The frequency of chromosome aberration in spontaneous and induced abortions in the first three-month period of pregnancy has been presented in this study. The examination has been done in the period from 2001 till 2002 on the sample of 80 chorion and fetal tissue of 8-12 weeks of gestation. The indications for cytogenetic analysis have been the spontaneous abortions (30,0%), fetus mors in utero (46,3%), blighted ovum (3,7%) and induced miscarriage due to anomalies (6,3%) or pathologic genetic screening (13,7%).
Out of 80 analysed fetal tissues, 14 (17,5%) chromosomopathy have been found. The analysis of karyotype of peripheral lymphocyte has been done with parents and three balanced structural aberrations have been determined, which is absolute indication for prenatal cytogenetic analysis of fetal tissues in the following pregnancy.
Related to the age, most of the pregnant women have been younger than 30 years (58,8%). Eight pregnant women have had three pathologic markers of genetic screening on chromosomopathy, nuchal translucency (N.T.), Pregnancy Associated Plasma protein-A (PAPP-A) and free Human Chorionic Gonadotropin (free beta HCG). At seven samples of fetal tissue the chromosome aberration has been confirmed, showing the high security and importance of this screening in the first three-month period of pregnancy.
Key words: spontaneous abortions, chromosome aberrations.
It has been estimated that 50-60% of early spontaneous abortions occur due to chromosome aberration. Polyploidy present about 20% of total number of chromosomopathy, while triploidy are more frequent than tetraploidy. Autosomal trisomy is present with about 52% of total number of chromosome aberration. The most frequent is the trisomy of chromosome 16, present at some 32,3% of chromosomopathy, while trisomy of acrocentric chromosome and chromosome 18 is frequent, as well. Autosomal monosomy is rare, natural selection eliminates them already in the implantation phase of the embryo. The only monosomy present in 17-25% of fetus with chromosome aberration is monosomy of X chromosome.
These assessments of chromosome aberration frequency in miscarried fetus are incomplete and still not examined enough. The Japanese examiners have determined, on the basis of fetal tissue analysis from spontaneous abortions, that the incidence of chromosome aberration is 6,8%. The incidence of clinically not revealed early spontaneous abortions is still not known, but on the basis of some examination it has been estimated to some 33% of embryo.
The aim of work
The aim of the research is to determine the frequency of chromosome aberration in spontaneous abortions of our population.
Method of work
The examination has been done within the period from 2001 till 2002 in the Department for Genetics in Subotica on the sample of 80 spontaneous and induced abortions.
Cytogenetic analysis has been done from chorion and fetal tissue in the first three-month period of pregnancy of 8-12 weeks. The sample of chorionic villus and fetal tissue pulls has been exposed to direct analysis with no cultivation. The cytogenetic analysis of direct material is possible, as the tissue is viable and the cells are dividing spontaneously in cytotrophoblastic layer. In this way the risk of bacterial contamination is less and the results are obtained more quickly.
A genetic anamnesis with genealogy tree and teratogene anamnesis have been taken in the genetic consultation centre for the purpose of determining the beginning risk. The results of ultrasonic and biochemical genetic screening on chromosomopathy in the first three month period of pregnancy, nuchal translucency (N.T.), Pregnancy Associated Plasma protein-A (PAPP-A) and free human chorionic gonadotropin (free-beta-HCG) were correlated with cytogenetic analysis (fetus karyotype).
In the period from 2001 till 2002 in cooperation with Department of Genetics and Department for Gynecology and Obstetrics in Health Centre Subotica, cytogenetic analysis of 80 spontaneous and induced abortions have been done. The samples of chorionic villus and fetal tissue were from non-selective population of pregnant women of various ages in 8-12 week of gestation.
The indication for cytogenetic analysis of tissue sample were the repeated spontaneous abortions, fetus mors in utero, Blighted ovum and induced miscarriage due to ultrasonically registered anomalies. The genetic screening has been done in Subotica from 1999. with each pregnant woman at first three month period, by determination of three markers on chromosomopathy, ultrasonic –N.T. and two biochemical –PAPP-A/free-beta-HCG, in maternal serum. In eight pregnant women all the three markers were pathologic with software processing of individual MOMs the level of chromosomopathy detection security has been estimated at 97%, so upon determination for miscarriage of the pregnant woman, the karyotypisation of the fetal tissue has been done for the correlation with genetic screening.
Out of 80 analysed fetal tissues, 14 (17,5%) chromosome aberrations have been found. We have done cytogenetic examination of these couples, karyotypisation from peripheral lymphocytes, aiming to find the carriers of balanced structural changes of chromosomes (translocation, inversion and other). At three couples we have found balancing of structural aberration, and mothers have been the carriers in all the three cases, which is an absolute indication for choriocentesis or amniocentesis in the following pregnancy, with karyotypisation of fetal cells.
Table 1. The indications for cytogenetic analysis of chorionic villus sampling.
Table 2. Chromosome aberration in spontaneous and induced abortions in relation to the age of pregnant woman and week of gestation
Table 3. Chromosome aberration of fetus and karyotype of parents
Table 4. The karyotype of fetus in relation to the value of MOM biochemical markers and N.T. at pathologic result of pregnancy in the first three-month period
With our sample of 80 cytogenetic analysed chorionic villus and fetal tissues of spontaneous and induced abortions in the first three-month period of pregnancy, 14 (17,5%) chromosome aberration have been found. The most frequent has been the trisomy 16, then trisomy 21 and triploidy, the other chromosomopathy have been trisomy 11, 13, 18, deletion 18, 22, 5 and marker chromosome. Related to the age, 12 (15%) have been older than 35 years, that is 21 (26,2%) 30 years, while the majority have been younger than 30 years 47 (58,8%). In the group of pregnant women where chromosome aberration in chorionic villus have been found, the majority have been non risky age women for chromosomopathy, under 30 years 8 (57%).
We have analysed three blighted ovum, where the conclusion has been parthenogenesis in two cases, and androgenesis in one case.
In 11 pregnant women the miscarriage has been induced, genetic screening on chromosomopathy has been done as well, UZ marker nuchal translucency and biochemical markers PAPP-A/free-beta-HCG from maternal serum. In three cases, anomalies have been determined on ultrasound exam, two anencephalies and one finding of N.T.- 4,6 talipes, swelling of fetal tissues and suspicion on vitium cordis. The other eight miscarriages have had pathology of all three markers of genetic screening. Regarding that these pregnant women have not done the choriocentesis due to the high price of the intervention, as the result from amniocentesis is obtained only in twentieth week of gestation, they have decided to stop the pregnancy in the early period. By cytogenetic analysis of miscarried material, chromosome aberration have been determined in seven cases.
All the chromosome aberration of fetal tissue have indicated karyotypisation of parents from peripheral lymphocyte. Three balanced chromosome aberration have been found with mothers, translocation 46, XX, t 9:16 and 46, XX t 13:21 and 46, XX inv. 5p. One of the pregnant women has been older than 35 years and she had three spontaneous miscarriages, while two pregnant women have been young and this has been their first spontaneous miscarriage.
Out of total 80 analysed miscarriage samples, 53 (66,2%) have had two or more spontaneous miscarriages, while 27 (33,8%) had pathologic result of pregnancy for the first time. By analysis of parents karyotype, it has been noticed that among polymorph markers at 9 (32%) satellite sequences on chromosome 13, 14, 15, 21 and 22 were outstanding, out of which two women have had chromosome 21 and 22 in association. A very large heteromorphic region in Y chromosome has been noticed with one man. It is known based on literature that expressed satellites and heteromorphic region present predisposition for disturbance of chromosome segregation in dividing spindle. The beginning hereditary risk has been determined on the basis of genealogy tree, as well as teratogene risk in the genetic consultation centre. Out of 80 analysed fetuses 35 (43,7%) have had genealogy burden (family anomalies, mental retardations, repeated spontaneous miscarriages), 19 (23,8%) had teratogene burden, while 26 (32,5%) had no hereditary or teratogene burdens. Eleven fetuses with chromosome aberration, in 4 cases hereditary burden have been expressed, while at 7 chromosomopathy have had most probably “by accidentally”.
In practice, after two or more etiologic, not explained spontaneous miscarriages, couples are sent to cytogenetic examination. At our examined sample of chorionic villus and fetal tissues of spontaneous abortions, it has been shown that chromosome aberration has been determined with first miscarriage. It would be desirable to send to cytogenetic analysis the tissue of each miscarried fetus, blighted ovum and other disturbances of embryo development in the first three month period. At confirmed chromosomopathy from fetal tissue, the karyotype of parents should be indicated. It would be the way to find the carrier of balanced changes in chromosome that absolutely induce choriocentesis or amniocentesis in the following pregnancy, regardless the age of pregnant women. The material expenses for direct cytogenetic analysis of miscarriage fetal sample are very low.
Since we have shown, by karyotypisation of fetus, the high level of security of early genetic screening as well, we suggest that each pregnant woman from 10-12 week of gestation should make the determination of three markers nuchal translucency and PAPP-A/free-beta-HCG in maternal serum. In case of pathologic findings, pregnant woman should be sent to choriocentesis or amniocentesis, regardless her age. At our sample of fetal chromosomopathy, the majority have been of pregnant women in young period of life categorized as “non risky”.
|Fetus mors in utero||37||46,3|
|b) pathologic genetic screening||11||13,7|
|Number||Chromosome Aberration||Age||Gestational Week|
|1||47, XX + 11||34||8|
|2||47, XX + 16||34,5||11|
|3||47, XY + 16||24||11|
|4||47, XX + 16||35||9|
|5||47, XX + 21||23||12|
|6||47, XX + 21||38||12|
|7||47, XY + 18||21||12|
|8||47, XY + 13||25||12|
|11||46, XY + M||36||11|
|12||46, XX, del 18 q-||33||8|
|13||46, XX, del 22 q-||27||8|
|14||46, XX del. 5p||29||12|
|Number||Fetus Karyotype||Maternal Karyotype||Paternal Karyotype|
|1||47, XX + 11||46, XX (S-13,14,15,21,22)||46, XY (S-13,14,15,21,22)|
|2||47, XX + 16||46, XX t 9:16||46, XY|
|3||47, XY + 16||46, XX (S-21,22)||46, XY|
|4||47, XX + 16||46, XX||46, XY (S-13,14,15)|
|5||47, XX + 21||46, XX t 13:21||46, XY|
|6||47, XX + 21||46, XX (S-21,22)**||46, XY|
|7||47, XY + 18||46, XX||46, XY|
|8||47, XY + 13||46, XX (S-13,14,15,21,22)||46, XY (S-13,14,15,21,22)|
|9||69, XXX||46, XX (S-13,14,15,21,22)||46, XY|
|10||69, XXX||46, XX||46, XY|
|11||46, XY + M||46, XX||46, XY (Yq> F)*|
|12||46, XX, del 18 q-||46, XX||46, XY|
|13||46, XX, del 22 q-||46, XX (S-21,22)**||46, XY|
|14||46, XX del. 5p-||46, XX inv. 5p***||46, XY|
|S – satellite sequences
* - Yq > F (19-20) chromosome
** - chromosome 21 and 22 in association
***- paracentric inversion 5p
|Number||Fetus Karyotype||MOM PAPP-A||MOM free-beta-HCG||N.T.|
|5||47, XX + 21||0,34||0,25||2,90|
|6||47, XX + 21||0,03||0,30||3,20|
|7||47, XY + 16||0,20||4,04||3,9|
|9||46, XY + M||0,32||3,62||6,50|
|10||47, XX + 16||0,25||0,29||3,70|
|11||47, XX + 18||0,30||3,85||2,80|
** swelling of fetal tissues
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