Confined Placental Mosaicism Detected With Non‐Invasive Prenatal Testing: Is There an Association Between Mosaic Ratio and Pregnancy Outcome?

Objective: Confined placental mosaicism (CPM) is associated with an increased risk for pregnancy complications, such as fetal growth restriction (FGR), preterm birth and hypertensive disorders. Pregnancies with possible CPM can be identified with non‐invasive prenatal testing (NIPT). We performed a retrospective cohort study to investigate whether the mosaic ratio, as calculated with the Veriseq v2 used for NIPT, can predict adverse pregnancy outcomes in cases of CPM. Method: A mosaic ratio for trisomies detected by NIPT and obstetric data such as fetal growth, structural fetal anomalies and birthweight were retrospectively studied in a cohort of patients with CPM diagnosed between February 2021 and October 2023. Structural and sex chromosomal aberrations were not included in this study. Results: Of 122 CPM cases, 52 cases (42.6%) showed adverse perinatal outcomes, including FGR, low birthweight, hypertensive disorders, or preterm birth. A significantly higher mosaic ratio was found in the adverse outcome group compared to those with normal outcome, but a clear‐cut threshold could not be set, except potentially for trisomy 16. Conclusion: There is an association between the mosaic ratio and adverse pregnancy outcomes in cases of CPM. However, without a clear‐cut threshold, it cannot be used for the individual patient for differentiation between CPM with and without clinical consequences. [ABSTRACT FROM AUTHOR]