Down's syndrome was the most common chromosomal abnormality, accounting for 618 cases.

Is it coincidence that they miscarry shortly after the 20-week anomaly scan, when any chromosomal abnormality would be detected?

The cause may be beyond their control (for example, a chromosomal abnormality), but for many it's an indication that they are in poor shape.

She was never diagnosed with any known genetic disorder or chromosomal abnormality that would help explain why.

As many as half the embryos miscarried have a chromosomal abnormality.