engleski

Autosomal trisomies - a very important cause of early spontaneous abortions

Spontaneous abortion is defined as the termination of pregnancy before 20th weeks of gestation or below a fetal weight of 500 grams. A total of 321 cases of first trimester spontaneous abortions between 4 and 13 weeks of gestation were analyzed cytogenetically by the direct - preparation method using chorionic villi. A total of 172 (54%) of the specimens were chromosomal abnormal, and 91% were numerical chromosomal abnormalities. The most common abnormalities are trisomies, arising de novo as a result of meiotic non-disjunction during gametogenesis in parents with a normal karyotype. Gonadal mosaicism for trisomies can contribute to recurrent trisomy. Autosomal trisomies comprise 34% of karyotyped spontaneous abortions, and the vast majorities were single trisomies. Trisomies for all chromosomes, with the exception of chromosomes 1, 5, 11, 17 and 19 were observed. Double trisomies [48, XX, +2, +16 ; 48, XX, +16, +18 ; 48, XX, +21, +22] and mosaic trisomy [46, XY/47, XY, +7 ; 46, XX/48, XX, +7, +16 ; 47, XX, +20/48, XX, +7, +20 ; 47, XY, +14/48, XXY, +14] were rare. The most frequent was trisomy 16 (34%), followed by trisomy 22 (11%) and 21 (9%). When abortions were stratified by maternal age, 23% of cases were trisomic in women younger than 35 years of age, and 57% were trisomic in women 35 years or older. This study confirms that the incidence of trisomy increases with maternal age. The mean gestational age was 8-9 weeks. A trisomyc karyotype in chorionic villi from a spontaneous abortion explains the reason for the loss and does not place the couple at higher risk for repeated chromosomal trisomy and pregnancy loss.

autosomal trisomies; spontaneous abortions; cytogenetics

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