[Pregnancy outcomes of 194 couples with balanced translocations]

To investigate the pregnancy outcomes of couples with either maternal or paternal balanced translocations.

One hundred and ninety-four couples were divided into three groups based on the kind of translocations: 135 with reciprocal translocation, 52 with nonhomologous Robertsonian translocations, and 7 with homologous Robertsonian translocations. Past reproductive histories were surveyed. For those who wanted to have their own babies by natural conceptions after knowing their karyotypes as well as the risks of abnormal offsprings, subsequent pregnancy outcomes were recorded. Total pregnancy outcomes were compared between three groups.

(1) 503 previous and subsequent pregnancies were recorded in detail. The pregnancy outcomes are as follows: spontaneous abortions 81.7% (411/503); induced terminations because of fetal abnormalities 3.2% (16/503); birth defects 7.2% (36/503); normal/balanced offsprings 8.0% (40/503). In reciprocal translocations, nonhomologous Robertsonian translocations and homologous Robertsonian translocations, the birth defects rates were 5.7% (20/350), 10.9% (14/128) and 8.0% (2/25), respectively (P < 0.05). The rates of normal/balanced offsprings in each group were 6.6% (23/350), 13.28% (17/128) and 0, respectively (P < 0.05). The rates of spontaneous abortions as well as the rates of induced terminations among three groups had no statistical differences. (2) Among the 52 congenital defects, induced terminations accounted for 30.8% (16/52), and liveborn 69% (36/52). Cytogenetic analyses were performed for 27 congenital defects and Down's syndrome occupied 59% (16/27). (3) 39 couples with reciprocal or nonhomologous Robertsonian translocations gave birth to 40 normal/balanced offsprings, of which 26 were karyotyped: normal karyotypes were 6 (23%) and balanced translocations 20 (77%). Couples with homologous Robertsonian translocations had no normal/balanced offspring.

Balanced translocation carriers suffer from poor pregnancy prognosis. Couples with homologous Robertsonian translocations have little chance to give birth to normal/balanced offsprings.