Prenatal Screening for Monosomy X in the First Trimester: A Comparison of a Thai Predictive Model and the Fetal...

This study aimed to evaluate the performance of the first-trimester Fetal Medicine Foundation (FMF) algorithm in predicting monosomy X and compare it with a Thai NT-based model using nuchal translucency (NT) alone or combined with maternal serum markers.

This retrospective study analyzed 6,860 singleton pregnancies screened at 11-13+6 weeks. Monosomy X risk was estimated based on the trisomy 21 risk calculated by the FMF algorithm and Thai logistic regression models based on NT alone, NT with pregnancy-associated plasma protein A (PAPP-A), and NT with PAPP-A and beta-human chorionic gonadotropin (β-hCG).

Thirty cases of monosomy X were identified (0.4%), all of which were confirmed prenatally by invasive diagnostic procedures, including amniocentesis, chorionic villus sampling, or cordocentesis. The Thai model using NT and PAPP-A had the highest area under the receiver operating characteristic curve (AUC) of 0.953, with a sensitivity of 86.7% and a specificity of 94.1%. NT alone also showed strong performance (sensitivity 83.3%, specificity 94.4%). The FMF algorithm achieved the highest specificity (97.9%) but lower sensitivity (53.3%). Adding β-hCG did not improve performance.

NT alone or combined with PAPP-A outperformed the FMF algorithm for monosomy X screening, with NT alone being particularly useful in settings without biochemical testing. The FMF algorithm, while primarily designed for trisomy 21 risk estimation, can also provide monosomy X risk within the same report at no additional cost, which is especially valuable in resource-limited settings where biochemical testing or NIPT is not widely accessible.