Likelihood of recurrence of Down syndrome in subsequent pregnancy

The likelihood of recurrence of Down syndrome caused by trisomy 21 in subsequent pregnancy is only slightly higher than that associated with maternal age.

If either parent has a balanced translocation of chromosome 21 material (ie rearrangement of chromosome material with no extra or missing parts) the risk of recurrence is much higher. Parents who have trisomy 21 mosaicism have an increased chance of having a child with Down syndrome only if the mosaicism is in the germ line.

It is important to offer genetic counselling before subsequent pregnancies. Parental karyotype will form part of this process. See also Prenatal screening for Down syndrome.

For advice on preconception testing, see the Royal Australian College of General Practitioners (RACGP) guidelines on Genomics in general practice.