Clinical relevance of diagnosing structural chromosome abnormalities in couples with repeated miscarriage.

BACKGROUND The annual number of parental karyotypes in cases of repeated miscarriage is increasing gradually in The Netherlands. The efficiency of offering parental karyotyping in couples with repeated miscarriage has not been evaluated before, especially not for the group with miscarriages at advanced maternal age. METHODS A historical cohort study and nested case-control study were conducted, including couples with at least two miscarriages. Data were retrieved from medical records and telephone interviews. The obstetric follow-up was recorded for > or =2 years after the parental chromosome analysis. Data were analysed to compare ratios of carrier/non-carrier couples in whom maternal age was > or =36 or <36 years at the second, third or fourth and more miscarriage. A projected prevalence of carrier status of a structural chromosome abnormality was calculated by extrapolating the number of included patients to the original level of the total screening population. RESULTS Forty-one couples with carrier status of a structural chromosome abnormality and 74 couples without carrier status were included. No unbalanced offspring arose after the detection of a structural chromosome abnormality. The risk of being a carrier was not significantly lower (as might be expected) when women were > or =36 years. Ascertainment after two, three, or four and more miscarriages did not change these findings. CONCLUSIONS Karyotyping of 1324 couples ascertained for repeated miscarriage did not yield an unbalanced fetal chromosome pattern after the ascertainment of parental carrier status. In women with advanced maternal age, the frequency of carrier status was not lower than in younger women.