Noninvasive prenatal screening and maternal malignancy: role of imaging

Noninvasive prenatal screening (NIPS) tests for fetal chromosomal anomalies through maternal blood sampling. It is becoming widely available and standard of care for pregnant women in many countries. It is performed in the first trimester of pregnancy, usually between 9 and 12 weeks. Fragments of fetal cell-free deoxyribonucleic acid (DNA) floating in maternal plasma are detected and analyzed by this test to assess for chromosomal aberrations. Similarly, maternal tumor-derived cell-free DNA (ctDNA) released from the tumor cells also circulates in the plasma. Hence, the presence of genomic anomalies originating from maternal tumor-derived DNA may be detected on the NIPS-based fetal risk assessment in pregnant patients. Presence of multiple aneuploidies or autosomal monosomies are the most commonly reported NIPS abnormalities detected with occult maternal malignancies. When such results are received, the search for an occult maternal malignancy begins, in which imaging plays a crucial role. The most commonly detected malignancies via NIPS are leukemia, lymphoma, breast and colon cancers. Ultrasound is a reasonable radiation-free modality for imaging during pregnancy, specially when there are localizing symptoms or findings, such as palpable lumps. While there are no consensus guidelines on the imaging evaluation for these patients, when there are no localizing symptoms or clinically palpable findings, whole body MRI is recommended as the radiation-free modality of choice to search for an occult malignancy. Based on clinical symptoms, practice patterns, and available resources, breast ultrasound, chest radiographs, and targeted ultrasound evaluations can also be performed initially or as a follow-up for MRI findings. CT is reserved for exceptional circumstances due to its higher radiation dose. This article intends to increase awareness of this rare but stressful clinical scenario and guide imaging evaluation for occult malignancy detected via NIPS during pregnancy.

MRI safety considerations during pregnancy

The use of magnetic resonance imaging (MRI) during pregnancy is on the rise due its ability to provide detailed cross-sectional anatomy without ionizing radiation. Despite the favorable radiation profile, theoretically concerns regarding the safety of MRI and gadolinium-based contrast agent (GBCA) administration have been raised. Currently there are no studies that have shown any attributable harms of MRI during any trimester of pregnancy although prospective and longitudinal studies are lacking. GBCA administration may be associated with a slightly higher rate of neonatal death, although this is based on a single, large cohort study. Understanding the available evidence regarding MRI safety during pregnancy in the context of current society guidelines will help the radiologist serve as a valuable resource to patients and referring providers.