Mosaicism for structural non-centromeric autosomal rearrangement in prenatal diagnoses: evidence for sex-specific selection against chromosomal abnormalities

Factors affecting clinical manifestation of chromosomal imbalance in carriers of segmental autosomal mosaicism: differential impact of gender

Mosaicism for unbalanced chromosomal rearrangements segmental mosaicism (SM) is rare, both in patients referred for cytogenetic testing and in prenatal diagnoses. In contrast, in preimplantation embryos SM is a frequent finding and, therefore, is even more challenging. However, there is no consistency among results of published studies on the clinical outcomes of embryos with SM, primarily due to the small number of reported cases. Moreover, there is the problem of predicting the potential for the optimal development of a mosaic embryo to a healthy individual. Therefore, we suggested comparing factors predisposing to favorable and poor prognoses, identified in postnatal and prenatal cohorts of SM carriers, with those obtained from studies on preimplantation embryos. We analyzed 580 published cases of SM including (i) postnatally diagnosed affected carriers, (ii) clinically asymptomatic carriers, (iii) prenatally diagnosed carriers, and (iv) miscarriages. We observed a concordance with preimplantation diagnoses regarding the clinical significance of the extent of mosaicism as well as a predominance of deletions over other types of rearrangements. However, there is no concordance regarding excessive involvement of chromosomes 1, 5, and 9 in unbalanced rearrangements and a preferential involvement of larger chromosomes compared to short ones. Paternal age was not found to be associated with SM in postnatally disease-defined individuals. We have identified maternal age and preferential involvement of chromosome 18 in rearrangements associated with clinical manifestations. Male predominance was found among normal pregnancy outcomes and among disease-defined carriers of rearrangements resulting in a gain of genomic material. Female predominance was found among abnormal pregnancy outcomes, among disease-defined carriers of loss and gain/loss rearrangements, and among transmitting carriers of gonadal SM, both affected and asymptomatic. According to data obtained from “post-embryo” studies, clinical manifestations of chromosomal imbalance are associated with a high proportion of abnormal cells, female gender, the type of rearrangement and involved chromosome(s), and maternal age. We believe these data are instructive in the challenging medical genetic counseling of parents faced with no option other than transfer of an embryo with segmental mosaicism.

Recurrent Medical Termination of Pregnancy, Not Always the Same Pathology

OBJECTIVE

Recurrence of termination of pregnancy (TOP) due to fetal or maternal pathology is an uncommon event, and not always related to the same pathology. We aimed to evaluate the indications leading to recurrent TOP and associated risk factors.

MATERIALS AND METHODS

Retrospective study of the recurrent cases of TOP conducted between January 2002 and December 2018.

RESULTS

A recurrence rate of 2.5% was found in a cohort of 693 women submitted to TOP (17/693). Among the paired cases of recurrent TOP, 65% (11/17) were consequent to a different indication, whereas 35% (6/17) were due to the same cause, mainly related to monogenic diseases. TOP related to chromosomopathy was significantly associated with higher maternal and gestational age.

CONCLUSIONS

Most of recurrent cases of TOP do not seem related to the same cause. The occurrence of a monogenic disease or polymalformative syndrome should raise the suspicion of recurrence due to the same pathology.

The Value of Prenatal Systematic Ultrasonic Examination of Fetal Structural Abnormality in Diagnosing Fetal Structural Abnormality

In order to explore the value of prenatal systematic ultrasound examination of fetal structural abnormality in the diagnosis of fetal structural abnormality, this paper retrospectively analyzed 200 cases of fetal abnormality referrals from December 2017 to December 2019 in the prenatal systematic ultrasound examination of the designated hospital in this study of pregnant women. By sorting, summarizing and summarizing the actual conditions of the systematic ultrasound examination of each prenatal fetal abnormal section, this study calculated, recorded and analyzed the detection rate, missed diagnosis rate, sensitivity, and specificity of the systematic ultrasound examination of structural abnormality, and then discussed the value of prenatal systematic ultrasound in the diagnosis of fetal structural abnormality. The results showed that, 185 cases were detected out of 200 fetal abnormality with the detection rate of 92.5%; missed diagnosis rate is 7.3%; detection sensitivity is 87.43%; and specificity is 76.58%. Among them, the detection rate of malformations of different diseases from high to low is cardiovascular system (97.54%), nervous system (93.16%), respiratory system (90.62%), facial system (87.54%), and urinary system (85.47%). Therefore, the prenatal systematic ultrasound fetal structural abnormality examination for pregnant women can achieve good diagnostic results, can provide pregnant women with fetal structural abnormality the opportunity to terminate pregnancy early, and effectively reduce the birth of structural abnormal fetuses and the burden of family and society, having important clinical significance and reducing.

Higher male prevalence of chromosomal mosaicism detected by amniocentesis

OBJECTIVE

To present the calculated frequencies, male to female sex-ratio, and modes of ascertainments in different levels of chromosomal mosaicism (CM) detected at amniocentesis.

MATERIALS AND METHODS

This's a 10-years retrospective study between January 2008 and December 2017 and there were 13,752 cases of amniocentesis performed in MacKay Memorial Hospital, Taipei, Taiwan. Eight hundred and thirty four cases of CM were collected in this study. We reviewed their types of chromosomal abnormalities of mosaicism, the modes of ascertainment (including: advanced maternal age, abnormal ultrasound findings, abnormal maternal serum screening result, and other reasons), maternal age, gestational age at amniocentesis, fetal gender, and perinatal findings. After amniocentesis, in situ culture was performed and the results of karyotype with CM were divided in to three levels.

RESULTS

In our sample of 13,752 amniocentesis, 834 cases with all levels of CM were collected in this study. Of them, there were 562 cases (4.09%) with level I mosaicism, 207 cases (1.51%) of level II mosaicism, and 65 cases (0.47%) of level III mosaicism (Table 1). In the group of advanced of maternal age (AMA), their calculated frequencies, 4.18% in level I, 1.46% in level II and 0.41% in level III, were very similar to those in total cases (p value = 0.206) without statistical significance. In the group of abnormal ultrasound findings, the calculated frequency was much higher in level III (0.87%), however, there was no statistical significance because of the small numbers of level III. In our cases of amniocentesis, the case numbers of male case (50.20%) is very similar to female (49.80%), and the male to female ratio was 1.01. But, we found more cases of male with CM (444 cases) than female (390 cases). The sex-ratio in different levels' calculated frequencies of CM showed similar in level I, and male prevalence was found in level II and III with statistical significance (p value = 0.022). The male prevalence also revealed in both numerical and structural abnormalities in level II and level III, but no difference in the cases of level I.

CONCLUSION

In conclusion, our observation showed a novel finding of higher male prevalence of CM in level II and III, and both in numerical and structural abnormalities. It's consistent with the theory of better survival in male embryo after partial self-correction of initial chromosomal aberrations, male-specific selection against chromosomal abnormalities.