Case of the Month: September

Chromosomal Insights into Recurrent Pregnancy Loss: A Case of Trisomy 10

Clinical History:

A couple with G3A3 presented with a history of three consecutive early pregnancy losses.

• G1: Spontaneous abortion at 7 weeks following natural conception in 2024.
• G2: Missed abortion at 6 weeks in 2025, for which D&C was performed. The POC karyotype reportedly showed t(1;20)(q32.1;q11.2).
• G3: Nonviable pregnancy at 6.2 weeks by CRL, with fetal bradycardia noted on a previous ultrasound.

Genetic Investigation:

Maternal karyotyping performed before the second pregnancy loss showed: 45,XX,der(10)t(10;10)(q26;q26).

Following the second abortion, maternal karyotyping was repeated to correlate with the POC finding, as the POC abnormality involved chromosomes 1 and 20, whereas the maternal rearrangement involved chromosome 10. The repeat maternal karyotype again confirmed 45,XX,der(10)t(10;10)(q26;q26). The paternal karyotype was normal. Considering the mismatch in POC and maternal karyotype along with recurrent pregnancy losses, the current POC was evaluated at Greenarray using both karyotyping and CMA.

Current POC Results:

POC Karyotype: Trisomy 10 with a dicentric chromosome 10, observed in all analysed metaphases.

POC CMA: Demonstrated gain of chromosome 10, confirming the chromosome 10 imbalance identified by karyotyping.

Interpretation:

The previous POC finding of t(1;20)(q32.1;q11.2) did not correlate with the repeatedly confirmed maternal chromosome 10 rearrangement and therefore could not be confidently considered the cause of the previous pregnancy loss. A technical or interpretational difference in the original analysis could not be excluded, although a de novo fetal rearrangement could not be completely ruled out. In contrast, the current POC karyotype and CMA were concordant, demonstrating chromosome 10 gain, with karyotype additionally identifying the dicentric chromosome 10. The finding is likely associated with the maternal 45,XX,der(10)t(10;10)(q26;q26) rearrangement, providing a plausible chromosomal explanation for the current pregnancy loss.

Conclusion:

This case highlights the importance of POC genetic testing and correlation with parental karyotyping in recurrent pregnancy loss. The discrepancy between the previous POC finding and maternal karyotype prompted repeat parental evaluation, while the combined use of karyotype and CMA on the current POC provided a concordant and clinically meaningful result. The couple was counselled regarding the increased risk of unbalanced chromosome 10 conceptions. For future pregnancies, prenatal diagnostic testing with CVS/amniocentesis and CMA ± karyotype, or PGT-SR, may be considered. Overall, genetic testing helped move the couple from an uncertain explanation for their previous pregnancy loss to a more coherent chromosomal diagnosis in the current loss, while also providing information that can guide recurrence-risk counselling and future reproductive planning.