, a research team led by Children’s National Hospital faculty reports in Pediatric Research.
“We found reduced placental size, as expected, but also determined that the textural metrics are accelerated in FGR when factoring in gestational age, suggesting premature placental aging in FGR,” says Nickie Andescavage, M.D., a neonatologist at Children’s National and the study’s lead author. “While morphometric and textural features can discriminate placental differences between FGR cases with and without Doppler abnormalities, the pattern of affected features differs between these sub-groups. Of note, placental insufficiency with abnormal Doppler findings have significant differences in the signal-intensity metrics, perhaps related to differences of water content within the placenta.”
The placenta, an organ shared by the pregnant woman and the developing fetus, delivers oxygen and nutrients to the developing fetus and ferries away waste products. Placental insufficiency is characterized by a placenta that develops poorly or is damaged, impairing blood flow, and can result in still birth or death shortly after birth. Surviving infants may be born preterm or suffer early brain injury; later in life, they may experience cardiovascular, metabolic or neuropsychiatric problems.
Because there are no available tools to help clinicians identify small but critical changes in placental architecture during pregnancy, placental insufficiency often is found after some damage is already done. Typically, it is discovered when FGR is diagnosed, when a fetus weighs less than 9 of 10 fetuses of the same gestational age.
“There is a growing appreciation for the prenatal origin of some neuropsychiatric disorders that manifest years to decades later. Those nine months of gestation very much define the breath of who we later become as adults,” says Catherine Limperopoulos, Ph.D., director of MRI Research of the Developing Brain at Children’s National and the study’s senior author. “By identifying better biomarkers of fetal distress at an earlier stage in pregnancy and refining our imaging toolkit to detect them, we set the stage to be able to intervene earlier and improve children’s overall outcomes.”
The research team studied 32 healthy pregnancies and compared them with 34 pregnancies complicated by FGR. These women underwent up to two MRIs between 20 weeks to 40 weeks gestation. They also had abdominal circumference, fetal head circumference and fetal femur length measured as well as fetal weight estimated.
In pregnancies complicated by FGR, placentas were smaller, thinner and shorter than uncomplicated pregnancies and had decreased placental volume. Ten of 13 textural and morphometric features that differed between the two groups were associated with absolute birth weight.
“Interestingly, when FGR is diagnosed in the second trimester, placental volume, elongation and thickness are significantly reduced compared with healthy pregnancies, whereas the late-onset of FGR only affects placental volume,” Limperopoulos adds. “We believe with early-onset FGR there is a more significant reduction in the developing placental units that is detected by gross measures of size and shape. By the third trimester, the overall shape of the placenta seems to have been well defined so that primarily volume is affected in late-onset FGR.”
In addition to Dr. Andescavage and Limperopoulos, study co-authors include Sonia Dahdouh, Sayali Yewale, Dorothy Bulas, M.D., chief of the Division of Diagnostic Imaging and Radiology, and Biostatistician, Marni Jacobs, Ph.D., MPH, all of Children’s National; Sara Iqbal, of MedStar Washington Hospital Center; and Ahmet Baschat, of Johns Hopkins Center for Fetal Therapy.
Financial support for research described in this post was provided by the National Institutes of Health under award number 1U54HD090257, R01-HL116585, UL1TR000075 and KL2TR000076, and the Clinical-Translational Science Institute-Children’s National.