A mathematical model for evaluation of maternal cell contamination in cultured cells from spontaneous abortions: significance for cytogenetic analysis of prenatal selection factors

Comparative cytogenetics of anembryonic pregnancies and missed abortions in human

Miscarriage is an important problem in human reproduction, affecting 10-15 % of clinically recognized pregnancies. The cases of embryonic death can be divided into missed abortion (MA), for which the ultrasound sign of the embryo death is the absence of cardiac activity, and anembryonic pregnancy (AP) without an embryo in the gestational sac. The aim of this study was to compare the frequency of chromosomal abnormalities in extraembryonic tissues detected by conventional cytogenetic analysis of spontaneous abortions depending on the presence or absence of an embryo. This is a retrospective study of 1551 spontaneous abortions analyzed using GTG-banding from 1990 to 2022 (266 cases of AP and 1285 cases of MA). A comparative analysis of the frequency of chromosomal abnormalities and the distribution of karyotype frequencies depending on the presence of an embryo in the gestational sac was carried out. Statistical analysis was performed using a chi-square test with a p <0.05 significance level. The total frequency of chromosomal abnormalities in the study was 53.6 % (832/1551). The proportion of abnormal karyotypes in the AP and MA groups did not differ significantly and amounted to 57.1 % (152/266) and 52.9 % (680/1285) for AP and MA, respectively (p = 0.209). Sex chromosome aneuploidies and triploidies were significantly less common in the AP group than in the MA group (2.3 % (6/266) vs 6.8 % (88/1285), p = 0.005 and 4.9 % (13/266) vs 8.9 % (114/1285), p = 0.031, respectively). Tetraploidies were registered more frequently in AP compared to MA (12.4 % (33/266) vs. 8.2 % (106/1285), p = 0.031). The sex ratio among abortions with a normal karyotype was 0.54 and 0.74 for AP and MA, respectively. Thus, although the frequencies of some types of chromosomal pathology differ between AP and MA, the total frequency of chromosomal abnormalities in AP is not increased compared to MA, which indicates the need to search for the causes of AP at other levels of the genome organization, including microstructural chromosomal rearrangements, monogenic mutations, imprinting disorders, and epigenetic abnormalities.

Reducing misdiagnosis caused by maternal cell contamination in genetic testing for early pregnancy loss

The analysis of products of conception (POC) is clinically important to establish the cause of early pregnancy loss. Data from such analyses can lead to specific interventions in subsequent natural or assisted conceptions. The techniques available to examine the chromosomal composition of POC have limitations and can give misleading results when maternal cell contamination (MCC) is overlooked. The aim of this study was to develop a protocol for MCC assessment and to formulate POC material handling, testing, and reporting recommendations. Using array comparative genomic hybridization, we tested 86 POC samples, of which 47 sample pairs (DNA extracted from the POC sample and maternal DNA) were assessed for the presence of MCC. MCC was evaluated using an approach we developed, which exploited the genotyping of 14 STR, AMEL, and SRY loci. POC samples showing the clear presence of villi (63.9%) did not contain any signs of the maternal genome and can therefore be reliably tested using conventional methods. The proportion of 46,XX karyotype in the unselected sample batch was 0.39, which fell to 0.23 in visually good samples and was 0.27 in samples having no signs of contamination upon MCC testing. MCC assessment can rescue visually poor samples from being discarded or wrongly genotyped. We demonstrate here that classification based on visual POC material evaluation and MCC testing leads to predictable and reliable POC genetic testing outcomes. Our formulated recommendations covering POC material collection, transportation, primary and secondary processing, as well as the array of pertinent considerations discussed here, can be implemented by laboratories to improve their POC genetic testing practices. We anticipate our protocol for MCC assessment and recommendations will help reduce the misconception regarding the etiology of miscarried fetuses and foster informed decision-making by clinicians and patients dealing with early pregnancy loss.

Karyotype evaluation of repeated abortions in primary and secondary recurrent pregnancy loss

PURPOSE

To study the contribution of embryo chromosomal abnormalities in primary and secondary recurrent pregnancy loss (RPL) and to analyze the recurrence of chromosomal constitution in miscarriages from the same couple.

METHODS

Retrospective study of abortion karyotypes in RPL families based on the mother's primary or secondary RPL status (563 embryo specimens, 335 samples from primary, and 228 samples from secondary RPL). RPL was defined as two or more consecutive miscarriages. One hundred eight cases of recurrent embryo/fetal loss in 51 families were analyzed to assess the probability of having the same karyotype pattern (recurrent normal or recurrent abnormal) in both previous and subsequent pregnancy loss. The karyotypes of abortions were established using standard cytogenetic analysis, as well as interphase fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH).

RESULTS

The frequency of aberrations was 43.9% in abortions from primary RPL versus 52.6% in secondary RPL (p = 0.041). Women 35 years of age or older were the main contributors to this difference. The odds ratio of a subsequent abortion having the same karyotype pattern (normal or abnormal) as the previous one was 6.98 (p = 0.0013).

CONCLUSION

The frequency of abnormalities is higher in abortions from the secondary RPL versus primary RPL group, and this difference is due to the relative deficiency of miscarriages with abnormal karyotypes in older women with primary RPL. The probability of having the same karyotype pattern (recurrent normal or recurrent abnormal) in the previous and subsequent abortion is increased significantly compared with chance.

Comparative Cytogenetic Analysis of Spontaneous Abortions in Recurrent and Sporadic Pregnancy Losses

Background

The majority of miscarriages are sporadic; however, 1–5% of couples experience recurrent pregnancy loss (RPL). Approximately 50–60% of miscarriages result from chromosomal abnormalities. Currently, there are conflicting reports regarding the rates of chromosomal abnormalities between recurrent and sporadic pregnancy losses.

Methods

A retrospective comparative cytogenetic analysis of 442 RPL and 466 sporadic abortions (SA) was performed. Maternal age and medical background were evaluated, and chromosomal abnormality rates were compared between groups.

Results

The frequency of embryos with abnormal karyotypes was significantly higher in SA compared to RPL (56.7 and 46.6%, respectively), and abortions from women under 30 years of age were the main contributor to this difference. An age-dependent increase in the abnormal karyotype rate was observed in two groups of women - those with SA [53.0 and 70.1% for younger and older (≥35-year-old) mothers, respectively] and those with idiopathic RPL without any concomitant reproductive pathology (46.5 and 78.4% for younger and older mothers) - but not in the group of women with RPL associated with concomitant reproductive pathology. The incidence of recurrent abnormal karyotypes in subsequent miscarriages was significantly higher than random probability (odds ratio = 22.75).

Conclusion

Our findings highlight the variability in the risk of aneuploidy in recurrent abortion.

Chromosome distribution of early miscarriages with present or absent embryos: female predominance

PURPOSE

The objective of this study is to compare the chromosomal distribution of early miscarriages with or without embryonic poles.

MATERIALS AND METHODS

It was a retrospective study of 223 women who underwent dilation and curettage (D&C) between 1995 and 2013 for early miscarriages. The presence or absence of a fetal pole was evaluated by abdominal or transvaginal ultrasound. Cytogenetic tests of products of conception following culture were determined in both groups.

RESULTS

Of the 223 early miscarriages, 143 had embryos and 80 did not. The abnormality rate differed significantly (61.5 % vs. 46.3 %, p < 0.05), with trisomy 18, 21 and 45X found only in miscarriages with embryos. There were no significant differences between groups in rates of triploidy, tetraploidy, mosaicism, structure and double abnormality. The female abortus rate was higher in miscarriages with or without embryonic poles, as well as in groups with normal and abnormal karyotypes.

CONCLUSIONS

Chromosome distribution differs in miscarriages with or without embryonic poles. The ultrasound findings might offer different direction to determine the causes of early miscarriages. The higher female abortus rate may be associated with early selection.

Miscarriage chromosome testing: utility of comparative genomic hybridization with reflex microsatellite analysis in preserved miscarriage tissue

OBJECTIVE

To assess the utility of comparative genomic hybridization (CGH) and reflex microsatellite analysis (MSA) for chromosome analysis of preserved miscarriage tissue.

DESIGN

Observational study.

SETTING

Academic recurrent pregnancy loss program.

PATIENT(S)

Patients with recurrent early pregnancy loss, defined as two or more miscarriages at <10 weeks, and at least one preserved miscarriage specimen sent for CGH.

INTERVENTION(S)

Preserved miscarriage specimens were sent for CGH. If results were euploid female (46,XX), reflex MSA was performed to assess if the result was of miscarriage or maternal origin.

MAIN OUTCOME MEASURE(S)

Results were recorded as either informative or uninformative. Uninformative results were classified as "CGH failed" or "maternal contamination."

RESULT(S)

Fifty-eight women with 77 miscarriage specimens met the criteria. CGH failed in nine of the preserved miscarriage specimens owing to minimal pregnancy tissue, and two owing to poor-quality DNA. Twenty-two of the 33 specimens reported as 46,XX by CGH were sent for MSA; maternal contamination was confirmed in 23% (5/22). CGH was therefore informative in 79% (61/77) of the specimens; 64% (39/61) were euploid, and 36% (22/61) were noneuploid, with a 46,XX/46,XY ratio of 2.5.

CONCLUSION(S)

CGH with reflex MSA is useful for obtaining chromosome results in preserved miscarriage specimens, although informative results were achieved in only 79% of specimens. Maternal contamination should be assessed after an initial diploid female result.