TRIPLOIDIES IN FIRST AND SECOND TRIMESTERS OF PREGNANCIES IN TURKEY
Yilmaz Z1, Sahin FI1,*, Tarim E2, Kuscu E2
*Corresponding Author: Yilmaz Z1, Sahin FI1,*, Tarim E2, Kuscu E2*Corresponding Author: Professor Dr. Feride Iffet Sahin, Department of Medical Genetics, Faculty of Medicine, Baskent University, Kubilay Sokak No: 36 Maltepe, 06570 Ankara, Turkey; Tel.: +90-312-2324400/138; Fax: +90-312-2319134; E-mail: feridesahin@hotmail.com
page: 71

DISCUSSION

 

 Triploid conceptions die early in development, and account for 10% of all spontaneous abortions [9]. Studies performed on spontaneous abortion tissues revealed that diandric triploidy usually arises as a result of dispermy. Triploid karyotypes may be XXX, XXY or XYY with a ratio of 1:2:1. When the abnormality is in paternal meiosis, first division errors result in the XXY karyotype, whereas second division errors result in XYY and XXX karyotypes, each at about the same frequency. As a result, karyotypes with at least one excess Y chromosome would be expected to occur more frequently. The XYY karyotypes are usually associated with early lethality and spontaneous abortion (4) but this was not observed in spontaneous abortions in the current study, where four XXY karyotypes and one XXX karyotype were found instead.

Cases with low level hCG usually have non molar placentas and are likely to be primarily digynic. Digynic triploidy arises from errors in maternal meiosis and results in XXX and XXY karyotypes with an expected ratio of 1:1, although an excess of XXX cases has been reported [4]. Similarly, three of our second trimester patients had XXX karyotypes and one had a XXY karyotype.

The sex chromosome complement in triploid pregnancies determines the levels of maternal serum hormones and whether the placental phenotype would be molar or non molar. [4]. The XYY triploid karyotypes frequently result in early molar development, while XXY with an intermediate probability and XXX with lowest probability, results in cystic changes and eventually fetal death. The XXX triploids survive longer in utero as a result of a lower but still significant probability for cystic changes. An XXY karyotype could be an explanation for our first trimester spontaneous abortions.

There is no correlation between triploidy and advanced maternal age. In our triploidy cases, maternal ages ranged between 19 and 45 years. Maternal ages were below 35 years in seven of nine triploid cases. Therefore, we concluded that, first and/or second trimester maternal serum screening tests may be more valuable than maternal age when triploidy is regarded.

Second trimester maternal serum hormone analysis has shown high or low levels of hCG, low levels of uE3 and high levels of AFP in triploid pregnancies [6,7,10,11]. Trisomy 18 was associated with a decrease in serum AFP, hCG and uE3 levels in the second trimester of pregnancy [12]. In triploidy, hCG and uE3 values were usually lower than in trisomy 18 [4]. Maternal hCG values as low as 0.01 MoM have been reported. In all our second trimester patients, high risk was observed for trisomy 18 and hCG values ranged between 0.16 and 0.23 MoM.

Triploidy should always be kept in mind in cases at risk according to maternal serum hormone levels. The diagnosis can be rapidly confirmed by molecular cyto genetics of interphase cells. Although cytogenetic analysis is essential in diagnosis of triploidy, parental origin may be detected by molecular genetics methods. Recurrence risk in diandric triploidy associated with partial hydatiform mole has been reported to be 1-1.5% [13]. Parents should be informed about detailed USG scans and prenatal cyto genetic diagnosis in future pregnancies.





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