Data on families of chromosome translocation carriers ascertained because of habitual spontaneous abortion

A report of nine cases and review of the literature of infertile men carrying balanced translocations involving chromosome 5

Background

Balanced translocations may cause the loss of genetic material at the breakpoints and may result in failure of spermatogenesis. However, carriers of reciprocal translocation may naturally conceive. Genetic counseling of male carriers of translocations remains challenging. This study explores the clinical features of carriers of chromosome 5 translocations, enabling informed genetic counseling of these patients.

Results

Of 82 translocation carriers, 9 (11%) were carriers of a chromosome 5 translocation. One case had azoospermia, while three cases had experienced recurrent spontaneous abortions, two cases had each experienced stillbirth, and three cases produced a phenotypically normal child confirmed by amniocentesis. A literature review identified 106 patients who carried chromosome 5 translocations. The most common chromosome 5 translocation was t(4,5), observed in 13 patients. Breakpoint at 5p15 was observed in 11 patients. All breakpoints at chromosome 5 were associated with gestational infertility.

Conclusion

In genetic counseling, physicians should consider chromosome 5 and its breakpoints. Carriers of chromosome 5 translocations may continue with natural conception or use assisted reproductive technologies, such as preimplantation genetic diagnosis.

A rare case of a mosaic unbalanced translocation after chorionic villous sampling

BACKGROUND

Most of the literature suggests that unbalanced chromosomal translocations may lead to poor obstetrical outcomes. We present a case of an unbalanced translocation resulting in trisomy 1q and partial monosomy 20p identified on chorionic villous sampling (CVS).

METHOD

Case report with expert-derived clinical management and guidance.

RESULTS

After the abnormal CVS result, a subsequent amniocentesis revealed a normal 46,XX fetal karyotype. Detailed second trimester ultrasound of the fetus revealed no gross structural abnormalities. The CVS karyotype results were attributed to confined placental mosaicism (CPM) of the unbalanced translocation. The infant is 18 months old and has normal phenotype and karyotype.

CONCLUSION

We recommend that if CPM with an unbalanced translocation is diagnosed on CVS, parental karyotype and an amniocentesis should be offered in conjunction with genetic counseling. In rare instances, such as this one, an unbalanced translocation may have a favorable outcome.

Analysis of chromosome segregation during preimplantation genetic diagnosis in both male and female translocation heterozygotes

Individuals carrying translocations suffer from reduced fertility or spontaneous abortions and seek help in form of assisted reproductive technology (ART) and preimplantation genetic diagnosis (PGD). While most translocations are relatively easy to detect in metaphase cells, the majority of embryonic cells biopsied in the course of in vitro fertilization (IVF) procedures are in interphase. These nuclei are thus unsuitable for analysis by chromosome banding or painting using fluorescence in situ hybridization (FISH). Thus several methods have been devised to detect translocation imbalance through FISH in single cells for purpose of PGD, among them polar body chromosome painting, interphase FISH with combination of subtelomeric and centromeric probes, breakpoint spanning probes, and cell conversion. Results with PGD indicate a significant decrease in spontaneous abortions, from 81% before PGD to 13% after PGD. They also indicate very high rates of chromosome abnormalities in embryos from translocation carriers, 72% for Robertsonian translocations and 82% for reciprocal translocations. Sperm analysis was found to be a good predictor of IVF and PGD outcome, with samples with more than 60% abnormal forms indicating poor prognosis. Similarly, the predictability from first PGD cycle results for future cycles was 90%. In summary, PGD can help translocation carriers to achieve viable pregnancies, but the success of the process is conversely related to the baseline of unbalanced gametes.

Selective chromosome analysis in couples with two or more miscarriages: case-control study

OBJECTIVE

To identify additional factors, such as maternal age or factors related to previous reproductive outcome or family history, and the corresponding probability of carrying a chromosome abnormality in couples with two or more miscarriages.

DESIGN

Nested case-control study.

SETTING

Six centres for clinical genetics in the Netherlands.

PARTICIPANTS

Couples referred for chromosome analysis after two or more miscarriages in 1992-2000; 279 carrier couples were marked as cases, and 428 non-carrier couples served as controls.

MAIN OUTCOME MEASURES

Independent factors influencing the probability of carrier status and the corresponding probability of carrier status.

RESULTS

Four factors influencing the probability of carrier status could be identified: maternal age at second miscarriage, a history of three or more miscarriages, a history of two or more miscarriages in a brother or sister of either partner, and a history of two or more miscarriages in the parents of either partner. The calculated probability of carrier status in couples referred for chromosome analysis after two or more miscarriages varied between 0.5% and 10.2%.

CONCLUSIONS

The probability of carrier status in couples with two or more miscarriages is modified by additional factors. Selective chromosome analysis would result in a more appropriate referral policy, could decrease the annual number of chromosome analyses, and could therefore lower the costs.

Predictive value of sperm fluorescence in situ hybridization analysis on the outcome of preimplantation genetic diagnosis for translocations

OBJECTIVE

To determine whether the proportion of abnormal sperm is predictive of the proportion of abnormal embryos from couples in which the males are translocation carriers.

DESIGN

Controlled clinical study.

SETTINGS

Private in vitro fertilization (IVF) center.

PATIENT(S)

Eleven cases of reciprocal translocation male carriers.

INTERVENTION(S)

Blood sample and sperm sample collection from each male partner. Embryo biopsy of the embryos produced in each cycle.

MAIN OUTCOME MEASURE(S)

Fluorescence in situ hybridization on lymphocyte slides to characterize each translocation case, then fluorescent in situ hybridization (FISH) with specific probes for each of the sperm samples. Preimplantation genetic diagnosis of the translocations in the 11 cases.

RESULTS

A correlation was found between the percentage of abnormal gametes and the percentage of abnormal embryos, and a predictive equation is proposed for this relationship: A = -55 + (1.9 x B), where A is the percentage of abnormal embryos and B the percentage of abnormal sperm.

CONCLUSION(S)

The predictive value of the sperm analysis was established. Patients with 65% or less chromosomally abnormal sperm have a good chance at conceiving; patients with higher rates would need to produce 10 or more good quality embryos to have reasonable chances of conceiving.

Preimplantation genetic diagnosis of numerical and structural chromosome abnormalities

The causes of the decline in implantation rates observed with increasing maternal age are still a matter for debate. Data from oocyte donation strongly suggest that in women of advanced reproductive age, the ability to become pregnant is largely unaffected while oocyte quality is compromised. The incidence of chromosomal abnormalities in embryos is considerably higher than that reported in spontaneous abortions, suggesting that a sizable percentage of chromosomally abnormal embryos are eliminated before any prenatal diagnosis. Such loss may partly account for the decline in implantation in older women. Because of the correlation between aneuploidy and reduced implantation, it has been postulated that selection of chromosomally normal embryos could reverse this trend. Preimplantation genetic diagnosis (PGD) for aneuploidy had three objectives relevant to the present paper: (i) to increase rates of implantation, (ii) to reduce risks of spontaneous abortion, and (iii) to avoid chromosomally abnormal births. Implantation rates did not increase when only five chromosomes were analysed in blastomeres. With eight chromosomes, a significant increase in implantation was achieved. PGD can significantly reduce the incidence of spontaneous abortion. In our clinic, a significant decrease in spontaneous abortions was found, from 23 to 11% after PGD. Currently in cases diagnosed at Saint Barnabas, 0.8% chromosomally abnormal conceptions have been observed after PGD versus an expected 3.2% in a control age-matched group. It seems clear that PGD reduces the possibility of trisomic conceptions under all conditions. If a couple's main interest is to improve their chances of conceiving (improve implantation), then one should consider maternal age and number of available embryos. Improvements in conception after PGD again increase after 37 years of age with eight or nine probes. Carriers of translocations are at a high risk of miscarriage or chromosomally unbalanced offspring, and a high proportion have secondary infertility. PGD of translocations has been approached through a variety of methods, here reviewed, and has resulted in a significant reduction in spontaneous abortions. However, implantation rates in translocation carriers are directly correlated with the proportion of normal gametes, and male patients with 70% or more unbalanced spermatozoa have great difficulty in achieving pregnancy with PGD.

Pregnancy outcome following ultrasound-detected fetal cardiac activity in women with a history of multiple spontaneous abortions

OBJECTIVE

To determine whether women with two or more previous spontaneous abortions of unknown etiology, by conventional testing criteria, have a different rate of subsequent fetal loss than controls after ultrasonic documentation of fetal cardiac activity.

METHODS

Medical records were reviewed from 185 women with spontaneous abortion of unknown etiology. Of these women, 91.9% were found to have evidence of cellular immunity to trophoblast and were treated with progesterone for immunosuppression. Ultrasound evaluation was obtained at 5-6 weeks' gestation to document fetal cardiac activity. A control group of 63 women was also studied. All women were followed for pregnancy outcome.

RESULTS

A total of 248 pregnancies were identified from the 185 study patients with multiple spontaneous abortions. Fetal cardiac activity was visualized by ultrasound in 209 pregnancies from 171 study subjects; of these, the outcomes of 208 pregnancies were known. The rate of spontaneous abortion after ultrasound documentation of fetal cardiac activity was 22.7%. Neither maternal age nor number of previous losses was associated with an increased incidence of spontaneous abortion following documentation of fetal cardiac activity. The rate of spontaneous abortion in the control group after documentation of fetal cardiac activity was 3.3%.

CONCLUSION

These data may help clinicians give couples who have experienced recurrent pregnancy loss a more realistic prognosis for pregnancy success once fetal cardiac activity has been confirmed.